eMedicine Specialties > Pediatrics: Cardiac Disease and Critical Care Medicine > Cardiology

Ventricular Tachycardia

Mark E Alexander, MD, Assistant Professor, Department of Pediatrics, Children's Hospital of Boston and Harvard Medical School
Charles I Berul, MD, Associate Professor of Pediatrics, Harvard Medical School; Senior Associate, Department of Cardiology, Children's Hospital of Boston

Updated: Feb 3, 2009

Introduction

Background

Ventricular arrhythmia (VA) may be an isolated and completely benign finding in children, a marker of serious systemic disease or myopathy, or a mechanism for sudden cardiac death (SCD) and syncope.

Isolated premature ventricular contractions (PVCs) are reasonably common. They occur with low daily frequency in as many as 40% of patients with apparently normal hearts.^1,2,3,4 PVCs occur with increased frequency in more than 60% of patients with some types of repaired congenital heart disease (CHD). By comparison, sustained VA is much less frequent. Although sustained VA can occur in apparently normal hearts, approximately 50% of patients have either CHD or myopathy. An increasingly sophisticated molecular understanding of the role of electrical myopathies, including ion-channel defects such as long QT syndrome (LQTS), offers increased insight into the nature of some of these diseases.

Clinical choices regarding imaging and therapy primarily focus on the potential mortality risks associated with the specific clinical setting. The incidence of SCD in pediatric patients is low. Even among patients with known heart disease, consider the potential risks of potent antiarrhythmic medications and of nonpharmacologic therapy (eg, catheter ablation, implantable antitachycardia pacemakers and/or defibrillators). Even with the low incidence of sudden death in pediatric patients, clinical decisions are often difficult.

Pathophysiology

Reentrant, automatic, or triggered mechanisms may cause VA, just as these mechanisms cause supraventricular tachycardia (SVT) and other arrhythmias. Each of these mechanisms can occur in structurally and functionally normal hearts. Both myopericarditis and many forms of cardiomyopathy increase the potential for VAs. Myocardial tumors result in mechanical stresses that facilitate arrhythmias.

Reentrant arrhythmia

Reentrant arrhythmia depends on a circuit, often caused by surgical scar, fibrosis, or fatty degeneration. These areas of functionally abnormal tissue foster the conditions necessary for reentry. These conditions permit a zone of slow conduction, a line of functional unidirectional block, and a circuit that allows circus rhythm to continue. Pediatric patients with surgical ventricular scars, such as those with postoperative ventricular tachycardia (VT) after repair of tetralogy of Fallot, are commonly cited examples of this mechanism. Chaotic rhythms (eg, ventricular fibrillation) are also examples of reentry mechanisms. In clinical practice, reentrant rhythms are triggered by premature beats, and the tachycardia is often terminated with direct-current (DC) cardioversion. An abrupt onset and a generally stable rate are other characteristics of reentrant rhythms.

Automatic rhythms

Automatic rhythms are more common than reentrant rhythms in pediatric patients with apparently normal hearts and are caused by abnormal cellular automaticity. The most frequent automatic rhythm is caused by increased spontaneous depolarization of phase 4 of the cardiac action potential. Abnormal automaticity, in turn, may be the result of metabolic derangement, or the automaticity may be idiopathic. Metabolic derangements that may result in abnormal automaticity include hypokalemia, hypomagnesemia, and local cellular abnormalities that may include inflammation from myocarditis. High atrial rates suppress, but do not eliminate, automatic VT. These rates vary with the autonomic state, often in complicated fashions. A benign accelerated idioventricular rhythm is an example of an autonomic mechanism.

At a cellular level, ion-channel defects, such as LQTS, allow abnormal cellular automaticity to trigger potentially fatal polymorphic VT, also known as torsade de pointes. Triggered arrhythmia may also play a role in poisoning by antiarrhythmic drugs (eg, digoxin).

Frequency

United States

The frequency of VA entirely depends on the underlying substrate.

Large pediatric referral centers may encounter 3-5 patients with sustained VT each year.⁵  The incidence of low-grade ectopy is notably increased in patients with CHD or cardiac myopathies. Among patients with CHD, this incidence is concentrated among those who have had ventricular incisions (eg, ventricular septal defects, D-transposition with ventricular septal defects, tetralogy of Fallot) and aortic stenosis; as many as two thirds of patients in this population have some ectopy. This incidence appears to be increased in older patients, probably among those undergoing repair relatively late in life and with techniques used before the mid 1980s.

Although individual underlying myopathies are rare, each contributes to the overall incidence of VA. Hypertrophic cardiomyopathy (HCM) is most common, with a frequency as high as 0.02-0.2% of the population, although the population-based frequency among young people is generally lower.⁶ Ion-channel defects (eg, LQTS) are less common; the frequency is difficult to quantitate but is probably approximately 1 case per 5000-10,000 persons. Despite the rarity of these conditions, each has an annual mortality risk as high as 3-5%.

International

The etiology of VA varies internationally. Chagas disease (trypanosomiasis) is an epidemic cause of dilated cardiomyopathy in Brazil and in other regions of South America.

In Europe, a heritable arrhythmogenic right ventricular dysplasia (ARVD) may be a leading cause of sudden death and VT in young people, particularly younger adults. The difference in perceived frequency likely results from a combination of genetic factors, variable definitions of ARVD, and differences in regional recognition of this entity.

Mortality/Morbidity

The overwhelming majority of pediatric patients evaluated for nonsustained VA have no symptoms or nonspecific palpitations. Obvious concerns include risk of cardiac syncope or SCD. This risk is low, except in selected patients with organic heart disease, for whom the annual risk of sudden death may be as high as 3% for those with sustained VT. The frequency distribution of sudden death in CHD overlaps with that of ventricular ectopy (see Media file 1).

Much concern regarding VA focuses on identifying preventable causes of SCD. The annual incidence of SCD in most clinically defined subgroups of pediatric patients is low. Nonselected pediatric populations have exceptionally low mortality rates (approximately 1-5 deaths per 100,000 patient-years). In contrast, the annual sudden death rate in the general adult population is 1-3 deaths per 1000 patient-years; the annual mortality rate in adult survivors of myocardial infarction with depressed ventricular function and inducible, nonsuppressible VT is 20%. For older patients with palliated heart disease or genetic arrhythmias, the risks are higher, although the rate is still usually no more than 1-3% annually. Issues of predicting low-frequency disease—difficult issues in any setting—are magnified in the population with CHD and particularly in the overall pediatric population.

Among infants and children with minimal symptoms and normal ventricular function (and even very frequent VA, including VT), most have spontaneous resolution of their arrhythmia, with little intercurrent morbidity.^7,8,9,10,11

Race

Data about the influence of race in pediatric SCD are limited. Incidences of some heritable myopathies vary by ethnic group. Despite these variations, most diagnoses should be considered in all ethnic groups. The incidence of LQTS appears to be decreased in blacks, and ARVD appears most frequent in patients of southern European ancestry. Although Brugada syndrome has been identified in many ethnic groups, it is identical to the sudden unexpected nocturnal death syndrome identified in men of Southeast Asian ancestry.

Sex

No significant sex differences have been reported in overall incidence or severity of VA, though patterns of distribution of different LQTS genotypes may vary by sex. In addition, the implications of LQTS, HCM, ARVD, and other genetic cardiac defects appear to have some sex specificity.

