Wolff-Parkinson-White Syndrome 

Updated: Jan 08, 2017
Author: Christopher R Ellis, MD, FACC, FHRS; Chief Editor: Mikhael F El-Chami, MD 

Overview

Practice Essentials

In 1930, Wolff, Parkinson, and White described a series of young patients who experienced paroxysms of tachycardia and had characteristic abnormalities on electrocardiography (ECG).[1] Currently, Wolff-Parkinson-White (WPW) syndrome is defined as a congenital condition involving abnormal conductive cardiac tissue between the atria and the ventricles that provides a pathway for a reentrant tachycardia circuit, in association with supraventricular tachycardia (SVT). See the image below for a typical "preexcited" ECG.

Classic Wolff-Parkinson-White electrocardiogram wi Classic Wolff-Parkinson-White electrocardiogram with short PR, QRS >120 ms, and delta wave.

Signs and symptoms

The clinical manifestations of WPW syndrome reflect the associated tachyarrhythmia episodes—rather than the anomalous ventricular excitation per se. They may have their onset at any time from childhood to middle age, and they can vary in severity from mild chest discomfort or palpitations with or without syncope to severe cardiopulmonary compromise and cardiac arrest. Thus, presentation varies by patient age.

Infants may present with the following:

  • Tachypnea
  • Irritability
  • Pallor
  • Intolerance of feedings
  • Evidence of congestive heart failure if the episode has been untreated for several hours
  • A history of not behaving as usual for 1-2 days
  • An intercurrent febrile illness may be present

A verbal child with WPW syndrome usually reports the following:

  • Chest pain
  • Palpitations
  • Breathing difficulty

Older patients can usually describe the following:

  • Sudden onset of a pounding heartbeat
  • Pulse that is regular and “too rapid to count”
  • Typically, a concomitant reduction in their tolerance for activity

Physical findings include the following:

  • Normal cardiac examination findings in the vast majority of cases
  • During tachycardic episodes, the patient may be cool, diaphoretic, and hypotensive
  • Crackles in the lungs from pulmonary vascular congestion (during or following an SVT episode)
  • Many young patients may present with resting tachycardia on examination, with only minimal symptoms (eg, palpitations, weakness, mild dizziness) despite exceedingly fast heart rates

Clinical features of associated cardiac defects may be present, such as the following:

  • Cardiomyopathy
  • Ebstein anomaly
  • Hypertrophic cardiomyopathy ( AMPK mutation) [2]

See Clinical Presentation for more detail.

Diagnosis

Routine blood studies may be needed to help rule out noncardiac conditions triggering tachycardia. These may include the following:

  • Complete blood count
  • Chemistry panel, with renal function studies and electrolytes
  • Liver function tests
  • Thyroid panel
  • Drug screening

The diagnosis of WPW syndrome is typically made with a 12-lead electrocardiogram (ECG) and sometimes with ambulatory monitoring (eg, telemetry, Holter monitoring). SVT is best diagnosed by documenting a 12-lead ECG during tachycardia, although it is often diagnosed with a monitoring strip or even recorder. The index of suspicion is based on the history, and rarely, physical examination (Ebstein anomaly or hypertrophic cardiomyopathy [HOCM]). Although the ECG morphology varies widely, the classic ECG features are as follows:

  • A shortened PR interval (typically <120 ms in a teenager or adult)
  • A slurring and slow rise of the initial upstroke of the QRS complex (delta wave)
  • A widened QRS complex (total duration >0.12 seconds)
  • ST segment–T wave (repolarization) changes, generally directed opposite the major delta wave and QRS complex, reflecting altered depolarization

Echocardiography is needed for the following:

  • Evaluation of left ventricular (LV) function, septal thickness, and wall motion abnormalities
  • Excluding cardiomyopathy and an associated congenital heart defect (eg, HOCM, Ebstein anomaly, L-transposition of the great vessels)

Stress testing is ancillary and may be used for the following:

  • To reproduce a transient paroxysmal SVT, which is triggered by exercise
  • To document the relationship of exercise to the onset of tachycardia
  • To evaluate the efficacy of antiarrhythmic drug therapy (class Ic antiarrhythmic medications and effects on antegrade preexcitation)
  • To determine whether consistent or  intermittent preexcitation is present at different sinus (heart) rates

Electrophysiologic studies (EPS) can be used in patients with WPW syndrome to determine the following:

  • The mechanism of the clinical tachycardia
  • The electrophysiologic properties (eg, conduction capability, refractory periods) of the accessory pathway and the normal atrioventricular (AV) nodal and His Purkinje conduction system
  • The number and locations of accessory pathways (necessary for catheter ablation)
  • The response to pharmacologic or ablation therapy

See Workup for more detail.

Management

Treatment of WPW associated arrhythmias comprises the following:

  • Radiofrequency ablation of the accessory pathway [3]
  • Antiarrhythmic drugs to slow accessory pathway conduction
  • AV nodal blocking medications in adult patients to slow AV nodal conduction in certain situations (ie, Mahaim or atriofascicular pathway-mediated SVT; typically, AV node-conduction blocking medications are avoided in the acute setting of WPW)
  • For adult WPW patients, address the triggers that perpetuate the dysrhythmia, which include coronary heart disease (CAD), ischemia, cardiomyopathy, pericarditis, electrolyte disturbances, thyroid disease, and anemia

Termination of acute episodes

Narrow-complex AV reentrant tachycardia (AVRT) and AV nodal reentrant tachycardia (AVNRT) are treated by blocking AV node conduction with the following:

  • Vagal maneuvers (eg, Valsalva maneuver, carotid sinus massage, splashing cold water or ice water on the face)
  • Adults: IV adenosine 6-12 mg via a large-bore line (the drug has a very short half-life)
  • Adults: IV verapamil 5-10 mg or diltiazem 10 mg
  • Pediatric patients: Adenosine and verapamil or diltiazem are dosed on the basis of weight.

Atrial flutter/fibrillation or wide-complex tachycardia is treated as follows:

  • IV procainamide or amiodarone if wide-complex tachycardia is present, ventricular tachycardia (VT) cannot be excluded, and the patient is stable hemodynamically
  • Ibutilide

The initial treatment of choice for hemodynamically unstable tachycardia is direct-current synchronized electrical cardioversion, biphasic, as follows:

  • A level of 100 J (monophasic or lower biphasic) initially
  • If necessary, a second shock with higher energy (200 J or 360 J)

Radiofrequency ablation

Radiofrequency ablation is indicated in the following patients:

  • Patients with symptomatic AVRT
  • Patients with AF or other atrial tachyarrhythmias that have rapid ventricular response via an accessory pathway (preexcited AF)
  • Patients with AVRT or AF with rapid ventricular rates found incidentally during EPS for unrelated dysrhythmia, if the shortest preexcited RR interval during AF is less than 250 ms [4]
  • Asymptomatic patients with ventricular preexcitation whose livelihood, profession, insurability, or mental well-being may be influenced by unpredictable tachyarrhythmias or in whom such tachyarrhythmias would endanger the public safety [5]
  • Patients with WPW and a family history of sudden cardiac death

Surgical treatment

Radiofrequency catheter ablation has virtually eliminated surgical open heart treatments in the vast majority of WPW patients, with the following exceptions:

  • Patients in whom RF catheter ablation (with repeated attempts) fails
  • Patients undergoing concomitant cardiac surgery (possible exception)
  • Patients with other tachycardias with multiple foci who require surgical intervention (very rare)

Long-term antiarrhythmic therapy

Oral medication is the mainstay of therapy in patients not undergoing radiofrequency ablation, although the response to long-term antiarrhythmic therapy for the prevention of further episodes of tachycardia in patients with WPW syndrome remains quite variable and unpredictable. Choices include the following:

  • Class Ic drugs (eg, flecainide, propafenone), typically used with an AV nodal blocking agent in low doses to avoid atrial flutter with a 1:1 conduction
  • Class III drugs (eg, amiodarone, sotalol), although these are less effective for altering accessory pathway conduction properties
  • In pregnancy, sotalol (class B) or flecainide (class C)

See Treatment and Medication for more detail.

Background

In 1930, Wolff, Parkinson, and White described a series of young patients who had a bundle branch block pattern on electrocardiography (ECG) findings, a short PR interval, and paroxysms of tachycardia.[1] Case reports began appearing in the literature in the late 1930s and early 1940s, and the term Wolff-Parkinson-White (WPW) syndrome was coined in 1940.

Although "preexcitation" was first coined by Ohnell in a landmark publication in 1944, the term as defined by Durrer et al in 1970 provided a better description in the literature of what an accessory pathway is (before the advent of invasive electrophysiologic studies and ablation provided a clearer understanding): "Preexcitation exists, if in relation to atrial events, the whole or some part of the ventricular muscle is activated earlier by the impulse originating from the atrium than would be expected if the impulse reached the ventricles by way of the normal specific conduction system only."[6]

WPW syndrome is currently defined as a congenital abnormality involving the presence of abnormal conductive cardiac tissue between the atria and the ventricles in association with supraventricular tachycardia (SVT). It involves preexcitation, which occurs because of conduction of an atrial impulse not by means of the normal conduction system, but via an extra atrioventricular (AV) muscular connection, termed an accessory pathway (AP), that bypasses the AV node.[4, 7]

Classic ECG findings that are associated with WPW syndrome include the following:

  • Presence of a short PR interval (<120 ms)
  • A wide QRS complex longer than 120 ms with a slurred onset of the QRS waveform, termed a delta wave, in the early part of QRS
  • Secondary ST-T wave changes (see the image below)
Classic Wolff-Parkinson-White electrocardiogram wi Classic Wolff-Parkinson-White electrocardiogram with short PR, QRS >120 ms, and delta wave.

Patients with WPW syndrome are potentially at an increased risk of dangerous ventricular arrhythmias as a consequence of conduction across the bypass tract resulting in a very rapid and chaotic depolarization of the ventricle if they develop atrial flutter or atrial fibrillation (AF).

Some patients have a concealed bypass tract. Although they have an accessory AV connection, it lacks antegrade conduction; accordingly, these patients do not have the classic abnormalities of the surface ECG. Most commonly, this is established by electrophysiologic study performed for the evaluation or treatment of  SVT.

Only a small percentage of patients with WPW syndrome (<1%) are at risk for sudden cardiac death (SCD). In patients who present with preexcited AF, cardiac electrophysiologic studies and radiofrequency (RF) catheter ablation may be curative. Other presentations include symptomatic SVT, which can also be cured by catheter ablation. Asymptomatic patients need periodic observation. The onset of cardiac arrhythmias, and possibly the sudden death risk, may be eliminated by prophylactic catheter ablation as well.[8]

This review discusses the pathogenesis, clinical presentation, evaluation, and treatment of patients with WPW syndrome.

Pathophysiology

Accessory pathways or connections between the atrium and ventricle are the result of anomalous embryonic development of myocardial tissue bridging the fibrous tissues that separate the two chambers. This allows electrical conduction between the atria and ventricles at sites other than the AV node. Passage through APs circumvents the usual conduction delay between the atria and ventricles, which normally occurs at the AV node, and predisposes the patient to develop tachydysrhythmias.

Although dozens of locations for bypass tracts can exist in preexcitation, including atriofascicular, fasciculoventricular, nodofascicular, or nodoventricular, the most common bypass tract is an accessory AV pathway otherwise known as a Kent bundle. This is the anomaly seen in WPW syndrome. The primary feature that differentiates WPW syndrome from other AP-mediated supraventricular tachycardias (SVTs) is the ability of the AP to conduct in either an antegrade (ie, from atrium to ventricles) or a retrograde manner.

The presence of an AP sets up the potential for reentrant tachycardia circuits to be established or for preexcited tachycardia in the setting of atrial fibrillation, atrial flutter, or SVT with a bystander accessory pathway. This reentrant mechanism is the typical cause of the SVT of which patients with preexcitation are at risk. The genesis of reentrant SVT involves the presence of dual conducting pathways between the atria and the ventricles[9] :

  • The natural AV nodal His-Purkinje tract
  • One or more AV accessory tract(s) (ie, AV connection or AP, Kent fibers, Mahaim fibers)

These pathways usually exhibit different conduction properties and refractory periods that facilitate reentry. The effective refractory period (ERP, the time necessary for the electrical recovery needed to conduct the next impulse) of the accessory tract is often longer than that of the normal AV nodal His-Purkinje tract and requires time for conduction to recover before allowing reentry.

The degree of preexcitation on a surface ECG in a person with WPW pattern can be estimated by the width of the QRS and the length of the PR interval. A wider or more preexcited QRS with a short PR interval with absent or nearly absent isoelectric component reveals that most (or all) of the ventricular depolarization initiates through the AP insertion rather than through the AV node/His Purkinje system. This would be typical with right free wall pathways where the atrial insertion is close to the sinoatrial (SA) node.

However, the QRS width may vary, becoming narrower during more rapid heart rates. This is possible because catecholamines permit the AV node to contribute more (or entirely) to ventricular depolarization by enhancing AV node conduction; the AV node connects to the entire and usual His-Purkinje system, resulting in the narrow QRS complex.

Types of SVT include orthodromic tachycardia (down the AV nodal His-Purkinje system and retrograde conduction up an AP), orthodromic tachycardia with a concealed AP (retrograde conduction only), and antidromic tachycardia (down the AP and retrograde conduction up the His-Purkinje system and AV node). In patients with WPW in which the AP participates in the reentrant circuit, 95% of SVT is due to orthodromic tachycardia and 5% is due to antidromic tachycardia.

Orthodromic tachycardia

When a premature ectopic atrial impulse advances towards the ventricle, it has the potential to block at the AP but conduct down the normal AVN/His Purkinje pathway. The impulse then reenters the AP in a retrograde fashion to perpetuate a circus movement of the impulse. Such reentrant tachycardia is described as orthodromic. Premature ventricular contractions (PVCs) can also initiate orthodromic tachycardia.

In orthodromic tachycardia, the normal pathway is used for ventricular depolarization, and the AP is used for the retrograde conduction essential for reentry. On ECG findings, the delta wave is absent, the QRS complex is normal, and P waves are typically inverted in the inferior and lateral leads.

Orthodromic tachycardia with concealed accessory pathway

Some APs are unable to conduct in an antegrade fashion. These are called concealed APs, because "manifest" preexcitation is a delta wave that is visible on a surface 12-lead ECG. (Technically, concealed pathways should not be classifed as a WPW syndrome, because there is no delta wave.) They account for about 30% of all SVTs induced on EPS.

Although no evidence of the pathway is present during sinus rhythm (ie, no preexcitation on ECG), orthodromic tachycardias can occur. Orthodromic tachycardia may also occur when there are two or more accessory connections, and in that case, the retrograde conduction may occur through the AV node, through one of the accessory connections, or through both.

