Wolff-Parkinson-White Syndrome Treatment & Management

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.

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).

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.

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.

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 successful RF ablation site with loss of preexcitation and return of normal HV interval.

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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 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 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.

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.

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.

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.

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.