Age

Population-based studies in children have been relatively small but demonstrated a biphasic peak of simple ventricular ectopy in apparently healthy infants. This rate decreases during preschool and elementary school ages and increases with adolescence. As patients move into adult life, the incidence of ventricular ectopy continues to steadily increase (see Media file 2). Although as many as 15% of infants and 40% of adolescents have infrequent ventricular ectopy, high-grade ectopy and VT are notably infrequent.

The incidence of VA is somewhat bimodal in patients without structural heart disease. Infants and adolescents have more cases of VA than do toddlers and younger school-aged children. The nature and classification of these cases also differs with age.

In patients with repaired CHD, incidence of VA is notably increased among older adolescents and young adults. This increase may reflect the management approach taken when these patients were younger, the long period after open-heart repair, and/or the influence of autonomic changes on the heart during adolescence.

Clinical

History

• The following historical details raise particular concern for ventricular arrhythmia (VA):
  • Presence and severity of symptoms
  • Presence of symptoms with exercise
  • Previous cardiac diagnoses and procedures
  • Family medical history suggestive of inherited disease
  • Potential for recent medication or recreational drug use
• In the pediatric population, neurally mediated syncope is so common—and life-threatening arrhythmia is so rare—that investigations of VA in patients with syncope are often unrevealing. Details of the history and family history can direct additional, extensive investigation. Diagnostic findings such as "class II" genetic mutations, which may represent pathologic findings, or nonreproducible findings during intracardiac studies may represent false-positives.
  • A family history of sudden death before age 40 years should raise suspicions, even if the cause was an apparent accident.
  • Numerous familial low-incidence cardiomyopathies have arrhythmia as an important symptom. These cardiomyopathies are characterized by several phenotypes and variable penetrance.
  • When a potentially genetic disorder is identified, careful family investigation can identify other affected families members. The reported yields vary but may approach 50%.  
• Precipitating events may include the following:
  • Cocaine or other recreational drug use
  • Tricyclic antidepressant (TCA) use and overdose
  • Antiarrhythmia medications
  • Other agents that affect repolarization: Several Web sites offer useful references about these drugs.
    • Sudden Arrhythmia Death Syndromes (SADS) Foundation
    • Arizona Center for Education and Research on Therapeutics (CERT)
    • The initial 1998 American Heart Association (AHA) Scientific Statement, Cardiovascular Monitoring of Children and Adolescents Receiving Psychotropic Drugs
    • Newer documents that include a comprehensive review of pediatric arrhythmia risks and suggest a more controversial screening practice, including Cardiovascular Monitoring of Children and Adolescents With Heart Disease Receiving Medications for Attention Deficit/Hyperactivity Disorder
  • Potential for skeletal myopathy
  • Recent surgical procedures
  • Central lines (eg, direct mechanical ectopy)
  • Recent illnesses (eg, potential for myocarditis): Fever may be a potent trigger for VA associated with Brugada syndrome.  
• Syncope
  • Apparent cardiac syncope consistently increases the potential of identifying a life-threatening disease that requires active management.
  • Cardiac syncope, in contrast to typical neurally mediated syncope, is characterized by abrupt onset associated with exercise, clinically significant injury, incontinence, seizure, and rapid recovery when arrhythmia is transient.
  • Palpitations are common in neurally mediated syncope and in cardiac syncope. During benign episodes, these palpitations are often described as hard beats at lower rates, compared with the rapid pulse identified when tachycardia triggers syncope.
  • Syncope in the presence of known or apparent heart disease should be presumed to represent a potentially serious arrhythmia until proven otherwise.
  • A new presentation of syncope and VAs may be particularly worrisome.
• Near-syncope or dizziness
  • The vast majority of patients with episodic dizziness, light-headedness, or other presyncopal symptoms have benign or self-limited diagnoses.
  • Clinical correlation is critical when presyncopal symptoms are associated with ventricular ectopy or other arrhythmia.
• Palpitations
  • Patients with isolated premature ventricular contractions (PVCs) and those with sustained arrhythmia may report symptomatic palpitations. Particularly with PVCs, the postextrasystolic beat may have an increased stroke volume.
  • Of note, many patients do not report any symptoms and cannot identify when they are having ventricular beats. As in patients with syncope, palpitations frequently occur in patients without significant arrhythmia. Ambulatory ECGs (eg, those recorded with Holter or memory-looping event monitors) are critical tools to correlate symptoms and rhythm.
• Chest pain
  • Most chest pain is clearly of musculoskeletal origin (costochondritis); physical examination reveals reproducible point tenderness and no clinical suggestion of heart disease.
  • Another common scenario is atypical chest pain, which is described as brief, sharp, and stabbing. This finding is poorly correlated with exercise and not correlated with the ECG.
  • Chest pain may represent a marker of hypertrophic cardiomyopathy (HCM) or relatively common diagnoses.
  • Typical angina is extremely rare.
  • Sudden cardiac death (SCD) and rare cases of coronary artery disease are clearly related in some way. VA may be secondary to Kawasaki disease, congenital coronary anomalies, or typical angina.
  • Pediatric chest pain, is typically poorly defined and may include arrhythmia symptoms, pulmonary symptoms or GI symptoms in addition to anxiety. In contrast to older adults, the serious cardiac causes of chest pain are all rare, which influences both the need for additional testing and the yield of that testing.

Physical

• Cardiac examination
  • Perform detailed cardiac examination. Focus on clinically apparent arrhythmia and physical signs of heart failure or structural heart disease.
  • Normal results do not exclude serious or life-threatening disease.
• General physical examination: Particularly focus on evidence of occult or apparent skeletal myopathy, neurocutaneous syndromes, rickets, and previous procedures.

Causes

Potential causes of VAs include the following:

• Mechanical causes
  • Intraventricular catheters
  • Myocardial tumors
• Metabolic causes
  • Hypokalemia
  • Hyperkalemia
  • Hypocalcemia
  • Acidemia
  • Hypoxia
  • Fever
  • Hypomagnesemia
• Drugs
  • Digoxin toxicity
  • Proarrhythmia
  • Most antiarrhythmia drugs (especially classes I-A, I-C, III)
  • Positive inotropes and chronotropes (eg dopamine, isoproterenol).
  • Other drug toxicity
  • Anesthesia
• Inflammatory causes
  • Viral carditis
  • Other myocarditis
• Cardiomyopathy - Muscular dystrophy
• Genetic causes
• Electrical myopathy
  • Long QT
  • Brugada syndrome
  • Catecholaminergic polymorphic ventricular tachycardia (VT)
• Structural - Congenital heart disease (CHD)
• Neoplastic causes - Tumors (eg, rhabdomyoma)
• Sustained and nonsustained VT
  • Sustained VT is defined as consecutive ventricular rhythm longer than 30 seconds at rates faster than 110-120 beats per minute (bpm) or a comparable arrhythmia requiring urgent cardioversion.
  • Nonsustained VT includes 3 or more consecutive beats lasting less than 30 seconds. High-grade ventricular ectopy is the VA classification that includes combinations of ventricular couplets and polyform PVCs, which are more frequent than isolated PVCs and less sustained than VT.
• Nonstructural heart disease
  • Electrical myopathies, LQTS: This familial ion-channel defect is caused by a microdeletion; deletions in chromosomes 3, 4, 7, 11, and 21 have been identified. Although each defect is unique, they share a tendency to abnormal repolarization and an increased risk of sudden death associated with torsade de points. High-dose beta-blockade has been a mainstay therapy for years. Novel approaches with atrial pacing, implantable cardioverter/defibrillators (ICDs), and gene-specific ion-channel manipulation may help certain patients.
  • Arrhythmogenic right ventricular cardiomyopathy (ARVC): This is the most frequent diagnosis in southern Europeans who die during exercise. This complex and heterogeneous myopathy is associated with fatty degeneration of the right ventricle and inducible VA.
  • HCM: SCD, apparently mediated by VT, occurs in young people with HCM. High-grade ectopy, as shown on Holter monitoring, is an apparent risk factor for SCD in adults with HCM; however, this finding provides little assistance to pediatric patients. Correlation in genotype-positive families with HCM suggests that as many as a quarter of children and adolescents with mild or early forms of HCM may be missed during ECG screening.¹² Arrhythmia and mortality risks associated with HCM widely vary. Data from population-based pediatric studies and the pediatric cardiomyopathy registry suggest that the risk for older children and adolescents with HCM is 1% per year or less.⁶ Infants and those with inborn errors of metabolism represent patients with notably increased risk.
  • Brugada syndrome: Brugada syndrome represents another identifiable genetic defect (of the sodium channel) that causes VAs. Patients with this syndrome tend to present with a pattern of right bundle-branch block (RBBB) on resting ECG and ST-segment elevation. Both fevers and full stomachs may be important triggers of the pattern, and fever is a frequent contributor to childhood events.¹³
  • Catecholaminergic polymorphic VT: This is yet another identifiable ion-channel defect that occurs on a relatively frequent familial basis, with recurrent polymorphic VT, a normal resting ECG, and normal repolarization. Genetic studies have identified patients and families with mutations in the ryanodine receptor, among other gene defects. These patients often have atrial and junctional arrhythmias along with relative sinus bradycardia.
• Acute myocarditis
  • Acute viral myocarditis with depressed ventricular function and active inflammation, whatever the etiology, can cause ventricular ectopy and VT.
  • Short-term drug therapy to suppress arrhythmia is indicated while myocarditis is managed.
  • For the acute patient with profound ventricular dysfunction urgent transfer for consideration of mechanical support may be life-saving.  
  • Arrhythmias may persist well after the hemodynamic dysfunction has resolved.
• Occult or focal myocarditis
  • Although infrequent, well-documented cases of focal or occult myocarditis associated with VA have clearly occurred.
  • Some patients with frequent ectopy or idiopathic VT may also have subclinical myocarditis. Functional imaging studies and endomyocardial biopsy may help identify these patients.
• Idiopathic arrhythmias
  • Idiopathic arrhythmias have characteristic patterns but lack the diagnoses outlined above.
  • Benign arrhythmia is always diagnosed with caution on the basis of the symptoms, family history, echocardiogram, response to and rate of exercise, morphology, and persistence of the arrhythmia.
    • Isolated PVCs: Infrequent, isolated PVCs, particularly with a trigger such as anesthesia or an intracardiac catheter, require little investigation. PVCs notably more frequent than expected for the patient's age may warrant investigation to seek evidence of sustained arrhythmia.
    • Right ventricular outflow tract VT: Frequently asymptomatic, this type has a left bundle-branch block (LBBB) morphology, often-repetitive salvos of VT, possibly subtle MRI findings, and low-to-absent mortality. ARVD is often a difficult diagnostic challenge.
    • RBBB VT: This type may be automatic. Some occurrences may be reentrant VT triggered by atrial pacing or atrial premature beats. Seen in all ages, RBBB VTs often respond to verapamil therapy.
    • Accelerated idioventricular rhythm: Typically seen in infants and young children, accelerated idioventricular rhythm rates are slightly faster than sinus beats. LBBB is usually seen, suggesting a right ventricular focus. No mortality has been reported with this condition, and therapy is infrequently needed. Carefully observe affected infants for evidence of increasing VT or decreasing function.
• Congenital heart disease
  • PVCs: These are seen in as many as two thirds of adolescents and young adults with moderate-to-severe valvar aortic stenosis or repaired tetralogy of Fallot. PVCs are also seen in some patients with ventricular septal defects and in patients with irreparable heart disease, especially those with pulmonary hypertension. Without symptoms, these findings are best interpreted by understanding the hemodynamics of the underlying illness.
  • Nonsustained and sustained VT
    • The classifications of nonsustained and sustained VT in patients with CHD are identical to those of patients with structurally normal hearts. These classifications should be considered in the context of the patient's symptoms and current hemodynamic status.
    • The presence of clinical VT and, in some settings, VT induced during electrophysiologic testing, may be independent of other hemodynamic defects in predicting the risk of cardiac arrest and mortality. Careful consultation and evaluation is appropriate. Tetralogy of Fallot, the defect most commonly associated with spontaneous or induced monomorphic VT, is strongly associated with increasing age, increasing age at initial repair, and residual hemodynamic defects. Management choices are complex and may include drug therapy, implantable cardioverters/defibrillator (ICD) therapy, ablation, or management of residual hemodynamic issues.

Differential Diagnoses

Other Problems to Be Considered

Premature ventricular beats
Ventricular tachycardia
Idioventricular, ventricular, or escape beats or rhythm
Aberration
Fixed interventricular conduction defect
Antidromic reciprocating tachycardia
Pacemaker-mediated tachycardia

Differential diagnosis of wide-complex rhythms. AV = atrioventricular; SVT = supraventricular tachycardia; WPW = Wolff-Parkinson White syndrome.

Workup

Laboratory Studies

• Individualized laboratory investigations
  • Acute symptomatic or sustained ventricular arrhythmia (VA) generally warrants relatively intensive laboratory investigation.
  • The yield of these tests is typically low when the history, physical findings, and other aspects of the patient's presentation do not suggest specific findings.
  • Most of these studies are omitted in patients with asymptomatic arrhythmia with apparently normal hearts.
• Serum electrolyte determinations
  • Hyperkalemia and hypokalemia, regardless of their cause, are associated with increasing ventricular ectopy and may affect repolarization.
  • Severe hypocalcemia, as seen in rickets, can prolong QT intervals and permit polymorphic ventricular tachycardia (VT).
  • Hypomagnesemia may be clinically important in patients with cardiac conditions during the immediate postoperative period and in certain other settings.
• Toxicology
  • Administration of multiple therapeutic drugs or abuse of recreational drugs can trigger VA.
  • Pay particular attention to tricyclic antidepressant (TCA) overdose, use of drugs that may affect the potassium channel (eg, cisapride), and stimulant ingestion.
• Thyroid function testing
  • Although typically associated with other clinical features of hyperthyroidism, elevated thyroxine levels may increase a patient's underlying arrhythmia or may trigger a new arrhythmia.
  • Pay particular attention to thyroid function in patients with a history of amiodarone use.
• Other laboratory studies
  • Other laboratory data, including transaminases and bilirubin levels, may be required to make decisions about drug therapy.
  • Both ABGs and central venous oxygen saturations may help in assessing the hemodynamic severity of arrhythmia in some patients.
  • Genetic testing is now commercially available for many of the genes related to hypertrophic cardiomyopathy (HCM), long QT syndrome (LQTS), Brugada syndrome, and catecholaminergic polymorphic VT.
    • Even with clear clinical diagnoses, as many as 30% of patients with LQTS have negative results on genetic testing, and as many as 80% of patients with Brugada syndrome have negative results on testing.
    • Limited testing is also available for arrhythmogenic right ventricular dysplasia (ARVD). 
    • Some insurers do not cover these tests, which can result in prohibitively expensive charges.
    • Updated genetic testing data are summarized on the GeneTests Web site.
    • Genetic testing is exceptionally valuable when evaluating an extended family where the gene is clearly identified and testing can be narrowly focused.
    • For an individual patient with clinical ambiguity genetic testing remains a tool that often requires detailed judgment. With LQTS, a significant number of mutations are reported that have not been demonstrated to have adverse clinical or cellular electrophysiology effects. 