This type of SVT may be difficult to distinguish from the usual AV nodal reentrant tachycardia (AVNRT) on a standard surface ECG. In adults, if the heart rate is higher than 200 bpm or a retrograde P wave is visible in the ST segment (long R-P tachycardia), a concealed AP-mediated orthodromic reentrant tachycardia (ORT) may be the diagnosis. However, this determination is most accurately made with electrophysiologic studies (EPS), or if SVT terminates with a single PVC. Other differentiating factors include the following[10] :

  • Anterior AVNRT: Presence of pseudo r' wave in lead V1, or a pseudo S wave in leads II, III, and aVF
  • Posterior AVNRT: Presence of a more than 20-ms difference in R-P interval between leads I and III
  • AVNRT: Presence of an AV block or AV dissociation (uncommon and of short duration) excludes the presence of an AP; development of a bundle branch block with an unchanged atrial-atrial (AA) or His-His (HH) interval
  • Orthodromic AVRT: Development of a bundle branch block in the presence of a significant change in the ventriculoatrial (VA) interval (diagnostic), with localization of the AP to the same side as the block. 

Antidromic tachycardia

Less commonly, a shorter refractory period in the AP may cause blockade of an ectopic atrial impulse in the normal pathway, with antegrade conduction down the AP and then retrograde reentry of the normal AV nodal pathway. This type of tachycardia is called antidromic tachycardia.

On ECG, the QRS is wide, reflecting an exaggeration of the delta wave during sinus rhythm (ie, wide-QRS tachycardia). Such tachycardias are difficult to differentiate from ventricular tachycardias and often have a slurred R wave upstroke with QRS duration longer than 160 ms.

Only about 5% of the tachycardias in patients who have WPW syndrome are antidromic tachycardias; the remaining 95% are orthodromic. Even when the AP conducts solely in a retrograde fashion, it can still participate in the reentrant circuit and produce an orthodromic AV reciprocating tachycardia with a narrow QRS morphology. The presence of an antidromic tachycardia should prompt a careful search for a second bypass tract.[10, 11]  About 10-15% of patients with WPW have a second pathway.[11]

Etiology

APs are considered congenital phenomena that are related to a failure of insulating tissue maturation within the AV ring—even though their manifestations are often detected in later years, making them appear to be "acquired." On rare occasions, acquired WPW syndrome has occurred in patients who have undergone congenital heart surgery, which may be owing to an acquired functional epicardial AV connection.[12]

Family studies, as well as molecular genetic investigations, indicate that WPW syndrome, along with associated preexcitation disorders, may have a genetic component. It may be inherited as a familial trait, with or without associated congenital heart defects (CHDs)[13] ; 3.4% of those with WPW syndrome have first-degree relatives with preexcitation.

The familial form is usually inherited as a mendelian autosomal dominant trait. Although rare, mitochondrial inheritance has also been described. The syndrome may also be inherited with other cardiac and noncardiac disorders, such as familial atrial septal defects, familial hypokalemic periodic paralysis, and tuberous sclerosis.

Clinicians have long recognized the association of WPW syndrome with autosomal dominant familial hypertrophic cardiomyopathy. However, only comparatively recently was a genetic substrate linking hypertrophic cardiomyopathy to WPW syndrome and skeletal myopathy described.[2]

Patients with mutations in the gamma 2 subunit of adenosine monophosphate (AMP)-activated protein kinase (PRKAG2) develop cardiomyopathy characterized by ventricular hypertrophy, WPW syndrome, AV block, and progressive degenerative conduction system disease. The mutation is believed to produce disruption of the annulus fibrosus by accumulation of glycogen within myocytes, which causes preexcitation. This is thought to be the case in Pompe disease, Danon disease, and other glycogen-storage diseases.

Infantile Pompe disease or glycogen-storage disease type II is a fatal genetic muscle disorder that is caused by deficiency of acid alpha-glucosidase (GAA). These patients have a shortened PR interval, large left ventricular (LV) voltages, and an increased QT dispersion (QTd).

More recently, investigators appeared to have identified a novel locus in a family with WPW, MYH6 p.E1885K.[14] All of the family members with WPW but none of the unaffected relatives demonstrated this variant. MYH6 variants have been associated with atrial septal defects, cardiomyopathies, and sick sinus syndrome.[14]

Mutations in the lysosome-associated membrane protein 2 (LAMP2), which cause accumulation of cardiac glycogen, are thought to be the etiology of a significant number of hypertrophic cardiomyopathies in children, especially when skeletal myopathy, WPW syndrome, or both are present.

For example, Danon disease is an X-linked lysosomal cardioskeletal myopathy; males are more often and more severely affected than females. It is caused by mutations in the LAMP2 that produce proximal muscle weakness and mild atrophy, left ventricle hypertrophy, WPW syndrome, and mental retardation.

Patients with the Ebstein anomaly may develop WPW syndrome. They frequently have multiple accessory bypass tracts, mostly on the right, in the posterior part of the septum or the posterolateral wall of the right ventricle. The orthodromic reciprocating tachycardia in such patients often exhibits right bundle-branch block (RBBB) and a long ventriculoatrial (VA) interval.

Preexcitation can be surgically created, as in certain types of Bjork modifications of the Fontan procedure, if atrial tissue is flapped onto and sutured to ventricular tissue. Certain tumors of the AV ring, such as rhabdomyomas, may also cause preexcitation.

Epidemiology

United States statistics

The prevalence of ventricular preexcitation is thought to be 0.1-0.3%, or 1-3 per 1000 people in the general population. Estimates of arrhythmia incidence in patients with preexcitation vary widely, ranging from 12% to 80% in several surveys.

The incidence of preexcitation and WPW syndrome ranges from 0.1 to 3 cases per 1000 population (average, 1.5 cases per 1000 population) in otherwise healthy persons. This includes only patients with manifest preexcitation (delta wave evident on surface 12-lead ECG). About 60-70% of these individuals have no other evidence of heart disease. Approximately four newly diagnosed cases of WPW syndrome per 100,000 population occur each year.

In a review of ECG findings from 22,500 healthy aviation personnel, 0.25% exhibited findings consistent with the WPW pattern, with a 1.8% reported incidence of tachycardia.

The location of the accessory pathways (APs), in descending order of frequency, is (1) 53%, the left free wall, (2) 36%, posteroseptal, (3) 8%, right free wall, and (4) 3%, anteroseptal. The presence of concealed APs accounts for approximately 30% of patients with apparent SVT referred for electrophysiologic studies (EPS). These patients do not have "classic" WPW syndrome because no delta wave is present, but they do have the potential for orthodromic tachycardia.

Approximately 80% of patients with WPW syndrome have a reciprocating tachycardia, 15-30% will develop atrial fibrillation (AF), and 5% have atrial flutter. VT is uncommon. Patients with mitral valve prolapse have an association with WPW, but the mechanism is unclear.

International statistics

Worldwide, the incidence and prevalence of WPW syndrome parallel those seen in the United States.

Age-related demographics

WPW syndrome is found in persons of all ages. Most patients with WPW syndrome present during infancy. However, a second peak of presentation is noted in school-aged children and in adolescents. This interesting bimodal age distribution is due to permanent or transitory loss of preexcitation during infancy in some patients and during late adolescence in others.

The prevalence of WPW syndrome decreases with age as a consequence of apparent attenuation of conduction speed in the AP. About one fourth of patients lose preexcitation over a 10-year period, probably as a result of fibrotic changes at the site of insertion of the accessory bypass tract with loss of electrical conduction properties between cardiac chambers. Cases have been described in which ECG evidence of preexcitation disappears completely. One tenth of patients with concealed APs lose retrograde conduction over 10 years.

In asymptomatic patients, antegrade conduction across the AP may spontaneously disappear with advancing age (one fourth of patients lose antegrade bypass tract conduction over 10 years).

In patients with abnormal ECG findings indicative of WPW syndrome, the frequency of SVT paroxysms increases from 10% in people aged 20-39 years to 36% in people older than 60 years.[15] Overall, about 50% of patients with WPW develop tachyarrhythmias.

Sex-related demographics

WPW pattern appears to affect the two sexes equally; however, WPW syndrome has been found to be more frequent in males. One study documented a male-to-female ratio of approximately 2:1. Another reported 1.4 cases of WPW syndrome per 1000 men and 0.9 cases per 1000. A third study found a 3.5-fold higher prevalence of WPW syndrome in men.

Race-related demographics

No clear racial predilection appears to exist.

Prognosis

Once identified and appropriately treated, WPW syndrome is associated with an excellent prognosis, including the potential for permanent cure through radiofrequency (RF) catheter ablation.

Asymptomatic patients with only preexcitation on ECG generally have a very good prognosis. Many develop symptomatic arrhythmias over time, which can be prevented with prophylactic EPS and RF catheter ablation.[16] Patients with a family history of sudden cardiac death (SCD) or significant symptoms of tachyarrhythmias or cardiac arrest have worse prognoses. However, once definitive therapy is performed, including curative ablation, the prognosis is once again excellent.

Noninvasive risk stratification (eg, Holter monitoring, exercise stress test)[17] can be useful if abrupt and complete loss of preexcitation occurs with exercise or procainamide infusion. However, this is not an absolute predictor for the absence of arrhythmic episodes. 

Mortality/morbidity

Mortality in WPW syndrome is rare and is related to SCD. The incidence of SCD in WPW syndrome is approximately 1 in 100 symptomatic cases when followed for up to 15 years. Although relatively uncommon, SCD may be the initial presentation in as many as 4.5% of cases.

Even in patients with asymptomatic WPW, the risk of SCD is increased above that of the general population. Medical therapy with agents such as digoxin may increase this risk if the patient has AF or atrial flutter by favoring atrial-to-ventricular conduction over the bypass tract rather than the AV node. The risk in asymptomatic patients is low and can be reduced further with prophylactic catheter ablation of the accessory pathway (EPS and RF ablation).

Other factors that appear to influence the risk of SCD are the presence of multiple bypass tracts, short AP refractory periods (<240 ms), AF and atrial flutter, or a family history of premature sudden death. SCD is unusual without preceding symptoms.

The cause of SCD in WPW syndrome is rapid conduction of AF to the ventricles via the AP, resulting in ventricular fibrillation (VF). AF develops in one fifth to one third of patients with WPW syndrome; the reasons for this and the effects of AP ablation on its development are unclear.

However, a study hypothesized that two mechanisms are involved in the pathogenesis of AF in patients with WPW syndrome: one is related to the AP that predisposes the atria to fibrillation, and the other is independent from the AP and is related to increased atrial vulnerability present in these individuals.[18]  Notably, AF may still occur and be symptomatic in some patients after successful ablation of the bypass tract,[11, 19]  but AF does not then carry the same associated risk of SCD.

In a study that evaluated the long-term (median, 6.9 y) natural history of WPW in adult patients treated with (n = 872) and without catheter ablation (n = 1461) compared to a control group (n = 11,175), Bunch et al found similarly low death rates but higher incident AF risk in patients with WPW versus the control group.[20]  The risk of long-term mortality was higher in those who did not undergo ablation compared to the group treated with ablation, whereas the risk of incident AF was higher in the ablation group. Thus, ablation did not reduce the risk of AF.

According to the literature, risk factors for the development of AF in the setting of WPW syndrome include advancing age (two peak ages for AF occurrence are recognized, one at 30 years and the other at 50 years), male sex, and prior history of syncope.[21]

Certain factors increase the likelihood of VF, including rapidly conducting APs and multiple pathways.[22] Cases have also been reported in association with esophageal studies, digoxin, and verapamil. A few reports document spontaneous VF in WPW syndrome, and SVT may degenerate into AF, thus leading to VF[23] ; however, both scenarios are rare in pediatric patients.

Morbidity may be related to rapid near syncope or syncopal arrhythmias. Even when syncope is absent, the arrhythmia episodes may be highly symptomatic. In most patients, the SVT is well tolerated and is not life threatening. However, the potential for syncope, hemodynamically compromising rhythms, or sudden death may prevent patients with WPW syndrome from participating in competitive sports or hazardous occupations until the substrate is definitively addressed and cured by a catheter ablation procedure.

Complications

Complications include the following:

  • Tachyarrhythmia
  • Palpitations
  • Dizziness or syncope
  • Sudden cardiac death
  • Complications of drug therapy (eg, proarrhythmia, organ toxicity)
  • Complications associated with invasive procedures and surgery
  • Recurrence

Patient Education

Patient education is of paramount importance in patients with WPW syndrome. This is especially true in asymptomatic young patients who have been told of their abnormal ECG results. Periodic follow-up care of such patients is necessary, along with thoughtful discussions of consideration for EPS and prophylactic catheter ablation.

Urge patients to carry a sample ECG in sinus rhythm and a medical identification bracelet in case of cardiac arrest.

Educate patients who are being treated with drug therapy thoroughly regarding the disease and the type of medications they are taking. Such patients must be taught the following:

  • How to recognize disease recurrence
  • How to perform vagal maneuvers, when needed
  • To keep their follow-up appointments
  • To identify the adverse effects of antiarrhythmic drugs
  • Typically, to avoid aggressive competitive sports
  • To learn about ablative options and the indications for ablation

Patients with WPW syndrome should also educate their family members, and their siblings should be screened for preexcitation with 12-lead ECG.

For patient education resources, see the Heart Center, as well as Supraventricular Tachycardia.

 

Presentation

History

Patients with Wolff-Parkinson-White (WPW) syndrome may present with anything from mild chest discomfort or palpitations with or without syncope to severe cardiopulmonary compromise or cardiac arrest.

An infant with WPW syndrome may frequently be irritable, may not tolerate feedings, or may demonstrate evidence of congestive heart failure (CHF). Infants often have a history of not behaving as usual for 1-2 days. An intercurrent febrile illness is often observed.

A verbal child with WPW syndrome usually reports chest pain, palpitations, or breathing difficulty. Most children are previously well, and a minority of children have a positive family history of this condition.

Older patients can usually describe the sudden onset of a pounding heartbeat, which is regular and “too rapid to count.” This is typically accompanied by a concomitant change in their tolerance for activity. An irregular rhythm may herald the presence of atrial fibrillation (AF). Occasionally, evidence of disease is discovered on routine electrocardiography (ECG), independent of a concurrent tachydysrhythmia.

In patients with WPW syndrome, the tachycardia that produces symptoms may be a supraventricular tachycardia (SVT), AF, or atrial flutter. In a series of 212 patients with tachyarrhythmias and WPW syndrome, SVT alone occurred in 64%, AF alone occurred in 20%, and both occurred in 16% of patients.

SVT in WPW syndrome may begin in childhood or may not appear clinically until the patient reaches middle age. The clinical course can be unpredictable, as SVT induction depends upon changes in accessory pathway and often AV node EP properties that can vary with time.

SVT due to reentry in WPW is typically orthodromic tachycardia in 95% and antidromic tachycardia in 5% (see Pathophysiology). Orthodromic SVT is usually well tolerated and not a high risk, especially in the pediatric population after young infancy. Antidromic SVT presents more frequently with dizziness and syncope. In addition, it may precipitate ventricular tachycardia and ventricular fibrillation (VF).

Light-headedness and near syncope appear to occur more commonly in persons with WPW syndrome who have paroxysmal SVT (PSVT) or atrial fibrillation than in those with atrioventricular (AV) nodal reentry.