Imaging Studies

• Chest radiography: Chest radiography allows for a rapid assessment of ventricular dilatation, pulmonary venous pressure, and mechanical influences (eg, intracardiac catheters). With ready access to echocardiography, the importance of chest radiography has decreased. 
• Echocardiography: All patients with clinically significant ectopy should undergo a complete echocardiographic examination, ideally in a laboratory skilled in examining children. The following specific details may be sought:
  • Ventricular function (on sinus beats)
  • Wall thickness
  • Proximal coronary artery pattern, including efforts to visualize Doppler flow
  • Tumors
  • Structural heart disease
• Cardiac MRI: The use of MRI is evolving. Although indications for MRI are uncertain, cardiac MRI is used primarily to assess ARVD and tumors.
  • When the rhythm is irregular, gating may be insufficient to acquire adequate images.
  • Although MRI is a popular imaging modality, data from critical analysis suggest that MRI may result in overdiagnosis of ARVD.¹⁴ Not surprisingly, the test is quite reasonable in adult patients who already meet Task Force Criteria for arrhythmogenic right ventricular cardiomyopathy (ARVC).¹⁵
    • Specific techniques involving delayed enhancement may improve discrimination.
    • The role of MRI is particularly challenging in patients with a low previous probability of the disease¹⁶ and in younger patients whose fibrofatty infiltrate may not have progressed.¹⁷

Other Tests

• Electrocardiography
  • An ECG with a rhythm strip allows for a rapid initial analysis of the morphology, frequency, and electrical substrate of suspected arrhythmia. ECG helps to exclude supraventricular tachycardia (SVT) or atrial arrhythmias with fixed bundle-branch block (BBB) or rate-dependent aberrancy. Leads aVF, V1, and V6 provide sufficient data to classify BBB morphology and estimate frontal-plane axes.
  • In combination with ambulatory or bedside monitoring systems, ECG provides sufficient data for initial diagnosis of most VAs.
  • Holter monitoring: A 24-hour Holter evaluation provides a quantitative daily snapshot of ventricular ectopy. In patients with suspected cardiac syncope, pay particular attention to QT intervals and T-wave changes for hints of underlying disease. The Holter QTc and ECG measurement of QTc do not have a 1:1 correlation; good data are not available regarding absolute QT/QTc measurements using the rapid sweep speed and high gain typically used in Holter monitoring.
  • Memory-looping event monitoring: Episodic correlation is best performed by using a memory-looping event monitoring system.
    • Some memory-looping monitors are worn and make continuous recordings. These devices record and hold the waveform before patients activate them.
    • Other nonlooping "memo" versions are not worn continuously. These systems do not record continuously. Instead, they are activated on symptom onset and, therefore, frequently miss the symptomatic event. They are quite effective in patients with sustained arrhythmias.
    • Memory-looping systems are preferable for nonsustained arrhythmias or evanescent symptoms because they can capture the start of a rhythm and because they are most likely to be recording during symptoms. The yield on either system declines rapidly after 2-3 weeks of use. 
    • New surgically implantable, subcutaneous systems may allow for the correlation of symptoms and rhythms in selected patients.^18,19
    • Continuous multilead home telemetry is now marketed as a way in increasing the yield of ambulatory monitoring.²⁰  
  • Exercise ECG
    • Exercise typically suppresses benign arrhythmia. The converse is probably a more valid finding because increasing arrhythmia density and complexity with exercise suggests more problematic mechanisms. 
    • Repeated exercise tests may help in assessing the adequacy of medication and other therapeutic choices. Treadmill exercise is generally more effective at recreating arrhythmias and permits more effective evaluation of blood pressure adaptation in hypertrophic cardiomyopathy (HCM), syncope, and other clinical scenarios. 
    • Overall, exercise testing enhances the sensitivity of ECG monitoring, although it has uncertain reproducibility and specificity.
    • In adults with decreased left ventricular function, the presence of microvolt T-wave alternans is strongly associated with both ventricular arrhythmias and sudden cardiac arrest. In the pediatric population, although T-wave alternans do seem to be associated with serious VAs, other variables offer more information. In both settings, the absence of microvolt T-wave alternans appears to help select patients at lower risk.²¹ Reimbursement and technical issues have limited the use of the test.
  • Signal Averaged ECGs (SAECG): Commercial systems permit relatively easy acquisition of SAECGs and identification of late potentials. Many high-risk patients with congenital heart disease (CHD) have BBBs or paced rhythms, making the test invalid. Like T-wave alternans, the test is not widely used, with the exception of longitudinal evaluation of patients with suspected ARVC.  
• Drug challenges: Selected patients may be given serial trials of drugs to either provoke or suppress arrhythmia.

Procedures

• Cardiac catheterization remains controversial and is generally reserved for patients with severe symptoms or arrhythmia in whom adequate diagnosis and risk assessment are impossible with noninvasive testing. Cardiac catheterization may provide information, as described below.
  • Myocardial biopsy: Patients with ventricular ectopic rhythms, particularly those with depressed function, may have myocarditis that warrants therapy.
  • Hemodynamic study: Although echocardiography and other noninvasive tests are excellent, catheterization provides a measurement of hemodynamics in patients with VA who undergo catheterization for other indications.
  • Coronary angiography: Except in selected patients with premature coronary artery disease (eg, after heart transplantation), the primary issue is whether abnormalities are present in the origin of the coronaries and in their proximal course. Selective coronary angiography is often necessary to address this issue. Both echocardiography and cardiac MRI are excellent noninvasive imaging tools to visualize the proximal coronary arteries.
  • Right ventriculography: This study may help to diagnose ARVD and facilitate mapping studies.
• Programmed atrial and ventricular stimulation are reasonably effective in reproducing reentrant VA.
  • For patients with CHD,^22,23 suspected Brugada syndrome, or suspected ARVD, programmed stimulation may assist in risk stratification or diagnosis.
  • Voltage mapping in ARVD may assist in identifying areas of low amplitude ventricular signals in the right ventricular free wall and septum that represent substrates for reentry.
  • Intracardiac recordings and the use of temporary or esophageal wires allow for a firm diagnosis when surface ECGs are unclear.
• Programmed stimulation is typically not useful for triggering or excluding automatic ventricular rhythms, which are most common in childhood and adolescence.

Histologic Findings

• Histologic findings depend on the ultimate diagnosis.
• Many patients with serious arrhythmia have entirely normal results on light and electron microscopy.
• Fibrosis or inflammation may influence therapy.