Syncope can occur because of inadequate cerebral circulation due to a rapid ventricular rate or because the tachyarrhythmia is depressing the sinus pacemaker, causing a period of asystole at the point of tachycardia termination.

PSVT can be followed after termination by polyuria, which is due to atrial dilatation and release of atrial natriuretic factor.

Physical Examination

WPW syndrome has no specific examination features except for those that may accompany symptomatic dysrhythmias. The vast majority of WPW patients have normal cardiac examination findings.

Many young patients appear may present with resting tachycardia on physical examination, with only minimal symptoms (eg, palpitations, weakness, mild dizziness) despite exceedingly fast heart rates. Upon physical examination, the patient may be cool, diaphoretic, and hypotensive. Crackles in the lungs are common because the rapid heart rate may cause pulmonary vascular congestion due to CHF.

During SVT, the rhythm is unvarying and regular, with constant intensity of the first heart sound. The jugular venous pressure can be elevated, but the waveform generally remains constant.

An infant experiencing an episode of SVT is usually tachypneic and irritable; pallor is common. The pulse is very rapid and diminished in volume. The ventricular rate typically is 200-250 bpm, and the blood pressure is decreased. If the episode has been untreated for several hours, the patient often has poor perfusion, hepatomegaly, and cardiac failure. The child is usually anxious but hemodynamically stable. Tachypnea often accompanies the tachycardia.

Once the arrhythmia has been terminated, the physical examination findings are generally normal.

Clinical features of associated cardiac defects may be present, such as the following:

In the presence of congenital heart defects (CHDs) or cardiomyopathy, findings of the underlying condition often become apparent only after the SVT has been terminated, although the hemodynamic consequences may be poorly tolerated.

In several series, the incidence of associated congenital heart disease is reported to be as high as 30%, most commonly Ebstein anomaly of the tricuspid valve and corrected transposition of the great arteries.

Approximately 10% of patients with Ebstein anomaly of the tricuspid valve have WPW syndrome. They usually have more than 1 accessory pathway (AP), and those are usually on the right side. Patients with corrected transposition of the great arteries and left-side Ebstein anomaly may also have WPW syndrome. In these patients, the AP is on the left side or septal.

Patients with Ebstein anomaly of the tricuspid valve may present with cyanosis, tachypnea, and other signs of congestive heart failure in presence of a rapid heart rate. ECG may show either wide or narrow QRS, SVT, and, sometimes, QRS with changing morphology if more than one AP is present. Patients with right-side accessory pathways should be screened for the Ebstein anomaly by echocardiography.

Patients with glycogen-storage diseases have muscle weakness with normal or increased muscle bulk, macroglossia and hepatomegaly in the case of Pompe disease, and mental retardation in case of Danon disease.

Other congenital heart diseases associated with WPW syndrome include atrial and ventricular septal defects and coronary sinus diverticula.

The abnormal QRS complexes of WPW syndrome, when present, may appear similar to those observed in acute myocardial infarction (MI), left ventricular hypertrophy (LVH), and hypertrophic cardiomyopathy. Repolarization abnormalities are common in patients with WPW syndrome, and thus, acute MI and LVH cannot be diagnosed if a delta wave is present.

 

DDx

Diagnostic Considerations

Wolff-Parkinson-White (WPW) syndrome can result in supraventricular tachycardia (SVT) that uses an arteriovenous accessory pathway (AP). The AP may also act as an innocent bystander and allow conduction during other supraventricular dysrhythmias, such as atrial fibrillation (AF) or atrial flutter. Paradoxically, the use of digoxin and perhaps other atrioventricular (AV) nodal blocking agents may favor conduction through the AP, causing potentially lethal ventricular dysrhythmias (ventricular fibrillation [VF]) or hemodynamic instability during AF.

The most common mechanism in pediatric patients is AP-mediated SVT, which is a reentrant tachycardia. The main differential during SVT is whether the AP is concealed (ie, conducts only from ventricle to atrium) and thus is an SVT with narrow QRS.

An automatic mechanism may be differentiated from reentry by the following:

  • Presence of a warmup or cool-down period (which is due to its relation with catecholamine levels)
  • Inability to initiate or terminate SVT with programmed atrial stimulation
  • Usual unresponsiveness to electrical cardioversion

A regular tachycardia of sudden onset and termination that allows for some cycle-length oscillation (which can be usually initiated and terminated with programmed atrial stimulation) and that is usually responsive to electrical cardioversion favors a reentrant mechanism.

Differential diagnosis of accessory pathway syndromes

Few entities that involve paroxysms of SVT with a WPW pattern electrocardiogram (ECG) in sinus rhythm may be differentiated from AP-mediated SVT. Examples include the following:

  • Low atrial focus, which occasionally produces the appearance of a short PR interval
  • Atriofascicular APs (so-called Mahaim fibers)
  • Lown-Ganong-Levine (LGL) syndrome

The term “Mahaim fibers” refers to atriofascicular bypass tracts that connect the right atrium to the distal right bundle (see the image below). These pathways usually represent a duplication of the AV node and the distal conducting system. They typically occupy the right ventricular free wall. Their proximal end resides adjacent to the lateral tricuspid annulus and exhibits slow conduction, with AV node–like characteristics. The distal end, which conducts rapidly, inserts into the distal right bundle branch or the apical region of the right ventricle.

Variants of Wolff-Parkinson-White syndrome (unusua Variants of Wolff-Parkinson-White syndrome (unusual accessory pathways).

If Mahaim fibers are present, the ECG findings are a normal or long PR interval and an abnormally wide QRS complex with a left-bundle appearance. Preexcitation may not be apparent during sinus rhythm but can be demonstrated with premature right atrial stimulation. Because retrograde conduction is absent, only an antidromic AV reentry tachycardia (ie, preexcited tachycardia) can develop.

In the presence of atriofascicular tracts, preexcited tachycardia has a left bundle-branch block (LBBB) pattern, a long AV interval (due to the long conduction time over the accessory pathway), and short ventriculoatrial (VA) intervals. If right bundle-branch block (RBBB) develops, it may prolong the tachycardia cycle length (slow the AV reentrant tachycardia [AVRT]). Any right free wall bypass tract-mediated SVT will be prolonged with RBBB but should be unaffected by LBBB aberrancy.

Conversely, left free wall bypass tract AVRT will slow with LBBB (ipsilateral to the accessory pathway). Septal pathways may be slightly affected by either RBBB (anteroseptal) or LBBB (posteroseptal), but this would be detected only on electrophysiologic study (EPS). The eponym Coumel is also applied to this rule.

Given the pathway length and decremental conduction properties (similar to AV nodal conduction), a preexcited QRS complex with a short PR interval essentially rules out Mahaim fibers.

In LGL syndrome, patients have a short PR interval and SVT but no delta wave. This is typically caused by an atrio-Hisian pathway leading to accelerated AV conduction, but not causing paroxysmal SVT. In patients with LGL syndrome who have an atrio-Hisian tract, the QRS complex remains normal and the short atrio-Hisian interval remains fixed during atrial pacing at rapid rates.

Entities that involve wide-QRS SVT must be differentiated from ventricular tachycardia (VT). Examples include the following:

  • Aberrantly conducting orthodromic SVT, which is wide-QRS SVT with the AV node as the antegrade limb but with bundle branch block, must be differentiated from VT
  • Antidromic tachycardia, which is wide-QRS SVT due to ventricular preexcitation through an AP, must also be differentiated from VT and from Mahaim fiber tachycardia

Sometimes, accessory AV fibers connect to the AV node itself or the His bundle or bundle branches and insert into the ventricular myocardium. These are called nodoventricular or fasciculoventricular tracts. Patients with fasciculoventricular connections show a short His-ventricle (HV) interval and no change in the QRS complex during rapid atrial pacing. Fasciculoventricular AV pathways do not participate in clinically meaningful arrhythmias.

Other forms of tachycardia in patients with WPW syndrome

Patients with WPW syndrome can have other tachycardias where the AP is just a bystander, such as atrioventricular nodal reentrant tachycardia (AVNRT) or atrial tachycardia that conducts to the ventricle over the bypass tract.

Atrial flutter or AF may also occur in the atrium, unrelated to the AP, and can conduct rapidly to the ventricle. Patients with WPW syndrome who have AF frequently have inducible reciprocating tachycardias. Interruption of the AP with ablation may or may not prevent recurrence of the AF.

AF presents a potentially serious risk. It typically has a cycle length of 120-200 ms or 300-500 bpm. Atrial flutter is typically at a cycle length of 200 ms or 300 bpm. At rapidly conducted rates (ie, a rate faster than 250 bpm or an AP refractory period shorter than 240 ms), the risk of sudden death occurs as a result of potential conversion from rapid AF to VF. However, such a phenomenon is uncommon, occurring at an estimated frequency of about less than 0.1%.

Patients who have intermittent preexcitation or those who lose ECG evidence of preexcitation abruptly with exercise or when injected intravenously with procainamide generally have a long AP refractory period. These patients are thought to have a low risk of developing a rapid ventricular rate should atrial flutter or AF develop (see the image below).

Preexcited atrial fibrillation. Preexcited atrial fibrillation.

However, a more recent study suggested that children with intermittent preexcitation do not have a lower-risk APs as measured by EPS criteria or reduced symptoms.[24] The investigators evaluated data from 295 children (1996-2013), comparing those with persistent, intermittent, or loss of preexcitation Holter/Holter testing. Although there were no baseline differences in high-risk pathways among these groups, the inclusion of isoproterenol values demonstrated an increased frequency of high-risk pathways among children with loss of preexcitation on Holter/Holter testing (54% vs 16% persistent, 11% intermittent).

Differential Diagnoses

 

Workup

Approach Considerations

The extent of the workup is determined by the acuity of the patient’s illness. In the patient who has cardiogenic shock or is unconscious, direct-current (DC) cardioversion is indicated as soon as a dysrhythmia is identified to be causative. Once the patient is hemodynamically stable or in the context of assessment following an arrest, selected laboratory studies may be considered.

No specific diagnostic laboratory studies are indicated. If laboratory values are obtained, it is reasonable to check electrolytes, including potassium, magnesium, and calcium, which may all potentially contribute to dysrhythmias. Assessment of arterial blood gases, electrolyte levels, and lactate levels may be appropriate, as well as drug screening.

The diagnosis of Wolff-Parkinson-White (WPW) syndrome is typically made with formal electrocardiographic (ECG) monitoring in conjunction with clues from the history and physical examination. Evaluate patients presenting with symptomatic tachycardia (supraventricular tachycardia [SVT] or wide-complex tachycardia) for the presence of preexcitation on the 12-lead ECG results, and consider consultation with a cardiac electrophysiologist. Noninvasive mapping of cardiac arrhythmias is also possible with a 252-lead ECG and computed tomography (CT)-based three-dimensional (3D) electroimaging.[25]

Evaluate patients with WPW syndrome for the presence of very short refractory periods, because these patients carry higher probabilities of developing symptoms or complications. The patients also respond poorly to drug therapy. Identify these patients, even if asymptomatic, and treat them aggressively using electrophysiologic study (EPS) and ablative therapy.

Laboratory Studies

Routine blood studies may be needed to help rule out noncardiac conditions triggering tachycardia. These may include the following:

  • Complete blood count (CBC)
  • Chemistry panel (blood urea nitrogen [BUN] and creatinine to assess renal status)
  • Liver function tests
  • Thyroid panel

Blood levels of antiarrhythmic medications during therapy and monitoring are typically not helpful for oral medications. Intravenous (IV) lidocaine and procainamide do require serum measurements during treatment. Digoxin is a medication that should typically be avoided in WPW patients because of a preferential decrease in atrioventricular (AV) nodal, rather than pathway, conduction. However, digoxin levels may be helpful if digoxin toxicity is suspected.

Echocardiography

Echocardiography, focusing on cardiac function and dimensions, is needed to evaluate left ventricular (LV) function, septal thickness, and wall motion abnormalities and to help rule out cardiomyopathy and an associated congenital heart defect (CHD), such as hypertrophic cardiomyopathy [HOCM], Ebstein anomaly, or L-transposition of the great vessels. Significantly depressed function may be observed in the setting of an acute dysrhythmia but should typically normalize in the absence of an incessant tachycardia.

Electrocardiography

The diagnosis and management of any cardiac dysrhythmia may first be accomplished by analysis of 12-lead ECG and rhythm strips and their relationship to the clinical setting. Recognizing dysrhythmias on 12-lead ECG findings requires a detailed knowledge of atrial and ventricular activation patterns and deductions related to the mechanisms of atrioventricular (AV) conduction.

Diagnosis of accessory pathways (APs) is indicated. During ventricular pacing, premature ventricular stimulation activates the atria before retrograde depolarization of the His bundle. This indicates that the impulse reached the atria before it depolarized the His bundle and must have traveled via a different pathway (bypass tract).

If the ventricles can be stimulated prematurely during tachycardia at a time when the His bundle is refractory and the impulse still conducts to the atrium (His-refractory or His-synchronous premature ventricular complex [PVC]), this indicates that retrograde propagation traveled to the atrium over a pathway other than the bundle of His, representing the usual inferior input to the AV node.

In addition, if a PVC, delivered at a time when the His bundle is refractory, terminates the tachycardia without retrograde activation of the atria, it most likely invaded, and blocked in, an AP. If repeatable, this is diagnostic of orthodromic reentrant tachycardia (ORT).

The ventriculoatrial (VA) interval (a measurement of conduction over the accessory pathway) is generally constant over a wide range of ventricular-paced rates and coupling intervals of PVCs and during the tachycardia in the absence of aberration. Similar short VA intervals can be observed in some patients during AV nodal reentry, but if the VA conduction time or RP interval is the same during tachycardia and ventricular pacing at comparable rates, an AP is almost certainly present (VA linking).

Tachycardia can be easily initiated after premature ventricular stimulation that conducts in retrograde fashion in the AP but blocks in the AV node or His bundle.

Atria and ventricles are required components of the macroreentrant circuit in ORT or AV reentrant tachycardia (AVRT); therefore, continuation of the tachycardia in the presence of AV or VA block excludes an accessory AV pathway as part of the reentrant circuit.

Characteristic features of WPW syndrome

The classic ECG morphology of WPW syndrome is described as a shortened PR interval (often <120 ms) and a slurring and slow rise of the initial upstroke of the QRS complex (delta wave; see the image below), a widened QRS complex with a total duration greater than 0.12 seconds, and secondary repolarization changes reflected as ST segment–T wave changes that are generally directed opposite the major delta wave and QRS complex. In reality, the ECG morphology varies widely.

12-lead electrocardiogram showing short PR interva 12-lead electrocardiogram showing short PR interval and delta waves consistent with presence of accessory pathway.

Depending on the location of the AP in relation to the sinus node (see below) and the relative transmission characteristics of the AP and the AV node, the morphology of the ECG may vary from a classic presentation, termed manifest preexcitation, to near normal.

In some cases, the electrical impulse’s arrival at the ventricles occurs slightly earlier through the AP (by not undergoing the typical slowing through the AV node), creating preexcitation.

The QRS interval is widened because the ventricles are initially activated via the AP, which lies outside the normal conducting system, producing an early, albeit relatively slow, initial propagation of depolarization forces through the ventricular tissue. This produces the delta wave. The delta wave makes the QRS appear wider than expected and the PR interval somewhat shortened. This is known as a manifest AP because it is easily identifiable on ECG.

WPW syndrome has been described by some as either type A or type B, depending on the appearance of the delta wave/QRS complex in the precordial leads. Type A is described as having an upright positive delta wave in all precordial leads with a resultant R greater than S amplitude in lead V1. Type B has a predominantly negative delta wave and QRS complex in V1 and V2 and becomes positive in transition to the lateral leads, much as in left bundle-branch block (LBBB).

Lown-Ganong-Levine (LGL) syndrome has a shortened PR interval because of the presence of the AP bypassing the AV node, but it has a normal QRS because the AP (James fibers) connects directly with the His bundle and does not depolarize the ventricles directly but depolarizes them via the typical conduction pathway through the His-Purkinje system. The true pathophysiology of this classic description has recently been brought into question.

In other WPW syndrome cases, arrival of the electrical impulse to the ventricle occurs nearly simultaneously through both the accessory pathway and the AV node. When this occurs, preexcitation is absent, and ECG appears normal. Thus, ECG morphology depends directly on the degree of preexcitation (ie, relative conduction speeds).

An AP that does not manifest on ECG is revealed when the rate exceeds the refractory period of the AV node. This has been described as a latent AP. A latent AP can conduct both antegrade and retrograde transmissions.

An AP in which only retrograde transmission of impulses can occur is called a concealed AP and is used only during circus movement tachycardia (CMT or ORT). A concealed AP is not detectable on the regular surface ECG findings, because the ventricle is not preexcited. Tachycardia due to a concealed AP should be considered when the QRS complex is normal and the retrograde P wave occurs well after completion of the QRS complex, out in the ST segment or even in the T wave (long R-P tachycardia).

Although many types of dysrhythmias can occur in a patient with WPW syndrome, ORT and atrial fibrillation (AF) are the most common. ORT is the more common of the two.

A critically timed premature atrial beat that occurs during the refractory period of the AP typically initiates ORT. The impulse, therefore, travels solely down the AV node but returns in a retrograde manner through the AP, resulting in reciprocating tachycardia.

This is a narrow-complex heart rhythm limited by the refractory period of the AV node. The QRS complex is narrow, because the impulses travel in an antegrade manner (orthodromically) through the AV node, and regular, because circus (circular) movement occurs at a regular rate.

Differential diagnosis of this type of WPW dysrhythmia includes paroxysmal supraventricular tachycardia (PSVT). Differentiating between the 2 in an acutely symptomatic patient with a regular-rhythm, narrow-complex tachycardia is difficult. Cardiac dysrhythmias with rates higher than 220 bpm in adults suggest that the dysrhythmia is bypassing the AV node and may reflect an AP or ventricular tachycardia (VT).

Antidromic CMTs are wide and potentially faster because of the relatively short refractory period of most APs. They are termed antidromic because antegrade transmission occurs down the AP from the atria to the ventricles, creating preexcitation of the ventricle adjacent to the AP. These dysrhythmias are regular due to the nature of the circus movement. They are likely to have the classic delta wave appearance of the QRS on the resting ECG.

Differential diagnoses include VT, which also is regular (unless it is torsade de pointes) or PSVT with aberrancy. One should initially consider any regular wide-complex tachycardia to be VT until proven otherwise.

Most cases of regular wide-complex AVRT (AV reentry tachycardia) associated with WPW syndrome that are treated with adenosine consequently are converted to sinus rhythm, though adenosine may induce atrial fibrillation, and DC cardioversion equipment should be available.

AF in patients with WPW syndrome is very common and has an incidence of 11-38%. It is also the deadliest dysrhythmia for these patients because of the possibility of deterioration into ventricular fibrillation (VF).

Another concerning feature of AVRT in patients with WPW is that it can disorganize into AF, which can have disastrous consequences in patients with accessory AV pathways capable of antegrade conduction. Atrial impulses can reach an AP at a rate of 300-400 times per minute and may result in hemodynamic instability due to rapid rates of ventricular response, far in excess of that allowed by the AV node-His-Purkinje axis.[26]

In normal hearts, an individual is protected from exceptionally high ventricular rates by the relatively long refractory period of the AV node. In patients with WPW syndrome, however, the AP often has a much shorter antegrade refractory period, allowing much faster transmission of impulses and correspondingly higher rates (may exceed 300 bpm).

In addition, sympathetic discharge secondary to hypotension may lead to further shortening of the refractory period and subsequent increases in the ventricular rate. If the rate becomes too high, VF may result.

AF through an AP appears as a bizarre, wide-complex, irregular tachycardia on ECG, with rates often in the 250 bpm range or higher. The combination of a rapid rate, a widened QRS complex, and unusual or changing QRS complex morphologies in a young patient strongly suggests the diagnosis.[27]

Localization of accessory pathways

The location of the AP can often be determined through analysis of the spatial direction of the delta wave in the 12-lead ECG by reviewing the maximally preexcited QRS complexes.[28] A general rule is that Q waves (negative delta waves) point away from the earliest site of ventricular activation, which is typically the insertion point of the bypass tract. The most common locations for APs, in decreasing order of frequency, are the left free wall, the posteroseptal and right free wall, and finally the midseptal and anteroseptal regions of the heart.

Several algorithms are available to predict the location of the AP. These algorithms may not be totally accurate because maximal preexcitation is needed, and usually the QRS in WPW pattern is a fusion between AV node and AP depolarization (ie, absent AP depolarization may be present at certain points due to enhanced AV node conduction, although the AP is present), precordial lead placement may vary, as well as chest shape and size and heart shape, size, and location.

A practical concept is that a negative delta wave usually signals the location of the AP, as follows:

  • A negative delta wave in a left-side lead such as I and aVL indicates a left-side AP
  • A negative delta in a right-side lead such as V1 predicts a right-side AP
  • An isoelectric delta in V1 predicts an anteroseptal AP
  • A negative delta in the inferior leads (II, III, and aVF) indicates a posteroseptal AP
  • A positive delta in the inferior leads predicts an anteroseptal AP

A more specific algorithm for location of the AP, based on the polarity of the delta wave or first 40 ms of the QRS, predicts the following AP locations:

  • Left lateral wall - Negative delta waves in lead I and aVL; positive or isoelectric delta waves in II, III, aVF (inferior leads), and V1-4; and negative or isoelectric delta waves in V5-6
  • Left posterior free wall - Positive delta waves in lead I and aVL; negative delta waves in II, III, and aVF; positive delta waves in V1-5; and negative or isoelectric delta wave in V6
  • Posteroseptal - Positive delta waves in lead I and aVL with negative delta waves in II, III, and aVF; isoelectric or positive delta waves in V1; and positive delta waves in the rest of the precordial leads (see the images below)
  • Right free wall - Positive delta waves in I and II, negative delta waves in aVR, isoelectric or negative delta wave in aVF, isoelectric delta wave in V1, isoelectric or positive delta waves in V2-3, and positive delta waves in V4-6
  • Left anteroseptal - Positive delta waves in I, II, and aVF; negative delta wave in aVR; isoelectric or positive delta wave in V1; and positive delta waves in V2-6
  • Right anteroseptal - Positive delta waves in I, II, and aVF; negative delta wave in aVR; negative or isoelectric delta waves in V1-3; and positive delta waves in V4-6
Electrocardiogram of asymptomatic 17-year-old male Electrocardiogram of asymptomatic 17-year-old male who was incidentally discovered to have Wolff-Parkinson-White pattern. It shows sinus rhythm with evident preexcitation. To locate accessory pathway (AP), initial 40 ms of QRS (delta wave) is evaluated. Note that delta wave is positive in I and aVL, negative in III and aVF, isoelectric in V1, and positive in rest of precordial leads. Therefore, this is likely posteroseptal AP.
12-lead electrocardiogram from asymptomatic 7-year 12-lead electrocardiogram from asymptomatic 7-year-old boy with Wolff-Parkinson-White pattern. Delta waves are positive in I and aVL; negative in II, III, and aVF; isoelectric in V1; and positive in rest of precordial leads. This predicts posteroseptal location for accessory pathway.

During orthodromic tachycardia, a narrow complex QRS is evident, with the P wave often detectable as a subtle deflection within the T wave. During antidromic tachycardia, a wide complex QRS is seen and may not be distinguishable from VT (in which case it must be treated as such).

ECG imaging is a recently described noninvasive technique that reconstructs epicardial electrograms from body surface potentials.[29] This modality has been used to identify the exact location of pathways responsible for ventricular preexcitation.[30]

Recording devices

Continuous ECG recordings (eg, via telemetry, 24-hour Holter monitors, event monitors, or implantable loop recorders) are indicated. Continuous monitoring of cardiac rhythm with telemetry can be performed on hospitalized patients in the coronary or progressive care units.

In the outpatient setting, a number of portable recording devices (eg, Holter monitors, event monitors) can be used and should be aimed at symptom-rhythm correlation.

Portable recording systems provide simultaneous two-lead recording that improves the diagnostic yield tremendously. The 2 leads most commonly used for monitoring are II and MCL-I, the latter being similar to V1. These devices have long-term storage capabilities that permit off-line analysis of complex dysrhythmias, even if the physician is not available at the time the rhythm disturbance occurs.

For infrequently occurring dysrhythmias, a number of event recorders are available. They allow the patient to activate the device by pressing a button when an event occurs, providing internal storage and transmission by telephone or wireless communication to a central station for later review.

A small loop recorder can be implanted and can be remotely interrogated for rhythm analysis. This can be used in patients with dysrhythmias that are infrequent or difficult to capture. External loop recorders can be valuable in assessing palpitations after ablation, which are very common and often represent isolated extrasystoles rather than signaling the return of more serious arrhythmias.

In the presence of WPW syndrome without documented SVT and in the presence of symptoms, a transtelephonic transient cardiac event monitor or a longer-term monitoring system may be appropriate.

Stress Testing

Stress testing is an ancillary test and may be used (1) to reproduce a transient paroxysmal SVT (PSVT), which is triggered by exercise, (2) to document the relationship of exercise to the onset of tachycardia, or (3) to evaluate the efficacy of antiarrhythmic drug therapy (class Ic antiarrythmic medications and effects on antegrade preexcitation).

If preexcitation is abruptly lost, stress testing may reveal the refractory periods of APs in patients with WPW syndrome. Such testing may be unreliable, however, because exercise also alters the competing conduction properties of the atrioventricular (AV) node and will favor conduction over the AV node if a septal or left-side AP is present.

Electrophysiologic Study

Esophageal EPS can be used to assess the behavior of the AP, the inducibility of SVT, and the response to drug therapy. This procedure can be performed safely as an outpatient procedure requiring only sedation. Invasive EPS can also be performed for these risk-stratification indications, but this is usually reserved for patients undergoing radiofrequency (RF) ablation.

Intracardiac EPS is performed in a cardiac electrophysiology laboratory. With the use of multipolar catheter electrode systems, recordings from many intracardiac sites can be performed simultaneously, facilitating delineation of the sequence of depolarization and impulse conduction in the atria, AV junction, and ventricle.[4]

Indications

EPS can be used in patients with WPW syndrome to determine the following:

  • The mechanism of the clinical tachycardia
  • The electrophysiologic properties (eg, conduction capability, refractory periods) of the AP and the normal AV nodal and His Purkinje conduction system
  • The number and locations of APs (which are necessary for catheter ablation)
  • The response to pharmacologic or ablation therapy

Features of preexcitation

If a Kent bundle (AV)-type accessory bypass tract conducts in an antegrade fashion, two parallel paths can potentially carry the impulse. The first is the natural one, which comes with inherent physiologic delay over the AV node (decremental conduction). The second is the bypass tract (Kent bundle), which allows the impulse to pass directly without delay from the atrium to the ventricle (nondecremental conduction).

This dual-path mechanism produces a unique QRS complex that is a form of fusion beat. The delta wave results from ventricular activation by the impulse traveling over the AP. The degree of delta (preexcitation) is directly related to the distance of the bypass tract to the sinus node and the speed of conduction over the AV node and His Purkinje system.

The extent to which the wavefront over each route contributes to ventricular depolarization varies, as follows:

  • If delay in AV nodal conduction occurs from either rapid atrial pacing or a premature atrial complex, a greater proportion of the ventricle activates via the bypass tract, and the QRS becomes more preexcited
  • On the other hand, if the bypass tract is far from the sinus node (as in the presence of a left lateral pathway) or if AV nodal conduction is rapid, a larger proportion of the ventricle activates via the normal pathway, and preexcitation will be subtle
  • The normal fusion beat during sinus rhythm has a short or negative His-ventricle (HV) interval; pacing the atrium rapidly at premature intervals accentuates the abnormal ventricular depolarization and further shortens the HV interval
  • Localization of the potential site of pathway for RF ablation may be facilitated by analysis of the delta wave axis as initially described in the classic article by Arruda et al [28]

A negative HV interval during sinus rhythm in the presence of WPW syndrome means that the His deflection occurs after the beginning of the QRS deflection. The more preexcitation, the later the His deflection (ie, more toward the end of the QRS).

This occurs whenever the AP conducts more rapidly than the AV node and the depolarizing wavefront from the AP thus reaches the ventricle before that from the AV node. The earlier that the depolarization from the AP reaches the ventricle with respect to the depolarization from the AV node, the more preexcitation occurs (ie, the wider the QRS and the shorter the RP interval).

During antidromic SVT, a premature atrial extrastimulation that shortens the SVT cycle length with no change in QRS morphology or that terminates SVT with an atrial depolarization (ie, not followed by a QRS) rules out VT. In the first case, the premature atrial depolarization conducts to the ventricles through the AP. In the second case, the premature atrial depolarization reaches the AP’s effective refractory period terminating the SVT in the antegrade limb, also proving that the AP participated in the SVT (ie, it is an AP-mediated SVT and not a VT).

Recognition and localization of accessory pathways

When retrograde atrial activation during tachycardia occurs over an AP that connects the left atrium to the left ventricle, the earliest retrograde activity is recorded from a left atrial electrode (usually positioned in the coronary sinus). This is a left lateral pathway.

When retrograde atrial activation during tachycardia occurs over an AP that connects the right ventricle to the right atrium, the earliest retrograde atrial activity is generally recorded from a lateral right atrial electrode. This is a right ventricular free wall pathway.

Participation of a septal accessory pathway creates earliest retrograde atrial activation in the low-right atrium situated near the septum, anteriorly or posteriorly (depending on the insertion site).

Retrograde atrial activation over the AP can be confirmed by inducing premature ventricular complexes (PVCs) during tachycardia to determine whether retrograde atrial excitation can occur from the ventricle at a time when the His bundle is refractory (His refractory PVCs). Failure to advance the atrium when the His is refractory does not exclude an AP, particularly if far from the pacing site (left lateral pathway).