Treatment

Medical Care

• Therapy may not be needed in asymptomatic patients whose ventricular tachycardia (VT) patterns suggest a low risk of sudden death. Symptoms or a clinically significant short-term risk of sudden cardiac death (SCD) frequently warrants admission for evaluation and consideration of therapeutic options.
• Initial therapy for ventricular fibrillation is immediate, unsynchronized direct current (DC) defibrillation. Data suggest that a brief (ie, 90 s) period of chest compressions may improve survival when ventricular fibrillation is witnessed, but immediate defibrillation is the therapy of choice. Do not waste time on other aspects of resuscitation before initial defibrillation, unless defibrillation is unavailable.
• Identify and target potential substrates for arrhythmia-specific therapy.
• Optimal inpatient management is performed with secure vascular access and continuous cardiac monitoring. In the ideal case, cardiac monitoring systems are connected to a central monitoring station in a cardiac care unit or ICU. Simple bedside monitors with high-rate and low-rate alarms are inadequate to monitor patients with the potential for unstable ventricular arrhythmia (VA).
• For unstable patients, conduct simultaneous evaluation and therapy.
• For hemodynamically stable patients, evaluation is followed by serial drug therapy. Diagnostic or therapeutic catheterization also may be performed.

Surgical Care

Selected patients require highly individualized interventional procedures, such as the following:

• Excisional biopsy: Incessant VT is sometimes secondary to focal lipoid cardiomyopathy, isolated fibromas, or hamartomas. In selected patients, surgical excision may be both diagnostic and therapeutic.
• Implantable cardioverter/defibrillators (ICDs): ICDs have revolutionized the care of adults with high-risk VT after myocardial infarction. ICDs are increasingly used in high-risk pediatric patients.^24,25 Transvenous systems have been used in patients who weigh as little as 20 kg. In highly selective situations, toddlers and large infants have received epicardial systems implanted through a sternotomy.²⁶ Creative, hybrid approaches are further increasing clinicians' willingness to use ICDs in young patients (see Media file 3).
• Radiofrequency catheter ablation or cryoablation: Both catheter-directed radiofrequency ablation and intraoperative resection or cryoablation of VT foci have been successful with monomorphic VTs; however, their use is unproved for patients with polymorphic VT. Unlike supraventricular arrhythmias, for which catheter ablation has a more than 95% success rate, VT ablation in pediatric patients and in patients with congenital heart disease (CHD) has a success rate of about 60%.^27,28 Both a lack of arrhythmia and proximity to the bundle of His limit the ability to provide effective therapy.
• Left cervical sympathectomy: For many years, this procedure was performed for refractory long QT syndrome (LQTS). Although it may still have a role when performed by skilled surgeons, many groups now choose a combination of pharmacologic alpha-blockade and beta-blockade, often with ICD placement.

Consultations

• Patients should be referred to a cardiologist.
• Primary care physicians may certainly observe infrequent asymptomatic premature ventricular contractions (PVCs), often with a 24-hour Holter evaluation, to confirm the frequency and severity of arrhythmia. For most other patients with VA more complex than this, prompt referral and direct communication with a pediatric cardiologist is indicated. Referral facilitates appropriate testing and decision making about evaluating the patient on an inpatient or outpatient basis.
• The patterns and relative risks of arrhythmia in adult and pediatric patients differ substantially. Whenever feasible, a cardiologist with specific training and expertise in pediatric heart disease should evaluate the patient. Expedite referral when any of the following indications are present:
  • Symptoms of syncope or apparent heart failure
  • Family history of premature death or seizures
  • History or physical suggesting structural heart disease or heart failure
  • Arrhythmia triggered by medications
  • Arrhythmia triggered by recreational drugs
  • Nonsustained or sustained VT
  • History of cardiac surgery or known heart disease, even if it is apparently repaired

Diet

• Diet is rarely is a factor in VA.
• Diuretic use or abuse, anorexia, or chronic diarrhea can induce hypokalemia, which exacerbates VA.
• Primary or dietary rickets rarely produces sufficient hypocalcemia to cause QT prolongation and a risk of arrhythmia.

Activity

• The updated 2005 Bethesda conference offers useful initial set of recommendations for patients with ventricular ectopy.²⁹
  • In the absence of detailed investigations and referral, the activity of patients with PVCs that are more than isolated is typically restricted to low-static or low-dynamic activities.
  • Similar restrictions are recommended for those with clinically significant ectopy and most forms of heart disease or symptoms.
  • Patients whose findings on subsequent investigation suggest benign VT often may resume their full activities.
  • Detailed recommendations for both patients with inherited heart disease and those with CHD have been updated in the 36th Bethesda Conference.³⁰
• Exercise represents a paradox because its long-term health benefits may lower the overall incidence of cardiac events, but the instantaneous risk of cardiac events appears to increase during or immediately after exertion. Some patients with prolonged-QT syndrome have drowned, particularly after diving into cold water, presumably because they developed ventricular fibrillation.
• Elite athletes, particularly males, may have an athletic heart syndrome that can include mildly increased left ventricular mass with normal left ventricular cavity dimensions. One third of these patients have more than 100 premature ventricular beats per 24 hours with other higher grade ectopy, including couplets and nonsustained VT.

Medication

Although antiarrhythmic drug therapy can suppress spontaneous arrhythmia and although it may help individual patients, some of these medications have increased mortality rates in selected adult and pediatric patients. Mortality rates typically increase when the overall risk is less than the risk of proarrhythmia. Although digoxin is approved for use in infants, it lacks specific antiarrhythmic properties that aid in the control of most ventricular arrhythmias. All other agents, despite the current use, are not approved for use in young children.

Antiarrhythmic drug therapy is further complicated because no single drug is ideal in all settings. Beta-blockade, with intravenous (IV) esmolol or any of the oral (PO) preparations, is a good initial choice for nearly all forms of ventricular arrhythmia (VA). In addition, it has few absolute contraindications in the treatment of serious arrhythmia.

Other medications have important limitations. Use of verapamil in children younger than 1 year is associated with infrequent episodes of cardiovascular collapse and death. Procainamide is an excellent choice for incessant reentrant VA in many settings, but it may exacerbate long QT syndrome (LQTS). PO agents in Vaughn-Williams class I-A (eg, quinidine, procainamide), class I-C (eg, flecainide, propafenone), or class III (eg, sotalol, amiodarone) can cause ventricular proarrhythmia and suppress clinical arrhythmia while increasing mortality rates in selected populations. Both IV and PO amiodarone may have important noncardiac adverse effects. Make therapeutic decisions carefully after consulting with an experienced pediatric cardiologist (electrophysiologist).

Intravenous amiodarone in infants and young children deserves particular attention. The medications broad efficacy and ready availability has increased in popularity in managing sustained arrhythmias in the ICU and emergency setting. A prospective tiered dose pediatric trial showed good efficacy but a nearly 50% incidence of major adverse events.³¹

Neonates may have relatively frequent episodes of nonsustained ventricular tachycardia or, more precisely, accelerated idioventricular rhythm (AIVR). Although thorough noninvasive evaluation with monitoring and echocardiography is warranted, the risk of mortality is probably zero. Similarly, the risks associated with many forms of VA are quite low in the patient without cardiomyopathy or a probable ion-channel defect. In both of these settings, avoiding therapy with potentially risky drugs and then choosing an agent that is more effective at decreasing arrhythmias on ambulatory monitoring may be important.

Beta-blockers

Propranolol, atenolol, nadolol, and esmolol are the beta-blockers most frequently used to manage VA. They appear to be particularly effective in treating patients with VA, LQTS, or HCM. Other agents may be useful; sotalol, propafenone, and amiodarone have beta-blocking properties. Beta-blockers have not been associated with ventricular proarrhythmia; this is a major advantage of this class compared with other agents, particularly class I and III agents. Base the choice between beta-blockers on the duration of action, selectivity, and preparation.

Propranolol (Inderal)

Nonselective beta-blocker with long record of use and relative safety. Generally short acting, but long-acting preparations available. Stable liquid preparation can be used to treat infants. Significant efficacy data available.

Dosing

Adult

80-240 mg/d PO divided q6-8h; or qd as SR preparation

Pediatric

PO: 1-4 mg/kg/d divided q6-8h
IV: Not recommended; however, for arrhythmias, 0.01-0.1 mg/kg, not to exceed 1 mg/dose slow bolus recommended; change to PO as soon as possible

Interactions

Coadministration with aluminum salts, barbiturates, nonsteroidal anti-inflammatory drugs (NSAIDs), penicillins, calcium salts, cholestyramine, and rifampin may decrease effects; calcium channel blockers, cimetidine, loop diuretics, and monoamine oxidase inhibitors (MAOIs) may increase toxicity; may increase toxicity of hydralazine, haloperidol, benzodiazepines, and phenothiazines

Contraindications

Documented hypersensitivity; uncompensated congestive heart failure (CHF), bradycardia, cardiogenic shock, AV conduction abnormalities, severe ventricular dysfunction; severe asthma; diabetes

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Asthma and bronchospasm; AV conduction disturbance; depression; bradycardia; hypoglycemia in infants; beta-adrenergic blockade may decrease signs of acute hypoglycemia and hyperthyroidism; abrupt withdrawal may exacerbate symptoms of hyperthyroidism, including thyroid storm; withdraw slowly and monitor closely; infants may have clinically important hypoglycemia, particularly when PO intake impaired

Atenolol (Tenormin)

Cardioselective beta1-blocker. Compared with propranolol, may have better tolerability and pharmacokinetics, and frequently has equivalent efficacy.

Dosing

Adult

25-100 mg/d PO qd; divided q12h in some settings, particularly in adolescents

Pediatric

0.1-0.3 mg/kg/d PO qd or divided q12h

Interactions

Coadministration with Al salts, barbiturates, Ca salts, cholestyramine, NSAIDs, penicillins, and rifampin may decrease effects; haloperidol, hydralazine, loop diuretics, and MAOIs may increase toxicity

Contraindications

Documented hypersensitivity; uncompensated CHF, bradycardia, cardiogenic shock, AV conduction abnormalities, severe ventricular dysfunction; severe asthma; diabetes

Precautions

Pregnancy

D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus

Precautions

Asthma and bronchospasm; AV conduction disturbance; depression; bradycardia; hypoglycemia in infants; beta-adrenergic blockade may reduce symptoms of acute hypoglycemia and mask signs of hyperthyroidism; abrupt withdrawal may exacerbate symptoms of hyperthyroidism and cause thyroid storm; monitor patients closely and withdraw drug slowly

Nadolol (Corgard)

Nonselective beta-blocker that has more favorable pharmacokinetics than propranolol, which may increase efficacy in some settings.

Dosing

Adult

40-240 mg/d PO qd or divided q12h in some settings

Pediatric

1-2 mg/kg/d PO qd or divided q12h

Interactions

Exogenous catecholamines; antihypertensive agents; calcium channel blockers exaggerate negative inotropic and chronotropic effects

Contraindications

Documented hypersensitivity; uncompensated CHF, bradycardia, cardiogenic shock; AV conduction abnormalities, severe ventricular dysfunction; severe asthma; diabetes

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Asthma and bronchospasm; AV conduction disturbance; depression; bradycardia; hypoglycemia in infants; beta-adrenergic blockade may reduce symptoms of acute hypoglycemia and mask signs of hyperthyroidism; abrupt withdrawal may exacerbate symptoms of hyperthyroidism and cause thyroid storm; monitor patients closely and withdraw drug slowly

Esmolol (Brevibloc)

Short-acting, IV, beta1-blocker useful in acute care settings.

Dosing

Adult

Loading dose: 0.5 mg/kg/min IV; then IV infusion 50-200 mcg/kg/min, increase q5-10min until maximum acceptable dose or efficacy

Pediatric

Loading dose: 0.5 mg/kg IV; then IV infusion 100-500 mcg/kg/min IV, increase q5-10min until maximum acceptable dose or efficacy; if significant ventricular dysfunction, consider test dose of 0.25 mg/kg IV and observe effects

Interactions

Cardiotoxicity may increase with concurrent sparfloxacin, astemizole, calcium channel blockers, quinidine, flecainide, and contraceptives; concurrent digoxin, flecainide, acetaminophen, clonidine, epinephrine, nifedipine, prazosin, haloperidol, phenothiazines, and catecholamine-depleting agents increase toxicity

Contraindications

Documented hypersensitivity; uncompensated CHF, bradycardia, cardiogenic shock; AV conduction abnormalities, severe ventricular dysfunction; severe asthma; diabetes

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Asthma and bronchospasm; AV conduction disturbance; depression; bradycardia; hypoglycemia in infants; beta-adrenergic blockade may reduce symptoms of acute hypoglycemia and mask signs of hyperthyroidism; abrupt withdrawal may exacerbate symptoms of hyperthyroidism and cause thyroid storm

Betaxolol (Kerlone)

Long-acting, PO, highly selective beta1-blocker that decreases automaticity of cardiac contractions. Potential adverse effects same as those of other beta-blockers, but high beta1-selectivity of drug (or bisoprolol) may permit low doses that avoid adverse effects.

Dosing

Adult

10 mg PO qd initially; may increase to 40 mg/d
Severe renal impairment: 5 mg PO qd initially; may increase by 5-mg increments q2wk, not to exceed 20 mg/d

Pediatric

Not established

Interactions

Cardiotoxicity may increase with concurrent sparfloxacin, astemizole, calcium channel blockers, quinidine, flecainide, and contraceptives; concurrent digoxin, flecainide, acetaminophen, clonidine, epinephrine, nifedipine, prazosin, haloperidol, phenothiazines, and catecholamine-depleting agents increase toxicity

Contraindications

Documented hypersensitivity; uncompensated CHF, bradycardia, cardiogenic shock; AV conduction abnormalities, severe ventricular dysfunction; severe asthma; diabetes

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Asthma, bronchospasm, AV conduction disturbance, depression; bradycardia; hypoglycemia in infants; beta-adrenergic blockade may reduce symptoms of acute hypoglycemia and mask signs of hyperthyroidism; abrupt withdrawal may exacerbate symptoms of hyperthyroidism and cause thyroid storm; decrease dose in renal impairment

Class I antiarrhythmics

This class of agents has complex actions. The drugs primarily block sodium channels, decreasing conduction velocity (QRS widening). Only IV procainamide and lidocaine are presented here. Quinidine, the initial drug in this class, is associated with excessive ventricular proarrhythmia in most patient groups. Propafenone, disopyramide, flecainide, and other agents may have a role in long-term therapy in some patients. Some children and adults with ischemic heart disease have increased mortality rates while taking these medications despite apparent control of their arrhythmia.

Procainamide (Procanbid, Pronestyl)

Once mainstay of PO therapy, long-term use associated with lupuslike syndrome. With important exception of LQTS, torsadelike polymorphic VT, and related disorders, controls both ventricular and supraventricular arrhythmias. Hypotension and reflex increase in AV conduction important adverse effects to consider. Therapeutic levels of procainamide and N -acetyl-procainamide (NAPA; major, active metabolite), can be monitored.