With entrainment pacing from the right ventricular (RV) apex, orthodromic reentrant tachycardia (ORT) will return with a V-A-V response, typically with a short (<115 ms) postpacing interval (PPI)–tachycardia cycle length (TCL) difference (PPI-TCL) if septal in origin. VA intervals remain fixed during SVT, and AV block cannot occur if the AV AP is critical to the circuit.

Activation mapping using three-dimensional (3D) electroanatomical mapping systems (CARTO, En-Site) may improve pathway localization, particularly when the AP is anteroseptal or midseptal and concern for AV block during RF ablation is present.

Typically, one should ablate on the side being mapped. If mapping the earliest A, ablate in the atrium via transseptal access if necessary). If mapping the earliest V antegrade, perform ablation via a retrograde aortic approach, if on the left side.

Risk assessment and need for ablation

If AF is induced during either an intraesophageal or an EPS, the shortest RR interval between two consecutive preexcited QRSs is measured. If the interval is less than 220 ms, then the risk of sudden death due to VF is believed to be high. Specifically, according to one study, the most discriminating predictor of VF in patients with WPW syndrome was the shortest RR interval during AF of 172 ± 23 ms (vs 230 ± 50 ms).[23] Those patients were considered to be at high risk for developing VF and sudden death should AF occur.

A study of asymptomatic children with WPW pattern who underwent EPS for risk stratification reported that a high proportion of subjects experienced sustained AVRT, AF, or both, with the shortest RR between two consecutive preexcited QRSs being 230-250 ms (mean, 237.5 ± 9.6 ms).[5] The authors concluded that those results may be indicative of the necessity of RF ablation in all asymptomatic individuals with WPW pattern.

Histologic Findings

An extremely detailed postmortem assessment of histology from multiple sections around the AV ring may identify APs. However, this approach is impractical for assessment of every patient with unexplained sudden death.

 

Treatment

Approach Considerations

Treatment of Wolff-Parkinson-White (WPW)-associated arrhythmias is directed at the underlying cause (through the use of radiofrequency [RF] ablation of the accessory pathway [AP], antiarrhythmic drugs in adults to slow AP conduction in certain situations (ie, Mahaim or atriofascicular pathway-mediated supraventricular tachycardia [SVT]; typically, atrioventricular [AV] nodal-conduction blocking medications are avoided in the acute setting of WPW), or AV nodal blocking medications to slow AV nodal conduction).

For adult patients, treatment also addresses the triggers that perpetuate the dysrhythmia, which include coronary heart disease, ischemia, cardiomyopathy, pericarditis, electrolyte disturbances, thyroid disease, and anemia.

Treatment must be individualized for each patient and should include individual risk assessment.[31] Appropriate therapy for WPW syndrome is based on the likely prognosis and on the degree of symptoms the patient experiences. Specific subspecialty consultations are often needed and may include a cardiovascular specialist (adult or pediatric cardiologist) and/or an electrophysiologist (arrhythmia specialist) with expertise in invasive studies.

Despite the importance of risk stratification with electrophysiologic study (EPS) to assess the risk of sudden cardiac death (SCD), few reliable noninvasive markers are known. The adult literature has focused on preexcited RR intervals in atrial fibrillation (AF) as an indicator of the ability to rapidly conduct. In a series of 60 pediatric patients, a preexcited RR interval of less than 220 ms identified patients at high risk for cardiac arrest.[22] Thus, if an AP can conduct 4 impulses per second, it can be considered a high-risk pathway.

Ambulatory monitoring and treadmill testing can provide additional noninvasive information if the preexcitation disappears suddenly at a discrete heart rate. However, care should be exercised in the interpretation of these noninvasive test results. Invasive risk assessment with subsequent RF ablation should be performed in patients who present with syncope or aborted SCD.

The two main treatment approaches to WPW syndrome are (1) pharmacotherapy and (2) EPS with RF catheter ablation. EPS with ablation is the first-line treatment for symptomatic WPW syndrome and for patients with high-risk occupations. It has replaced surgical treatment and most drug treatments. RF ablation used in conjunction with cryoablation for septal APs and APs near small coronary arteries has had high success rates with low risk.[17]  

Drug therapy can be useful in some instances, such as in patients who refuse RF ablation and in temporizing patients with a higher risk of ablation-related complications (eg, AV block with pacing requirement for anteroseptal or midseptal pathways). Medical therapy may also be appropriate in pregnant women until radiation exposure is safe.

In choosing drug therapy, keep in mind that class Ic and class III antiarrhythmic medications will slow AP conduction, facilitating blockage of SVT. If the patient has a history of AF or atrial flutter, an AV nodal blocking medication should also be used.

Initial Management

Patients who present in cardiac arrest or with hemodynamic compromise require management of the ABCs (Airway, Breathing, Circulation), as is standard; this includes having a defibrillator available and providing appropriate monitoring. Once the patient is determined to be experiencing a dysrhythmia, direct-current (DC) cardioversion is indicated.

In a stable patient, various vagal maneuvers may be attempted. A bag of ice slurry to the face is very effective in infants. Older children may be able to perform a Valsalva maneuver. Creative alternatives abound, such as having a patient blow with his thumb in his mouth. Unilateral carotid sinus massage may also be attempted. Ocular compression should not be performed, because it has been associated with retinal injury.

When conservative measures fail, intravenous (IV) access is necessary. Adenosine is the first-line agent and is effective in approximately 90% of reentrant narrow-complex tachycardias. Adenosine must be administered as a rapid bolus because of its short half-life. Most instances of adenosine failure in this setting are caused by inadequate administration of the drug. A defibrillator must be available in the event that new dysrhythmias emerge, particularly postadenosine AF.

Procainamide and esmolol are available for use in resistant cases but should only be administered by physicians familiar with these medications. Verapamil should not be administered to patients younger than 1 year because of risk of severe hypotension, severe bradycardia, or heart failure in this population of patients; this drug has also been reported to accelerate the ventricular rate in AF, leading to rapid conduction that results in ventricular fibrillation (VF).

Pharmacologic Therapy

Antiarrhythmic drugs act on the AV node, myocardial tissue, or the APs. They work by increasing either conduction velocity or the refractory period (prolonging action potential duration) or by prolonging the conduction time through an AP to prevent perpetuation of an AV reciprocating tachycardia. They may also act to reduce the ventricular response to AF or atrial flutter.

Agents acting on atrioventricular node

Verapamil and diltiazem (calcium channel blockers), metoprolol and atenolol (beta-blockers), and digitalis all prolong conduction time and refractoriness in the AV node.

Verapamil and metoprolol do not affect conduction in the AV bypass tract (may slow Mahaim fibers or atriofascicular pathway conduction). IV verapamil can speed up the ventricular response in patients with WPW syndrome who have AF. Verapamil is not recommended as a sole agent in patients with WPW syndrome.

Digitalis shortens refractoriness in the myocardium and in the bypass tract. Thus, it may accelerate the ventricular response in the setting of AF in a patient with WPW syndrome. It should generally be avoided.

Adenosine causes profound changes in AV nodal conduction leading to transient AV block and typically does not affect the accessory pathway conduction. Adenosine should not be used in this setting and could induce VF.

Digoxin is contraindicated in patients with WPW syndrome, although it may play some role in children only. Some deaths from WPW syndrome have been associated with digoxin use.

Agents acting on accessory pathway

Class Ia drugs (eg, quinidine) and class Ic drugs (eg, flecainide, propafenone) slow conduction velocity in the AP and prolong the AP refractory period in the bypass tract.

Amiodarone, dofetilide, and sotalol prolong refractoriness in myocardial tissue, including AV bypass tracts.

Procainamide is no longer available in an oral formulation and is typically only used during EPS or in the emergency department (ED) or cardiac intensive care unit (ICU) setting.

Termination of Acute Episodes

Narrow-complex atrioventricular reentrant tachycardia

Narrow-complex  (AV) reentrant tachycardia (AVRTs) manifests with normal QRS complexes, a ventricular rate higher than 200 bpm, regular RR intervals, and a retrograde P wave well beyond the end of QRS.

It should be treated in the same way as AV nodal reentrant tachycardia (AVNRT), by blocking AV node conduction with (1) vagal maneuvers (eg, Valsalva maneuver, carotid sinus massage, splashing cold water or ice water on the face), (2) IV adenosine 6-12 mg via a large-bore line (the drug has a very short half-life) in adults, or (3) IV verapamil 5-10 mg or diltiazem 10 mg in adults. In pediatric patients, adenosine and verapamil or diltiazem dosing regimens are weight-based.

Both adenosine and calcium channel blockers have been reported to result in atrial fibrillation with rapid, preexcited atrial fibrillation eventuating in ventricular fibrillation; therefore, close monitoring during administration of these agents is essential, and cardioversion equipment and medications must be immediately available. Use of adenosine is preferred due to its short duration of action.

Atrial flutter/fibrillation or wide-complex tachycardia

AF or atrial flutter can be recognized by the presence of abnormal aberrant QRS complexes and irregular RR intervals. In this setting, drugs that prolong the refractory period of the bypass tract should be used, including procainamide (class Ia agent).

If wide-complex tachycardia is present and the diagnosis of ventricular tachycardia (VT) cannot be excluded, the drugs of choice are IV procainamide or amiodarone (in lieu of cardioversion if the patient is stable hemodynamically; see below). Ibutilide may also be useful in this setting (also class III). Lidocaine is not useful for preexcited atrial fibrillation.

Hemodynamically unstable tachycardia and electrical cardioversion

In patients with a very fast ventricular rate, hemodynamic instability (eg, hypotension, mental status change) may ensue. The initial treatment of choice in such patients is DC synchronized electrical cardioversion, biphasic. The electrical shock depolarizes all excitable myocardium, lengthens refractoriness, interrupts reentrant circuits, discharges foci, and establishes electrical homogeneity that terminates reentry.

Because myocardial damage may occur with increases in applied energy, the minimum effective energy should be used and the energy should be titrated. A level of 100 J (monophasic or lower biphasic) successfully terminates most supraventricular tachycardias (SVTs) and should be tried initially. If that fails, a second shock with higher energy (200 J or 360 J) may be delivered.

Cardioversion can have several adverse effects. It may induce dysrhythmias because of inadequate synchronization, with the shock occurring during the ST segment or T wave. Rarely, even a properly synchronized shock can produce VF. Postcardioversion dysrhythmias are generally transient and do not require treatment.

Embolic episodes may occur in 1-3% of the patients converted from AF to sinus rhythm if the episodes are longer than 48 hours. In those patients, anticoagulation must be addressed prior to cardioversion, with consideration of a transesophageal echocardiogram to exclude left atrial thrombus.

Further measures

Patients with WPW syndrome who are admitted to the hospital after initiation of medical treatment in the ED may require further evaluation and management as follows:

  • Continuous telemetry monitoring to look for resurgence of tachyarrhythmia and the degree of control of the ventricular rate in those with atrial fibrillation
  • Initiation, dose adjustment, and maintenance of long-term antiarrhythmic drugs for preventing recurrences (However, patients generally undergo RF ablation.)
  • Laboratory evaluation and correction of electrolyte and metabolic abnormalities that may have acted as triggers
  • Carefully monitor for proarrhythmias, especially when quinidine, amiodarone, dofetilide, or sotalol are initiated.

A few days of inpatient telemetry monitoring, including determination of QT interval lengthening on electrocardiographic (ECG) readings, is required for some of these agents. An increase in the QT interval of 25% to longer than 500 ms or 550 ms with a bundle-branch block should be avoided.

Transfer

Certain patients with WPW syndrome must be transferred to a tertiary facility for comprehensive evaluation and management by a cardiac electrophysiologist, which may include EPS or ablative therapy. Such patients include those presenting with any of the following:

  • SCD
  • Syncope
  • Significant symptomatic tachyarrhythmias
  • Uncertain diagnosis (in those with wide-complex tachycardia)
  • Associated structural heart disease (eg, Ebstein anomaly, cardiomyopathy, mitral valve prolapsed)
  • A family history of SCD
  • No symptoms, but are working in professions in which spontaneous occurrence of tachyarrhythmia may jeopardize public safety, cause much mental anguish, or influence insurability
  • AF or atrial flutter

Ideally, if transfer of patients with WPW syndrome and other causes of SVT is indicated, they undergo conversion of their rhythm in the referring institution and are transferred in sinus rhythm.

Radiofrequency Ablation

In RF ablation, platinum-tipped 3.5- to 8-mm steerable multielectrode catheters are advanced via the femoral artery or vein to locate and ablate the AP by delivering thermal RF energy. APs at all the sites in the heart and in persons of all age groups can be ablated successfully. In addition, RF ablation of the AP in patients with frequent AP-mediated tachycardia improved left ventricular systolic and diastolic functions.[32]

EPS with RF ablation is now the treatment of choice for most adults and many children with symptomatic WPW syndrome, as well as many asymptomatic patients. This approach has largely supplanted surgical and DC modalities because it is more efficacious, safe, and cost-effective.[33] With successful EPS and RF ablation, patients are usually cured of the disease and are not at risk for further tachyarrhythmias related to the AP. Note that RF ablation with fluoroscopy includes increased radiation exposure.[17]  Fluoroscopic-free imaging modalities (eg, three-dimensional electroanatomic mapping, ultrasonography) reduce radiation exposure, but they have not yet supplanted fluoroscopy.[17]

Although current guidelines do not always recommend routine EPS in patients with asymptomatic WPW syndrome, especially in children who are younger than 12 years,[5] others strongly advocate the need for at least an intraesophageal study to assess the risk for SCD.[34]

Patients with Ebstein anomaly should be evaluated for multiple APs. During EPS and RF ablation, all such pathways should be recognized and treated.

Patients presenting with tachyarrhythmic symptoms who do not opt for RF ablation may require drug therapy to prevent further episodes. (See the section on Long-Term Antiarrhythmic Therapy.)

Indications

RF ablation is indicated in the following patients:

  • Patients with symptomatic atrioventricular  reentrant tachycardia (AVRT)
  • Patients with AF or other atrial tachyarrhythmias that have rapid ventricular response via an AP (preexcited AF)
  • Patients with AVRT or AF with rapid ventricular rates found incidentally during EPS for unrelated dysrhythmia, if the shortest preexcited RR interval during AF is less than 250 ms
  • Asymptomatic patients with ventricular preexcitation whose livelihood, profession, insurability, or mental well-being may be influenced by unpredictable tachyarrhythmias or in whom such tachyarrhythmias would endanger the public safety [5]
  • Patients with WPW and a family history of SCD

Asymptomatic patients who have a low-risk pathway and no SVT can be monitored expectantly, or they may undergo RF ablation to prevent any possibilities of SCD and prevent late onset of SVT.[16] In addition, there is an associated rise in incidence of atrial fibrillation in patients with WPW which may be reduced with prophylactic RF ablation of the accessory pathway.

Symptomatic individuals with orthodromic tachycardia should undergo risk assessment and should be offered therapy according to their symptoms. RF ablation can be curative and carried out with a high degree of success, a low complication rate, and a low recurrence rate. Symptomatic individuals with antidromic tachycardia (ie, antegrade conduction through the AP) should be offered ablation.