Dosing

Adult

Loading dose: 500-1000 mg IV over 20-60 min
Maintenance infusion: 2-6 mg/min IV

Pediatric

Loading dose: 5-10 mg/kg IV over 20-60 min
Maintenance infusion: 20-40 mcg/kg/min IV; infants may need up to 80 mcg/kg/min

Interactions

Increases levels of NAPA in patients taking cimetidine, ranitidine, beta-blockers, amiodarone, trimethoprim, and quinidine; may increase effects of skeletal muscle relaxants, quinidine, lidocaine, and neuromuscular blockers; ofloxacin inhibits tubular secretion and may increase bioavailability; may increase risk of cardiotoxicity with concurrent sparfloxacin

Contraindications

Documented hypersensitivity; LQTS, second- or third-degree heart block, complete heart block, torsade de pointes; systemic lupus erythematosus (SLE)

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Monitor for hypotension; plasma concentrations of procainamide and NAPA may increase in renal failure; high or toxic concentrations may induce AV block or abnormal automaticity; caution in complete AV block, digitalis intoxication, organic heart disease, renal disease, and hepatic insufficiency

Lidocaine (Xylocaine IV for Cardiac Arrhythmias)

Class I-B antiarrhythmic. Mainstay in IV suppression of VA in adults with ischemic heart disease; less clearly effective in children, though has advantage of general safety. Generally tolerated by patients with poor ventricular function and potentially effective in virtually every setting of serious VA.

Dosing

Adult

Loading dose: 50 mg IV; repeat q3-5min not to exceed cumulative dose of 200 mg
Maintenance infusion: 1-4 mg/min IV

Pediatric

Loading dose: 1 mg/kg IV; repeat in 10-15 min for 2 doses
Maintenance infusion: 20-50 mcg/kg/min IV

Interactions

Coadministration with cimetidine or beta-blockers increases toxicity; coadministration with procainamide and tocainide may result in additive cardiodepressant action; may increase effects of succinylcholine

Contraindications

Documented hypersensitivity to amide-type local anesthetics; avoid in Adams-Stokes syndrome and Wolff-Parkinson-White syndrome; avoid in severe sinoatrial, AV, or intraventricular block, if artificial pacemaker not in place

Precautions

Pregnancy

B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals

Precautions

Use solution without preservatives; caution in heart failure, hepatic disease, hypoxia, hypovolemia or shock, respiratory-depression, and bradycardia; may increase risk of CNS and cardiac adverse effects in older patients; high plasma concentrations can cause seizures, heart block, and AV conduction abnormalities

Class III antiarrhythmics

Amiodarone is generally reserved for potentially life-threatening VA. It elicits potassium channel blockade and prolongs repolarization.

Amiodarone (Cordarone)

Complex and potent antiarrhythmic agent with several actions on cardiac action potential, exceedingly complex pharmacokinetics, and extracardiac pharmacodynamics. May inhibit AV conduction and sinus-node function. Prolongs action potential and refractory period in myocardium and inhibits adrenergic stimulation.
PO efficacy may take weeks. With exception of disorders of prolonged repolarization (eg, LQTS), may be drug of choice (DOC) for life-threatening VA refractory to beta-blockade and initial therapy with other agents.

Dosing

Adult

Loading dose: 800-1600 mg/d PO divided in 1-2 doses/d for 1-3 wk, then 600-800 mg/d divided in 1-2 doses/d for 1 mo
Maintenance dose: 400 mg/d PO
Alternative IV loading dose: 150 mg IV over first 10 min, then 360 mg over next 6 h, then 540 mg over next 18 h; IV must be further diluted before administration

Pediatric

Loading dose: 10-15 mg/kg/d PO divided in 1-2 doses/d for 1-3 wk, then 2-6 mg/kg/d divided in 1-2 doses/d for 1 mo
Alternative IV loading dose: 2-3 mg/kg IV over 5-10 min, repeat bolus q10-30min; not to exceed cumulative dose of 10-15 mg/kg/d

Interactions

Increases effect and blood levels of theophylline, quinidine, procainamide, phenytoin, methotrexate, flecainide, digoxin, cyclosporine, beta-blockers, and anticoagulants; protease inhibitors (eg, indinavir, ritonavir, amprenavir, nelfinavir) inhibit amiodarone metabolism resulting in increased serum levels and may prolong the QT interval; cardiotoxicity increased by sparfloxacin, and disopyramide; coadministration with calcium channel blockers may cause additive effect and further decrease myocardial contractility; cimetidine may increase amiodarone levels; drugs that prolong QTc (eg, dofetilide, sotalol) likely to have additive effect

Contraindications

Documented hypersensitivity; complete AV block, intraventricular conduction defects; patients taking ritonavir or sparfloxacin

Precautions

Pregnancy

D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus

Precautions

IV preparation may induce hypotension (Ca may reverse); carefully monitor pulmonary function, corneal staining, thyroid function; caution in thyroid or liver disease; caution in electrolyte imbalance (ie, hypokalemia, hypomagnesemia); in infants and young children, incidence of serious adverse events significant, and patients may require pacing or other support

Calcium channel blockers (Vaughn-Williams class IV)

Verapamil is primarily marketed to control hypertension or heart rate during atrial tachycardia.

Verapamil (Calan, Verelan)

Can diminish PVCs associated with perfusion therapy and decrease risk of ventricular fibrillation and VT. By interrupting reentry at AV node, can restore normal sinus rhythm in patients with paroxysmal SVTs (PSVTs). IV and PO. Some automatic VTs and RBBB reentrant VT in normal hearts often sensitive. Fatal cardiovascular collapse reported in infants and neonates given IV form. PO preparations include short-acting (q6h) and sustained-release (SR) preparations for qd dosing.

Dosing

Adult

IV: 2.5-10 mg; 5 mg typical
PO: 180-320 mg/d divided q6h; extended-release (ER) form may be administered qd

Pediatric

IV: 0.1-0.3 mg/kg/dose, not to exceed 5 mg/dose; use with extreme caution in infants (severe apnea, bradycardia, hypotensive reactions, and cardiac arrest have occurred)
PO: 3-7 mg/kg/d divided q6h; ER form may be administered qd in older patients

Interactions

May increase carbamazepine, digoxin, and cyclosporine levels; coadministration with amiodarone can cause bradycardia and decrease cardiac output; with concurrent beta-blockers, may increase cardiac depression; cimetidine may increase levels; may increase theophylline levels

Contraindications

Documented hypersensitivity; severe CHF, sick sinus syndrome, second- or third-degree AV block; hypotension (<90 mm Hg systolic); infants

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

AV conduction disturbance and bradycardia may occur, monitor ECG and blood pressure closely; monitor liver function

Follow-up

Further Inpatient Care

• Admit patients with new and unprotected symptoms of apparent cardiac syncope to a monitored setting to ensure their safety during evaluation.
• Perform intracardiac procedures, some of which may be performed as same-day admissions.
• Revise or place implantable defibrillators.
• Initiate antiarrhythmic therapy.

Further Outpatient Care

• Patients with conditions beyond asymptomatic, isolated, premature ventricular beats should receive episodic monitoring of their clinical status. They may require repeated assessment of ventricular function with echocardiography, repeated Holter or event monitoring, and monitoring for drug effects when drugs are used.
• Device-based therapy requires a follow-up system to evaluate and manage the consequences and complications of therapy.

Transfer

• Patients with apparent cardiac syncope and ventricular arrhythmia (VA) require prompt evaluation by a cardiologist.
• Transfer the patient to a setting that can ensure adequate monitoring, skilled nursing, and an experienced pediatric cardiology team.

Deterrence/Prevention

• With the possible exceptions of hypertrophic and dilated cardiomyopathy, sudden death remains rare, even in pediatric patients at relatively high risk. The presentation of patients with potentially lethal disease may not be dramatic. One of the most powerful deterrents is for clinicians to recognize that rare, but serious, diagnoses can be identified and treated.
• Deterrence efforts are aimed primarily at decreasing the consequences of VA (eg, sudden death, tachycardia-mediated cardiomyopathy). For many rhythms, complete suppression is neither warranted nor advisable. Carefully monitor the administration of drugs that affect repolarization (eg, cisapride, major antipsychotics, tricyclic antidepressants [TCAs]) because monitoring may decrease the risk of torsade de pointes in patients taking these medications.
• Prudent preventive measures for patients with VA include avoiding known triggers and sustained drug use, especially recreational drug use.
• Therapy with beta-blockers and possibly other medications may help decrease the risk in patients with hypertrophic cardiomyopathy (HCM) and in symptomatic patients with long QT syndrome (LQTS). No particular therapy clearly prolongs survival in high-risk patients with dilated cardiomyopathy or congenital heart disease (CHD).

Complications

• Complications occur both as a result of the arrhythmia and of the therapy. The most devastating risk is sudden cardiac death (SCD) or aborted sudden death with subsequent hypoxic-ischemic brain injury.
• Incessant arrhythmia may induce reversible myopathy, and even transient arrhythmic events can produce head injury with sequelae.
• Therapy poses numerous predictable risks, including proarrhythmia and infection from implantable devices.

Prognosis

• The prognosis cannot be generalized; it must be individualized and based on the underlying diagnosis.

Patient Education

• Patients with VA and their families must know how to perform cardiopulmonary resuscitation (CPR) and how to contact local emergency medical services (EMS) to promptly begin therapy or prevent excessive therapy, as warranted. Not all patients need a home ambulatory external defibrillator (AED).
• Perform family screening when the results of initial patient assessment suggest familial disease (eg, HCM, LQTS).
• For excellent patient education resources, visit eMedicine's Heart Center. Also, see eMedicine's patient education article Tetralogy of Fallot.

Miscellaneous

Medicolegal Pitfalls

• Failure to identify hypertrophic cardiomyopathy (HCM) or long QT syndrome (LQTS)
• Failure to identify affected family members with familial diseases (eg, HCM, LQTS)
• Poor communication of the risk factors to the family and patient
• Inappropriate choices regarding workup and therapy for many kinds of VT
• Lack of referral to an experienced center
• Excessive concern and therapy for low-risk arrhythmia
• Inappropriate drug selection and/or monitoring

Multimedia

Media file 1: Relative sudden death (arrhythmia) and overall mortality rates for representative types of congenital heart disease. ASD = Atrial septal defect; PDA = Patent ductus arteriosus; VSD = Ventricular septal defect; PS = Valvar pulmonary stenosis; CAVC = Common atrioventricular canal defect; COA = Aortic coarctation; TOF = Tetralogy of Fallot; D-TGA = D-transposition of the great vessels, primarily using atrial switch; AS = Aortic stenosis.

Media file 2: Ventricular arrhythmias with changing substrate. TOF = Tetralogy of Fallot; LATE = Repaired after age 4 years, follow-up after age 12 years. EARLY = Repair before age 1 year, follow-up at age 1 year and age 5 years.

Media file 3: Differential diagnosis of wide-complex rhythms. AV = atrioventricular; SVT = supraventricular tachycardia; WPW = Wolff-Parkinson White syndrome.

Media file 4: Novel pacemaker implantable cardioverter/defibrillator (ICD) in a 14-kg, 3-year-old patient with a long QT, a history of 2:1 block, and an SCN5A mutation. Two bipolar epicardial sew-on leads are used for atrial and ventricular pacing and sensing. A standard single-coil, 45-cm ICD lead is placed along the posterior pericardium and is secured by using the extendable screw. The pacing/sensing portion of that lead is capped and left in the pocket.

Media file 5: ECG in a 12-year-old boy.

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Keywords

ventricular tachycardia, nonsustained ventricular tachycardia, accelerated ventricular rhythms, premature ventricular contractions, PVC, repetitive monomorphic ventricular tachycardia, sustained monomorphic ventricular tachycardia, torsade de pointes, ventricular ectopic activity, VEA, ventricular ectopy, ventricular fibrillation, V fib, ventricular flutter, V flutter, ventricular premature beats, ventricular arrhythmia, VA, VT, V tach, sudden cardiac death, syncope, congenital heart disease, long QT syndrome, LQTS, tetralogy of Fallot, ventricular fibrillation, aortic stenosis, hypertrophic cardiomyopathy, HCM, ventricular septal defects, Chagas disease, trypanosomiasis, Brugada syndrome, cocaine, tricyclic antidepressant use, Kawasaki disease, right bundle-branch block, RBBB, right ventricular outflow tract ventricular tachycardia, left bundle-branch block, LBBB

Contributor Information and Disclosures

Author

Mark E Alexander, MD, Assistant Professor, Department of Pediatrics, Children's Hospital of Boston and Harvard Medical School
Mark E Alexander, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, Heart Rhythm Society, and Pediatric Electrophysiology Society
Disclosure: Nothing to disclose.

Coauthor(s)

Charles I Berul, MD, Associate Professor of Pediatrics, Harvard Medical School; Senior Associate, Department of Cardiology, Children's Hospital of Boston
Charles I Berul, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, American Heart Association, Heart Rhythm Society, and Society for Pediatric Research
Disclosure: Nothing to disclose.

Medical Editor

Christopher Johnsrude, MD, Associate Professor of Pediatrics, Director of Electrophysiology, University of Louisville School of Medicine; Consulting Staff, Pediatric Cardiology Associates, PSC
Christopher Johnsrude, MD is a member of the following medical societies: American Academy of Pediatrics and American College of Cardiology
Disclosure: Nothing to disclose.

Pharmacy Editor

Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine
Disclosure: Pfizer Inc Stock Investment from financial planner; Avanir Pharma Stock Investment from financial planner ; WebMD Salary and stock Employment and investment from financial planner

Managing Editor

Hugh D Allen, MD, Professor, Department of Pediatrics, Division of Pediatric Cardiology and Department of Internal Medicine, Ohio State University College of Medicine
Hugh D Allen, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, American Heart Association, American Pediatric Society, American Society of Echocardiography, Society for Pediatric Research, Society of Pediatric Echocardiography, and Western Society for Pediatric Research
Disclosure: Nothing to disclose.

CME Editor

Gilbert Herzberg, MD, Assistant Professor, Department of Pediatrics, Section of Pediatric Cardiology, New York Medical College
Gilbert Herzberg, MD is a member of the following medical societies: American Academy of Pediatrics
Disclosure: Nothing to disclose.

Chief Editor

Stuart Berger, MD, Professor of Pediatrics, Division of Cardiology, Medical College of Wisconsin; Chief of Pediatric Cardiology, Medical Director of Pediatric Heart Transplant Program, Medical Director of The Heart Center, Children's Hospital of Wisconsin
Stuart Berger, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, American College of Chest Physicians, American Heart Association, and Society for Cardiac Angiography and Interventions
Disclosure: Nothing to disclose.

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