Identification of accessory pathway and selection of ablation site

First, perform EPS (1) to determine that the AP is part of the tachycardia reentrant circuit and (2) to locate the optimal site for ablation. APs may be located in the left or right free wall or septum of the heart. In approximately 5-10% of patients, multiple pathways are present.

The ventricular insertion site is indicated by the earliest onset of the ventricular electrogram in relation to the delta wave during sinus rhythm or atrial pacing. The atrial insertion site is indicated by the region of the shortest VA interval during orthodromic tachycardia (ie, AVRT) or ventricular pacing. Mechanical trauma during mapping, “bump mapping”, often may occur at the site of pathway insertion and signals a potential effective ablation site.

During EPS, direct recordings of the AP potential indicate the optimal site for ablation, followed by areas of AV or VA fusion. Successful ablation sites show stable fluoroscopic and electrical features. During orthodromic AVRT, the time between the ventricular and atrial potentials is short and an AP potential may be observed.

Tip temperatures of at least 50°C are required for permanent elimination of AP conduction. Often, a single, well-placed RF lesion will cure the patient (see the image below). The RF ablation creates a conduction block that can be seen on intracardiac electrography (ie, during EPS) between the atrial activation and the AP potential.

Accessory pathway potential and local AV fusion at Accessory pathway potential and local AV fusion at successful RF ablation site with loss of preexcitation and return of normal HV interval.

Effectiveness and safety

Success rates for RF catheter ablation exceed 90%. Anteroseptal or midseptal pathways have lower success rates due to difficulty achieving a safe lesion formation near the AV node and His bundle. In experienced operators’ hands, the success rate should still exceed 90%, but may come with a 5-10% rate of AV block, usually leading to permanent pacemaker implantation.

Posteroseptal pathways are expected to have a more than 90% success rate as well, with little risk of injury to the AV node in experienced hands. Occasionally, during ablation of the slow pathway of the AV node for AVNRT, a right posteroseptal pathway may also be ablated, as they are typically in close proximity.

RF catheter ablation is relatively safe, with a complication rate of approximately 1% in most centers. A three-catheter ablation technique  appears to be similarly sucessful and safe as, but involves less cost than, the standard five-catheter approach for mapping and ablation of SVTs in pediatric patients with WPW and left-side AP.[35] Adverse consequences include bleeding complications, pericardial effusion, chest pain, stroke, myocardial infarction, and AV node block.

Surgical Care

Surgical open-heart procedures were more common before RF ablation was developed. Now, RF catheter ablation has virtually eliminated surgical open heart treatments in the vast majority of patients, with the following exceptions:

  • Patients in whom RF catheter ablation (with repeated attempts) fails [12]
  • Patients undergoing concomitant cardiac surgery (eg, for structural heart disease [12] ) (possible exception)
  • Patients with other tachycardias with multiple foci who require surgical intervention (very rare)

The 2012 Heart Rhythm Society (HRS)/European Heart Rhythm Association (EHRA)/European Cardiac Arrhythmia Society (ECAS) (HRS/EHRA/ECAS) expert consensus statement on catheter and surgical ablation of atrial fibrillation noted that implantable implantable cardioverter-defibrillator (ICD) therapy is not indicated for VF or VT that is amenable to surgical or catheter ablation—such as atrial arrhythmias associated with the WPW syndrome.[3]

Long-Term Antiarrhythmic Therapy

Long-term oral medication is the mainstay of therapy in patients not undergoing RF ablation. Response to long-term antiarrhythmic therapy for the prevention of further episodes of tachycardia in patients with WPW syndrome remains quite variable and unpredictable. Some drugs may paradoxically make the reciprocating tachycardia more frequent.

Class Ic drugs (eg, flecainide, propafenone) are typically used with an AV nodal blocking agent in low doses to avoid atrial flutter with a 1:1 conduction. class III drugs (eg, amiodarone, sotalol) are also reasonable choices, although these agents are less effective for altering accessory pathway conduction properties. Class Ic drugs should not be given if the patient has structural heart disease (coronary artery disease, myocardial infarction, congestive heart failure, left ventricular hypertrophy). Class Ic drugs are typically used with an AV nodal blocking agent.

The best long-term plan is to not use drugs at all. All patients who have symptomatic WPW syndrome should be referred for electrophysiologic studies (EPS) and considered for ablation, which has a very high cure rate and a low complication rate. Patients who have asymptomatic APs with short refractory periods (<240 ms) are poor candidates for medical therapy and are best treated with ablation as well.

In pregnancy, the safest options for antiarrhythmic therapy are sotalol, which has a class B rating, and flecainide, which has a class C rating but has been safely used in many patients.

Diet

Most patients presenting with WPW syndrome are not elderly. Patients presenting with structural heart disease, cardiomyopathy, or heart failure may require a low-salt, low-cholesterol diet.

Activity

Generally, no activity restrictions are recommended in patients with ECG findings of preexcitation in the absence of tachycardia. These individuals should be restricted from high-risk professions (eg, airline pilot) and may be restricted from competitive sports. Note that the 2012 Pediatric and Congenital Electrophysiology Society (PACES) and the Heart Rhythm Society (HRS) recommended referral to a pediatric electrophysiology specialist for asymptomatic adolescents with WPW and ventricular preexcitation, regardless of their athletic status.[17]

Patients presenting with tachycardias and accessory pathways should avoid participating in competitive sports, because catecholamines can decrease the refractoriness of the bypass tract and facilitate tachyarrhythmias. Patients with hypertrophic cardiomyopathy, or the Ebstein anomaly should also abstain from competitive sports.

Once a curative procedure (eg, RF ablation of the accessory pathway) has been successfully performed, most patients can return to competitive sports or to high-risk occupations several months later. Generally, if patients have to alter their lifestyles significantly because of the disease, they probably are not receiving appropriate current therapy.

Prevention

WPW syndrome is largely congenital or hereditary. No particular method exists to eliminate the possibility of developing APs. In the future, genetic recognition and counseling may become a useful tool. Screening of school-aged children or athletes through preparticipation evaluation has been suggested but, so far, has not been considered cost-effective.

Long-Term Monitoring

Patients with WPW syndrome need to continue antiarrhythmic therapy as prescribed. If symptoms related to tachyarrhythmias recur, patients should inform their physicians.

Arrange follow-up visits to assess for the recurrence of dysrhythmia, the effectiveness of antiarrhythmic therapy, and adverse effects of medications. Follow-up ECG or Holter monitoring may be needed to assess for changes in QT duration and the recurrence of dysrhythmias or proarrhythmias. Patients who take amiodarone require careful periodic monitoring for adverse effects and organ toxicity, including thyroid function tests, ophthalmic examination, pulmonary function tests, and hepatic function tests.

Patients who undergo EPS with RF ablation may require monitoring of wound care after hospital discharge. Further follow-up care to assess for the recurrence of dysrhythmia is also needed.

Patients with underlying structural heart disease (eg, Ebstein anomaly) may require follow-up care by a specialist in adult congenital heart disease.

If a patient with WPW syndrome dies suddenly, siblings and first-degree relatives should be screened for preexcitation.

Routine EPS is not recommended after RF ablation when its only purpose to ensure that the ablation was curative; however, EPS may be performed if the patient becomes symptomatic or has documented SVT.

Asymptomatic patients with only the ECG findings of preexcitation should be seen at frequent intervals and should consider prophylactic RF ablation; recent studies show a significant drop in dysrhythmia onset after RF ablation (5% vs 60% in a control group).[8]

Children with symptomatic WPW syndrome who undergo RF ablation sustain myocardial damage or injury. Lesion size at a successful site is typically only 3-5 mm. How this damaged myocardium will change as children grow is still not known.

 

Guidelines

Guidelines Summary

2012 PACES/HRS guidelines (Wolff-Parkinson-White)

The 2012 Pediatric and Congenital Electrophysiology Society (PACES)/Heart Rhythm Society (HRS) guidelines indicate that more invasive EPS should be considered when the absolute loss of manifest preexcitation cannot be clearly demonstrated. The recommendations include the following[17] :

  • Measurement of the shortest preexcited RR interval during induced atrial fibrillation (AF)
  • Determination of the number and location of accessory pathways (APs)
  • Evaluation of the anterograde and retrograde features of the APs and atrioventricular (AV) node
  • Assessment at multiple cycle lengths of the effective efractory period of the APs and the ventricle

For the evaluation of asymptomatic patients aged 8-21 years with WPW, the guidelines recommend an exercise stress test when ambulatory ECGs show persistent excitation.[17]  If noninvasive testing does not clearly show abrupt loss of preexcitation, clinicians should consider using invasive risk stratification (transesophageal/intracardiac) to assess the shortest preexcite RR interval in AF.[17]

The guidelines include the following management recommendations in asymptomatic patients aged 8-21 years with WPW[17] :

  • For those with a shortest preexcited RR interval (SPERRI) of 250 ms or less in AF, consider catheter ablation and factor in the associated procedural risk factors on the basis of the AP anatomic site.
  • Consider catheter ablation also for those with concomitant (1) structural heart disease, regardless of the anterograde AP features, or (2) ventricular dysfunction due to dyssynchronous contractions, regardless of the anterograde bypass tract characteristics.
  • Previously asymptomatic patients who develop cardiovascular (CV) symptoms should be considered symptomatic and thus potential candidates for catheter ablation.
  • For those with a SPERRI longer than 250 ms in AF, consider deferring catheter ablation.
  • Consider administration of attention-deficit/hyperactivity disorder (ADHD) medications; if ADHD medications are used, closely monitor patients for CV symptoms.

2014 AHA/ACC/HRS guidelines (Atrial Fibrillation)

The 2014 American Heart Association (AHA)/American College of Cardiology (ACC)/HRS guidelines management of atrial fibrillation (AF) include the following specific recommendations for WPW and preexcitation syndromes[36] : 

Class I (Level of evidence: C)

  • Patients with AF, WPW syndrome, and rapid ventricular response who are hemodynamically compromised should receive prompt direct-current cardioversion. (Level of evidence: C)
  • For patients with preexcited AF and rapid ventricular response who are not hemodynamically compromised, administer IV procainamide or ibutilide to restore sinus rhythm or slow the ventricular rate. (Level of evidence: C)
  • Catheter ablation of the accessory pathway in symptomatic patients with preexcited AF, especially if the accessory pathway has a short refractory period that allows rapid antegrade conduction.

Class III:(Level of evidence: B)

  • Administration of intravenous amiodarone, adenosine, digoxin (oral or intravenous), or nondihydropyridine calcium channel antagonists (oral or intravenous) in patients with WPW syndrome who have preexcited AF is potentially harmful because these drugs accelerate the ventricular rate.

2015 ACC/AHA/HRS guidelines (supraventricular tachycardia)

In 2015, joint ACC/AHA/HRS guidelines for the management of supraventricular tachycardia (SVT) were released that included specific recommendations for both acure and ongoing managment of AV reentry tachycardia (AVRT).[37]

Vagal maneuvers and/or IV adenosine are the recommended initial treatments for acute AVRT. (Class I; Level of evidence B-R)

Additional recommendations for acute treatment when adenosine and vagal maneuvers are ineffective or contraindicated are summarized below.

Hemodynamically unstable patients

  • Synchronized cardioversion (class I; level of evidence, B-NR)

Hemodynamically stable patients

  • IV beta blockers, diltiazem, or verapamil (class IIa; level of evidence, B-R for patients without preexcitation on their resting ECG during sinus rhythm; and class IIb; level of evidence, B-R for patients with preexcitation on their resting ECG during sinus rhythm)
  • Synchronized cardioversion when beta blockers, diltiazem, or verapamil are ineffective or contraindicated (class I; level of evidence, B-NR)

The guidelines note that for rhythms that break or recur spontaneously, synchronized cardioversion is not appropriate.

IV digoxin or amiodarone and intravenous or oral beta blockers, diltiazem, and verapamil are potentially harmful for treatment in patients with pre-excited atrial fibrillation (class III; level of evidence, C-LD).

For management of ongoing orthodromic AVRT, the guidelines recommend catheter ablation of the accessory pathway.(class I; level of evidence,  B-R) Patients with preexcitation resting ECG who are not candidates or prefer not to undergo catheter ablation have the following alternative treatment options:

  • Flecainide or propafenone in patients without structural heart disease or ischemic heart disease (class IIa; Level of evidence B-R)
  • Sotalol or dofetilide (class IIb; level of evidence, B-R)
  • Oral beta blockers, diltiazem, verapamil (class IIb; level of evidence,  C-LD)
  • Oral amiodaronewhen other therapies are ineffective or contraindicated (class IIb; level of evidence, C-LD)
  • Oral digoxin is potentially harmful for ongoing management in patients with AVRT or AF and preexcitation on their resting ECG (class III; level of evidence, C-LD)

2015 ESC guidelines (Ventricular Arrhythmias and Prevention of Sudden Cardiac Death

In its 2015 guidelines for management of venticular arrhythmias and prevention of sudden cardiac death, the European Society of Cardiology (ESC) recommends ablation is in WPW patients resuscitated from sudden cardiac arrest due to AF and rapid conduction over the accessory pathway causing VF. (class I; level of evidence, B). Additionally, ablation should be considered in patients who are symptomatic and/or who have accessory pathways with refractory periods ≤240 ms in duration. (class IIb; level of evidence,  B)[38]

2014 PACES/HRS guidelines (Arrhythmias in Adult Congenital Heart Disease)

The 2014 PACES/HRS guidelines for managment of arrhythmias in adult congenital heart disease (CHD) recommend preoperative EPS for the identification and mapping of arrhythmias that may be managed with surgical ablation or incisional lesion sets in patients with[12] : 

  • History of unexplained syncope or sustained ventricular tachycardia that is not due to a correctable predisposing etiology;
  • Documented SVT, not including AF;
  • Ventricular preexcitation.

 A preoperative electrophysiology study may be considered in adults with CHD and any of the following criteria:

  • Nonsustained rapid atrial or ventricular tachyarrhythmias
  • Moderate or complex CHD known to be at high risk for atrial arrhythmia development but without documented sustained arrhythmia
  • History of palpitations or symptoms thought to be related to arrhythmia
  • Atrial fibrillation triggering supraventricular arrhythmia 

Preoperative EPS is not recommended in adults with CHD and the following criteria:

  • Simple forms of CHD, no history of palpitations or arrhythmia symptoms, and no significant documented arrhythmia
  • AF without a triggering supraventricular arrhythmia.
 

Medication

Medication Summary

Emergency treatment in Wolff-Parkinson-White (WPW) patients with hemodynamic instability is directed toward converting the rhythm to sinus through a brief episode of atrioventricular (AV) block. Adenosine is the drug of choice for immediate conversion of narrow-complex supraventricular tachycardia (SVT) but should not be used for preexcited atrial fibrillation (AF). Esmolol has also been used with some success.

Beta-blockers are probably the medications most commonly used to treat SVT in the presence of preexcitation. They are moderately effective and have frequent, but rarely life-threatening, adverse effects (except in the presence of reactive airway disease). Their efficacy in reducing the risk of accelerated conduction of AF in WPW patients is unclear. More potent medications (eg, flecainide, propafenone, sotalol, or amiodarone) may have more effect on accessory pathway (AP) conduction or refractoriness than beta-blockers and are preferred by some.

The use of digoxin or verapamil for long-term therapy appears to be contraindicated for many patients with WPW syndrome, because these medications may enhance antegrade conduction through the AP by increasing the refractory period in the AV node. In addition, digoxin may shorten the refractory period of the AP, further enhancing its antegrade conduction.

Antiarrhythmic Agents

Class Summary

Antiarrhythmic agents alter the electrophysiologic mechanisms responsible for dysrhythmia, prolonging the refractory period of the conduction tissue, the AP, or both.

Adenosine (Adenocard, Adenoscan)

Adenosine slows conduction time through the AV node. It can interrupt atrioventricular reentrant tachycardia (AVRT) by blocking conduction in the AV node to restore normal sinus rhythm in paroxysmal supraventricular tachycardia (PSVT), including PSVT associated with WPW syndrome. It should not be given to patients with preexcitation unless by a cardiac electrophysiologist.

Verapamil (Verelan, Calan)

Verapamil interrupts reentry at the AV node and restores normal sinus rhythm in patients with PSVT. It is used for short-term treatment only in children older than 2 years. It is not intended for long-term treatment, because of a shortened refractory period. Do not use it in children younger than 2 years, because of severe hypotension.

Digoxin (Lanoxin)

Digoxin has direct inotropic effects in addition to indirect effects on the cardiovascular system. However, it may shorten the refractory period. Most deaths in WPW have been associated with digoxin use.

Procainamide

Procainamide is a class Ia antiarrhythmic. It increases the refractory period of atria, ventricles, and APs. It is excellent in preexcited AF or atrial flutter.

Quinidine

Quinidine maintains normal heart rhythm and converts AF or atrial flutter. It is not recommended as a first-line drug for WPW syndrome.

Amiodarone (Cordarone, Pacerone)

Amiodarone may inhibit AV conduction and sinus node function. It prolongs the action potential and refractory period in myocardium and inhibits adrenergic stimulation.

Sotalol (Betapace, Sorine)

Sotalol is a class III antiarrhythmic agent that blocks potassium channels, prolongs action potential duration, and lengthens the QT interval. It is a noncardiac selective beta-adrenergic blocker.

Diltiazem (Cardizem, Dilacor, Cartia XT, Tiazac)

Diltiazem slows AV nodal conduction.

Ibutilide (Corvert)

Ibutilide is a class III antiarrhythmic agent that may work by increasing action potential duration, thereby changing atrial cycle length variability. Mean time to conversion is 30 minutes. Two thirds of patients who converted were in sinus rhythm at 24 hours. Ventricular arrhythmias occurred in 9.6% of patients and were mostly premature ventricular complexes (PVCs). The incidence of torsades de pointes was less than 2%.

Dofetilide (Tikosyn)

Dofetilide increases monophasic action potential duration, primarily through delayed repolarization. It terminates induced reentrant tachyarrhythmias (eg, AF, atrial flutter, ventricular tachycardia [VT]) and prevents their reinduction. No data are available on its use in WPW syndrome.

Flecainide (Tambocor)

Flecainide blocks sodium channels, producing dose-related decreases in intracardiac conduction in all parts of heart. It has its greatest effect on the His-Purkinje system (HV conduction). Effects on AV nodal conduction time and intra-atrial conduction times, though present, are less pronounced than those on ventricular conduction velocity.

Flecainide is indicated for the treatment of paroxysmal AF or atrial flutter associated with disabling symptoms and PSVT, including AV nodal reentrant tachycardia (AVNRT), AVRT, and other SVTs of unspecified mechanism associated with disabling symptoms in patients without structural heart disease. It is also indicated for prevention of documented life-threatening ventricular arrhythmias, such as sustained VT. It is not recommended in less severe ventricular arrhythmias, even if patients are symptomatic.

Propafenone (Rythmol)

Propafenone shortens the upstroke velocity (phase 0) of a monophasic action potential. It reduces the fast inward current carried by sodium ions in Purkinje fibers and, to a lesser extent, myocardial fibers. It may increase the diastolic excitability threshold and prolong the effective refractory period (ERP). It reduces spontaneous automaticity and depresses triggered activity.

Propafenone is indicated for treatment of documented life-threatening ventricular arrhythmias, such as sustained VT. It appears to be effective in the treatment of SVTs, including AF and atrial flutter. It is not recommended in patients with less severe ventricular arrhythmias, even if they are symptomatic.

Esmolol (Brevibloc)

Esmolol is an ultra–short-acting agent that selectively blocks beta1-receptors, with little or no effect on beta2-receptor types. It is excellent for patients at risk of complications from beta-blockade, particularly those with reactive airway disease, mild-to-moderate left ventricular dysfunction, and/or peripheral vascular disease. Its short half-life of 8 minutes allows for titration to desired effect and quick discontinuation if needed.

Propranolol (Inderal LA, InnoPran XL)

Propranolol is a class II antiarrhythmic nonselective beta-adrenergic receptor blocker with membrane-stabilizing activity that decreases automaticity of contractions.

Atenolol (Tenormin)

Atenolol selectively blocks beta1-receptors with little or no effect on beta2 types.

 

Questions & Answers

Overview

What is Wolff-Parkinson-White (WPW) syndrome?

What are the clinical manifestations of Wolff-Parkinson-White (WPW) syndrome?

What are the signs and symptoms of Wolff-Parkinson-White (WPW) syndrome in infants?

What are the signs and symptoms of Wolff-Parkinson-White (WPW) syndrome in a verbal child?

What are the signs and symptoms of Wolff-Parkinson-White (WPW) syndrome in older patients?

Which physical findings are characteristic of Wolff-Parkinson-White (WPW) syndrome?

Which cardiac defects may be present in Wolff-Parkinson-White (WPW) syndrome?

What is the role of lab studies in the evaluation of Wolff-Parkinson-White (WPW) syndrome?

What is the role of electrocardiogram (ECG) in the diagnosis of Wolff-Parkinson-White (WPW) syndrome?

What is the role of echocardiography in the diagnosis of Wolff-Parkinson-White (WPW) syndrome?

What is the role of stress testing in the diagnosis of Wolff-Parkinson-White (WPW) syndrome?

What is the role of electrophysiologic studies (EPS) in the diagnosis of Wolff-Parkinson-White (WPW) syndrome?

What are the treatment options for Wolff-Parkinson-White (WPW) syndrome associated with arrhythmias?

How are tachycardias treated in Wolff-Parkinson-White (WPW) syndrome?

What are the treatments for atrial flutter/fibrillation in Wolff-Parkinson-White (WPW) syndrome?

What is the initial treatment of hemodynamically unstable tachycardia in Wolff-Parkinson-White (WPW) syndrome?

When is radiofrequency (RF) ablation indicated for the treatment of Wolff-Parkinson-White (WPW) syndrome?

When is surgical open heart treatment indicated in Wolff-Parkinson-White (WPW) syndrome?

What are the medications used in the treatment of Wolff-Parkinson-White (WPW) syndrome?

How is preexcitation in Wolff-Parkinson-White (WPW) syndrome defined?

What is Wolff-Parkinson-White (WPW) syndrome?

What is the current definition for Wolff-Parkinson-White (WPW) syndrome?

What are the classic electrocardiogram (ECG) findings associated with Wolff-Parkinson-White (WPW) syndrome?

What are the increased cardiac risks for patients with Wolff-Parkinson-White (WPW) syndrome?

What is the significance of a concealed bypass tract in patients with Wolff-Parkinson-White (WPW) syndrome?

What is the risk of sudden cardiac death in patient with Wolff-Parkinson-White (WPW) syndrome?

What is the pathophysiology of Wolff-Parkinson-White (WPW) syndrome?

What is the role of accessory pathways in the pathogenesis of Wolff-Parkinson-White (WPW) syndrome?

How is the degree of preexcitation on a surface electrocardiogram (ECG) estimated in Wolff-Parkinson-White (WPW) syndrome?

What are the types of supraventricular tachycardia (SVT) in Wolff-Parkinson-White (WPW) syndrome?

What is the role of orthodromic tachycardia in the pathogenesis of Wolff-Parkinson-White (WPW) syndrome?

How is the orthodromic tachycardia characterized on ECG in Wolff-Parkinson-White (WPW) syndrome?

What is the role of concealed accessory pathways in the pathogenesis of Wolff-Parkinson-White (WPW) syndrome?

How is orthodromic tachycardia differentiated from AV nodal reentrant tachycardia (AVNRT) in Wolff-Parkinson-White (WPW) syndrome?

What is antidromic tachycardia in Wolff-Parkinson-White (WPW) syndrome?

How is antidromic tachycardia characterized on ECG in Wolff-Parkinson-White (WPW) syndrome?

What is the prevalence of antidromic and orthodromic tachycardia in Wolff-Parkinson-White (WPW) syndrome?

What causes of Wolff-Parkinson-White (WPW) syndrome?

What is the role of genetics in the etiology of Wolff-Parkinson-White (WPW) syndrome?

What is the familial form of Wolff-Parkinson-White (WPW) syndrome?

What is the association between Wolff-Parkinson-White (WPW) syndrome and autosomal dominant familial hypertrophic cardiomyopathy?

How does infantile Pompe disease cause Wolff-Parkinson-White (WPW) syndrome?

What is the role of MYH6 variants in the etiology of Wolff-Parkinson-White (WPW) syndrome?

What is the role of lysosome-associated membrane protein 2 (LAMP2) in the etiology of Wolff-Parkinson-White (WPW) syndrome?

What is the role of the Ebstein anomaly in the etiology of Wolff-Parkinson-White (WPW) syndrome?

What is the role of preexcitation in the etiology of Wolff-Parkinson-White (WPW) syndrome?

What is the prevalence of ventricular preexcitation in the US?

What is the incidence of Wolff-Parkinson-White (WPW) syndrome in the US?

What is the incidence of tachycardia in patients with Wolff-Parkinson-White (WPW) syndrome in the US?

What are the most common accessory pathways involved in Wolff-Parkinson-White (WPW) syndrome in the US?

What is the prevalence of reciprocating tachycardia in Wolff-Parkinson-White (WPW) syndrome?

What is the global incidence and prevalence of Wolff-Parkinson-White (WPW) syndrome?

How does the prevalence of Wolff-Parkinson-White (WPW) syndrome vary by age?

How does the prevalence of Wolff-Parkinson-White (WPW) syndrome vary by sex?

What are the racial predilections of Wolff-Parkinson-White (WPW) syndrome?

What is the prognosis of Wolff-Parkinson-White (WPW) syndrome?

What is the prognosis of Wolff-Parkinson-White (WPW) syndrome in asymptomatic patients with only preexcitation on ECG?

What is the incidence of sudden cardiac death (SCD) in patients with Wolff-Parkinson-White (WPW) syndrome?

What are risk factors for sudden cardiac death (SCD) in Wolff-Parkinson-White (WPW) syndrome?

What is the cause of sudden cardiac death (SCD) in Wolff-Parkinson-White (WPW) syndrome?

What are the death rates for Wolff-Parkinson-White (WPW) syndrome?

What are the risks factors atrial fibrillation (AF) in patients with Wolff-Parkinson-White (WPW) syndrome?

What are the risk factors for ventricular fibrillation (VF) in Wolff-Parkinson-White (WPW) syndrome?

What are the morbidities associated with Wolff-Parkinson-White (WPW) syndrome?

What are the complications of Wolff-Parkinson-White (WPW) syndrome?

What is the importance of patient education for Wolff-Parkinson-White (WPW) syndrome?

What do patients with Wolff-Parkinson-White (WPW) syndrome need to carry with them?

What information about their treatment should patients with Wolff-Parkinson-White (WPW) syndrome be given?

Presentation

What is the presentation of Wolff-Parkinson-White (WPW) syndrome?

What are the signs and symptoms of Wolff-Parkinson-White (WPW) syndrome in infants?

What are the signs and symptoms of Wolff-Parkinson-White (WPW) syndrome in children?

What are the signs and symptoms of Wolff-Parkinson-White (WPW) syndrome?

Which tachycardias most commonly produce symptoms in Wolff-Parkinson-White (WPW) syndrome?

What is the clinical progression of supraventricular tachycardia (SVT) in Wolff-Parkinson-White (WPW) syndrome?

What are the symptoms of paroxysmal supraventricular tachycardia (PSVT) in Wolff-Parkinson-White (WPW) syndrome?

What causes syncope in Wolff-Parkinson-White (WPW) syndrome?

What causes polyuria in Wolff-Parkinson-White (WPW) syndrome?

Which cardiac exam findings are characteristic of Wolff-Parkinson-White (WPW) syndrome?

What are the physical findings characteristic of Wolff-Parkinson-White (WPW) syndrome in children?

What are the physical findings characteristic of supraventricular tachycardia (SVT) in Wolff-Parkinson-White (WPW) syndrome?

What are the physical findings characteristic of supraventricular tachycardia (SVT) in infants with Wolff-Parkinson-White (WPW) syndrome?

Which cardiac defects may be present in Wolff-Parkinson-White (WPW) syndrome?

When do findings of congenital heart defects (CHDs) or cardiomyopathy become apparent in Wolff-Parkinson-White (WPW) syndrome?

What is the incidence of congenital heart disease (CHD) in Wolff-Parkinson-White (WPW) syndrome?

What is the incidence of Ebstein anomaly in Wolff-Parkinson-White (WPW) syndrome?

What are the physical findings of glycogen-storage diseases in Wolff-Parkinson-White (WPW) syndrome?

What are congenital heart diseases (CHDs) associated with Wolff-Parkinson-White (WPW) syndrome?

What is the appearance of abnormal QRS complexes in Wolff-Parkinson-White (WPW) syndrome?

DDX

What are the clinical manifestations of Wolff-Parkinson-White (WPW) syndrome?

What is the most common mechanism of Wolff-Parkinson-White (WPW) syndrome in children?

How is an automatic mechanism differentiated from reentry in Wolff-Parkinson-White (WPW) syndrome?

How is a regular tachycardia differentiated from Wolff-Parkinson-White (WPW) syndrome?

Which conditions with paroxysms of supraventricular tachycardia (SVT) need to be differentiated from Wolff-Parkinson-White (WPW) syndrome?

What are Mahaim fibers?

What are the electrocardiogram (ECG) findings if Mahaim fibers are present?

How do atriofascicular tracts help differentiate Wolff-Parkinson-White (WPW) syndrome from preexcited tachycardia caused by Mahaim fibers?

What are the diagnostic considerations for Wolff-Parkinson-White (WPW) syndrome in the presence of left free wall bypass tract atrioventricular (AV) reentrant tachycardia (AVRT)?

Which electrocardiogram result rules out Mahaim fibers in the differential diagnosis of Wolff-Parkinson-White (WPW) syndrome?

How is Lown-Ganong-Levine (LGL) syndrome differentiated from Wolff-Parkinson-White (WPW) syndrome?

How are entities that involve wide-QRS supraventricular tachycardia (SVT) distinguished in the differential diagnosis of Wolff-Parkinson-White (WPW) syndrome?

How are nodoventricular or fasciculoventricular tracts differentiated from Wolff-Parkinson-White (WPW) syndrome?

Which tachycardias are associated with Wolff-Parkinson-White (WPW) syndrome when the accessory pathway (AP) is just a bystander?

What are the clinical presentations of Wolff-Parkinson-White (WPW) syndrome in patients with atrial fibrillation (AF)?

What causes sudden cardiac death in Wolff-Parkinson-White (WPW) syndrome with AF?

Which patients with Wolff-Parkinson-White (WPW) syndrome have a long accessory pathway (AP) refractory period?

How does intermittent preexcitation affect the disease course of Wolff-Parkinson-White (WPW) syndrome in children?

What are the differential diagnoses for Wolff-Parkinson-White Syndrome?

Workup

What determines the extent of workup for suspected Wolff-Parkinson-White (WPW) syndrome?

What is the role of lab testing in the diagnosis of Wolff-Parkinson-White (WPW) syndrome?

How is Wolff-Parkinson-White (WPW) syndrome diagnosed?

What should be included in the evaluation of Wolff-Parkinson-White (WPW) syndrome?

Which blood studies are used to rule out noncardiac causes of tachycardia in the evaluation of Wolff-Parkinson-White (WPW) syndrome?

What is the role of blood serum measurement of medications in the management of Wolff-Parkinson-White (WPW) syndrome?

What is the role of echocardiography in the diagnosis of Wolff-Parkinson-White (WPW) syndrome?

How are cardiac dysrhythmias diagnosed and managed in Wolff-Parkinson-White (WPW) syndrome?

How are accessory pathways (APs) diagnosed in Wolff-Parkinson-White (WPW) syndrome?

What is the role of ventriculoatrial (VA) interval in the diagnosis of Wolff-Parkinson-White (WPW) syndrome?

How is tachycardia initiated in Wolff-Parkinson-White (WPW) syndrome?

Which ECG finding excludes an accessory AV pathway as part of the reentrant circuit in Wolff-Parkinson-White (WPW) syndrome?

What are the characteristic features of Wolff-Parkinson-White (WPW) syndrome on ECG?

How might the morphology of the electrocardiogram (ECG) for Wolff-Parkinson-White (WPW) syndrome vary?

What is characteristic of the electrical impulses on ECG in Wolff-Parkinson-White (WPW) syndrome?

Why does the QRS interval widen in Wolff-Parkinson-White (WPW) syndrome?

What are type A and B Wolff-Parkinson-White (WPW) syndrome?

How is Lown-Ganong-Levine (LGL) syndrome differentiated from Wolff-Parkinson-White (WPW) syndrome on ECG?

When does an ECG appear normal in Wolff-Parkinson-White (WPW) syndrome?

What is latent AP in Wolff-Parkinson-White (WPW) syndrome?

Which findings on ECG suggest a concealed AP in Wolff-Parkinson-White (WPW) syndrome?

What are the most common dysrhythmias in Wolff-Parkinson-White (WPW) syndrome?

Which findings on ECG suggest ORT in Wolff-Parkinson-White (WPW) syndrome?

How is paroxysmal supraventricular tachycardia (PSVT) differentiated from ORT in Wolff-Parkinson-White (WPW) syndrome dysrhythmia?

Which finding on ECG suggests antidromic circus movement tachycardias (CMTs) in Wolff-Parkinson-White (WPW) syndrome?

What are possible outcomes of atrioventricular reentrant tachycardia (AVRT) in Wolff-Parkinson-White (WPW) syndrome treated with adenosine?

What is the prevalence of atrial fibrillation (AF) in Wolff-Parkinson-White (WPW) syndrome?

What are possible complications of atrioventricular reentrant tachycardia (AVRT) in Wolff-Parkinson-White (WPW) syndrome?

What are ventricular rates in Wolff-Parkinson-White (WPW) syndrome?

Which ECG findings suggest sympathetic discharge due to hypotension in Wolff-Parkinson-White (WPW) syndrome?

Which ECG finding suggests AF through an AP in Wolff-Parkinson-White (WPW) syndrome?

How is the location of an accessory pathway (AP) identified in Wolff-Parkinson-White (WPW) syndrome?

What are the limitations of algorithms to predict the location of the AP in Wolff-Parkinson-White (WPW) syndrome?

How are negative delta waves used to locate the AP in Wolff-Parkinson-White (WPW) syndrome?

What is the algorithm for location of AP in Wolff-Parkinson-White (WPW) syndrome based on the polarity of the delta wave?

Which ECG findings suggest orthodromic tachycardia in Wolff-Parkinson-White (WPW) syndrome?

What is the role of ECG in the diagnosis of Wolff-Parkinson-White (WPW) syndrome?

When is continuous ECG recording indicated in the management of Wolff-Parkinson-White (WPW) syndrome?

What is the role of portable ECG recording devices in the diagnosis of Wolff-Parkinson-White (WPW) syndrome?

What is the role of event recorders in the diagnosis and management of Wolff-Parkinson-White (WPW) syndrome?

What is the role of small loop recorders in the diagnosis of Wolff-Parkinson-White (WPW) syndrome?

When is a transtelephonic transient cardiac event monitor used in the diagnosis of Wolff-Parkinson-White (WPW) syndrome?

What is the role of stress testing in the diagnosis of Wolff-Parkinson-White (WPW) syndrome?

What are the limitations of stress testing in the diagnosis of Wolff-Parkinson-White (WPW) syndrome?

What is the role of esophageal electrophysiologic study (EPS) in the diagnosis of Wolff-Parkinson-White (WPW) syndrome?

What is the role of intracardiac electrophysiologic study (EPS) in the diagnosis of Wolff-Parkinson-White (WPW) syndrome?

What are the indications for electrophysiologic study (EPS) in the diagnosis of Wolff-Parkinson-White (WPW) syndrome?

Which findings on EPS suggest preexcitation in Wolff-Parkinson-White (WPW) syndrome?

What are the variations for ventricular depolarization in Wolff-Parkinson-White (WPW) syndrome?

Which factors increase preexcitation in Wolff-Parkinson-White (WPW) syndrome?

What are the features of preexcitation during antidromic SVT in Wolff-Parkinson-White (WPW) syndrome?

What is the left lateral pathway in EPS of Wolff-Parkinson-White (WPW) syndrome?

What is the right ventricular free wall pathway in EPS of Wolff-Parkinson-White (WPW) syndrome?

How does a septal accessory pathway appear on EPS in Wolff-Parkinson-White (WPW) syndrome?

How is retrograde atrial activation over the AP in Wolff-Parkinson-White (WPW) syndrome confirmed on EPS?

What is the significance of entrainment pacing on EPS in Wolff-Parkinson-White (WPW) syndrome?

What is the role of activation mapping in the diagnosis of Wolff-Parkinson-White (WPW) syndrome?

Which findings on EPS increase the risk of sudden cardiac death in patients with Wolff-Parkinson-White (WPW) syndrome?

Which finding on EPS is an indication for RF ablation in asymptomatic individuals with Wolff-Parkinson-White (WPW) syndrome?

What are the histologic findings characteristic of sudden cardiac death in Wolff-Parkinson-White (WPW) syndrome?

Treatment

What are the treatment options for Wolff-Parkinson-White (WPW) syndrome?

Which triggers for Wolff-Parkinson-White (WPW) syndrome should be treated in adults?

Why should treatment be individualized for each patient with Wolff-Parkinson-White (WPW) syndrome?

Which noninvasive markers are used for risk stratification in Wolff-Parkinson-White (WPW) syndrome?

How is ambulatory monitoring and treadmill testing used in the management of Wolff-Parkinson-White (WPW) syndrome?

What are the main treatment approaches to Wolff-Parkinson-White (WPW) syndrome?

When is drug therapy indicated for Wolff-Parkinson-White (WPW) syndrome?

What needs to be considered drug selection to treat Wolff-Parkinson-White (WPW) syndrome?

What is the initial treatment for cardiac arrest with hemodynamic compromise in Wolff-Parkinson-White (WPW) syndrome?

Which vagal maneuvers are attempted in the initial treatment for cardiac arrest with hemodynamic compromise in Wolff-Parkinson-White (WPW) syndrome?

When is IV adenosine indicated in the treatment of cardiac arrest with hemodynamic compromise Wolff-Parkinson-White (WPW) syndrome?

What is the role of procainamide and esmolol in the treatment of Wolff-Parkinson-White (WPW) syndrome?

What is the role of antiarrhythmic drugs in the treatment of Wolff-Parkinson-White (WPW) syndrome?

Which drugs act on the atrioventricular (AV) node in the treatment of Wolff-Parkinson-White (WPW) syndrome?

Which drugs act on the accessory pathway (AP) in the treatment of Wolff-Parkinson-White (WPW) syndrome?

What are the manifestations of narrow-complex atrioventricular (AV) reentrant tachycardia (AVRT) in Wolff-Parkinson-White (WPW) syndrome?

How is narrow-complex atrioventricular (AV) reentrant tachycardia (AVRT) treated in Wolff-Parkinson-White (WPW) syndrome?

How is atrial fibrillation (AF) or atrial flutter identified in Wolff-Parkinson-White (WPW) syndrome?

How is atrial fibrillation (AF) treated in Wolff-Parkinson-White (WPW) syndrome?

How is hemodynamic instability treated in Wolff-Parkinson-White (WPW) syndrome?

Which energy level is effective for termination of most supraventricular tachycardias (SVTs) in Wolff-Parkinson-White (WPW) syndrome?

What are the adverse effects of cardioversion in Wolff-Parkinson-White (WPW) syndrome?

What is the incidence of embolic episodes in Wolff-Parkinson-White (WPW) syndrome and how are they treated?

What is included in the inpatient evaluation and management of Wolff-Parkinson-White (WPW) syndrome?

When is the transfer to a tertiary facility for comprehensive evaluation and management indicated in Wolff-Parkinson-White (WPW) syndrome?

What is the role of radiofrequency (RF) ablation in the treatment of Wolff-Parkinson-White (WPW) syndrome?

Why is EPS with RF ablation the treatment of choice for symptomatic and asymptomatic Wolff-Parkinson-White (WPW) syndrome?

What are the recommendations for routine electrophysiologic studies (EPS) in asymptomatic Wolff-Parkinson-White (WPW) syndrome?

How is radiofrequency (RF) ablation used to treat Ebstein anomaly in Wolff-Parkinson-White (WPW) syndrome?

What is the alternative treatment to RF ablation for tachyarrhythmic symptoms in Wolff-Parkinson-White (WPW) syndrome?

What are the indications for RF ablation in Wolff-Parkinson-White (WPW) syndrome?

What are the benefits of prophylactic RF ablation in asymptomatic Wolff-Parkinson-White (WPW) syndrome?

How is orthodromic tachycardia treated in Wolff-Parkinson-White (WPW) syndrome?

How is the AP identified and ablation site selected in the treatment of Wolff-Parkinson-White (WPW) syndrome?

What is the success rate for RF ablation in the treatment of Wolff-Parkinson-White (WPW) syndrome?

What is the safety of RF ablation in the treatment of Wolff-Parkinson-White (WPW) syndrome?

What is the role of surgical open heart procedures in the treatment of Wolff-Parkinson-White (WPW) syndrome?

How is Wolff-Parkinson-White (WPW) syndrome treated in patients who do not undergo RF ablation?

Which drugs are used to treat Wolff-Parkinson-White (WPW) syndrome?

What is the best long-term treatment plan for Wolff-Parkinson-White (WPW) syndrome?

How is Wolff-Parkinson-White (WPW) syndrome treated during pregnancy?

Which diet restrictions may be beneficial in Wolff-Parkinson-White (WPW) syndrome?

What are the activity restrictions in patients with Wolff-Parkinson-White (WPW) syndrome?

When should competitive sports be avoided by patients with Wolff-Parkinson-White (WPW) syndrome?

When can patients with Wolff-Parkinson-White (WPW) syndrome return to competitive sports?

How is Wolff-Parkinson-White (WPW) syndrome prevented?

What is the duration of antiarrhythmic therapy for Wolff-Parkinson-White (WPW) syndrome?

What is included in follow-up visits for Wolff-Parkinson-White (WPW) syndrome?

What is included in the treatment of Wolff-Parkinson-White (WPW) syndrome following electrophysiologic studies (EPS) and radiofrequency (RF)?

What follow-up care is needed for underlying structural heart disease in Wolff-Parkinson-White (WPW) syndrome?

Who should be screened for preexcitation following a sudden death from Wolff-Parkinson-White (WPW) syndrome?

When is routine electrophysiologic study (EPS) contraindicated in the management of Wolff-Parkinson-White (WPW) syndrome?

What is included in the follow-up of asymptomatic patients with Wolff-Parkinson-White (WPW) syndrome?

What myocardial damage is caused by RF ablation in children with Wolff-Parkinson-White (WPW) syndrome?

Guidelines

What are the PACES/HRS guidelines for electrophysiologic study (EPS) in Wolff-Parkinson-White (WPW) syndrome?

What are the PACES/HRS guidelines for the evaluation and diagnosis of Wolff-Parkinson-White (WPW) syndrome?

What are the PACES/HRS treatment guidelines for asymptomatic Wolff-Parkinson-White (WPW) syndrome in patients aged 8-21 years old?

What are the AHA/ACC/HRS treatment guidelines for atrial fibrillation (AF) in Wolff-Parkinson-White (WPW) syndrome?

What are the AHA/ACC/HRS treatment guidelines for supraventricular tachycardia (SVT) in Wolff-Parkinson-White (WPW) syndrome?

What are the AHA/ACC/HRS guidelines for the acute management of supraventricular tachycardia (SVT) in Wolff-Parkinson-White (WPW) syndrome?

When is synchronized cardioversion contraindicated in the treatment of Wolff-Parkinson-White (WPW) syndrome?

Which drugs are contraindicated in the treatment of hemodynamically stable patients with Wolff-Parkinson-White (WPW) syndrome?

What are the AHA/ACC/HRS treatment guidelines for orthodromic atrioventricular reentrant tachycardia (AVRT) in Wolff-Parkinson-White (WPW) syndrome?

What are the ESC treatment guidelines for Wolff-Parkinson-White (WPW) syndrome?

What are the PACES/HRS treatment guidelines for adult congenital heart disease (CHD) in Wolff-Parkinson-White (WPW) syndrome?

What are the PACES/HRS recommendations for preoperative EPS in adults with congenital heart disease (CHD) and Wolff-Parkinson-White (WPW) syndrome?

In which patients with CHD do the PACES/HRS guidelines recommend against preoperative EPS for Wolff-Parkinson-White (WPW) syndrome?

Medications

What are the goals of emergency treatment of hemodynamic instability in Wolff-Parkinson-White (WPW) syndrome?

What is the role of beta-blockers in the treatment of Wolff-Parkinson-White (WPW) syndrome?

What is the role of digoxin and verapamil in the treatment of Wolff-Parkinson-White (WPW) syndrome?

Which medications in the drug class Antiarrhythmic Agents are used in the treatment of Wolff-Parkinson-White Syndrome?