Asymptomatic Wolff-Parkinson-White Preexcitation Syndrome in Children

From The Child's Doctor, Fall 2012

Sabrina Tsao, MD

Attending physician, Cardiology; Assistant Fellowship Director, Pediatric Cardiology, Ann & Robert H. Lurie Children's Hospital of Chicago; Assistant professor of Pediatrics, Northwestern University Feinberg School of Medicine

Disclosure: Dr. Tsao has no industry relationships to disclose and does not refer to products that are still investigational or not labeled for the use in discussion.

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With increased use of ECG screening, more children are diagnosed with asymptomatic Wolff-Parkinson-White (WPW) syndrome, or isolated ventricular preexcitation. While catheter ablation can be curative, it is not without risk and is not appropriate for every child with asymptomatic WPW. To help physicians determine the risk of sudden cardiac death in these patients and whether catheter ablation is needed, the Pediatric and Congenital Electrophysiology Society (PACES) and Heart Rhythm Society (HRS) recently released the first expert consensus statement on the evaluation and management of asymptomatic WPW in patients 8-21 years of age.[1] This article will review risk stratification through non-invasive and invasive testing strategies and discuss other considerations in the management of children without symptoms who are found to have a WPW pattern on ECG.

Definition

The term “Wolff-Parkinson-White” (WPW) was first used to describe ECG finding of “bundle-branch block with short PR interval” in healthy young people prone to paroxysmal tachycardia and/or atrial fibrillation in the landmark paper by Drs. Wolff, Parkinson, and White in 1930. WPW syndrome now represents patients with the abnormal ECG pattern (short PR interval with delta wave – see Figure 1) with episodes of supraventricular tachycardia (SVT). The delta wave represents an accessory pathway located along the atrioventricular groove or the septal region outside the AV node. This accessory pathway, together with the AV node can support an atrioventricular reentrant tachycardia. Asymptomatic WPW, or isolated ventricular preexcitation, is used to describe patients with an abnormal ECG pattern without any cardiovascular symptoms.  

 

Natural history of WPW

 The prevalence of WPW syndrome in childhood is estimated to be 0.4-2.2 per 1,000 individuals and is more common among males.[2] First-degree relatives of symptomatic WPW patients have an increased risk of preexcitation, estimated to be 5.5 per 1,000. The majority of patients with WPW syndrome have normal cardiac anatomy. However, associated structural heart disease is present in some patients, most commonly Ebstein’s anomaly, hypertrophic cardiomyopathy and congenitally corrected transposition of the great arteries. 

In patients with ventricular preexcitation, about 20%-30% will develop episodes of SVT,[2] with peaks in infancy and the second decade of life. In infants with WPW syndrome, SVT often becomes less frequent over the first year of life (in >90% patients). In the first year of life, the accessory connection loses anterograde conduction in as many as 40% of patients. If SVT and WPW persist beyond 5 years of age, they continue to be present more than a decade later in >75% of patients.[3] 

Arrhythmias: Mechanisms

The different types of arrhythmias associated with WPW are summarized in Table 1.

The most common mechanism of SVT associated with an accessory pathway is atrioventricular reentrant tachycardia (AVRT) which utilizes the AV node in the anterograde direction and the accessory pathway in the retrograde direction from the ventricle to the atrium. This is referred to as orthodromic reciprocating tachycardia (ORT – see Figure 2), accounting for over 75% of episodes of SVT utilizing accessory pathways. 

Approximately 3%-10% of SVT utilize the accessory pathway in an anterograde direction from atrium to ventricle and SVT ECG shows a preexcited or wide QRS complex during tachycardia, termed antidromic reciprocating tachycardia (ART – Figure 3). Children with ART are more likely to have short accessory pathway effective refractory period (APERP) and multiple accessory pathways. 

WPW patients are at risk for atrial fibrillation (AF). AF is rare in childhood but the lifetime incidence of AF with WPW ranges from 8%-18%, and increases with advancing age. Clinical episodes of AF occur in less than 5% of children and AF is very rare in children in the absence of WPW. Atrial fibrillation with rapid anterograde conduction (Figure 4) over the accessory pathway poses a risk of triggering ventricular fibrillation (VF) and sudden death. 

The incidence of ventricular fibrillation (VF) in patients with preexcitation is variously estimated to be 0.32%-1.4%.[4] The risk of sudden cardiac death is estimated to be less than 0.15% per year.[4] Although syncope or aborted sudden death is an uncommon presentation, it may be the first presentation of WPW, particularly in young patients, where almost 50% had no prior cardiac symptoms. 

Given the concern for the risk of sudden death in asymptomatic young patients with a WPW ECG pattern, the Pediatric and Congenital Electrophysiology Society (PACES) and Heart Rhythm Society (HRS) developed a consensus statement on the evaluation and management of these patients, published in June 2012.[1] See the Management Algorithm in Table 2 for a summary of PACES/HRS recommendations. 

Risk stratification in asymptomatic WPW patients

The purpose of risk stratification in asymptomatic WPW patients is to identify those at risk for sudden cardiac death due to lethal cardiac arrhythmias. Patients identified to be at high risk can be offered catheter ablation as a potential curative procedure. Since catheter ablation carries inherent procedural risks, risk stratification will weigh the risk-to-benefit ratio of an intracardiac electrophysiology (EP) study and catheter ablation. 

Athletes with asymptomatic WPW diagnosed during athletic screening are an important subgroup of patients to consider. The 2005 task force for arrhythmia[3] advised that selected asymptomatic athletes who anticipate moderate or high level activity undergo electrophysiology study to determine certain technical EP criteria which may not be useful for the general pediatrician but form the basis for advanced risk stratification. EP study is performed to determine: 

1. anterograde accessory pathway effective refractory period (APERP) cycle length (in milliseconds, msec) at which the accessory pathway fails to conduct anterograde when the atrium is paced rapidly 

2. shortest interval between preexcited complexes in atrial fibrillation 

3. number of accessory connections 

Catheter ablation is recommended for patients with multiple accessory connections, or when accessory pathway can conduct at rates exceeding 240 bpm.[2] 

 

Noninvasive testing

Noninvasive testing (ECG, 24-hour Holter, and exercise stress test) is used to establish the true loss of ventricular preexcitation at physiological heart rates. Abrupt and clear loss of delta waves with exercise suggests that the accessory pathway cannot conduct rapidly. The limitation of noninvasive testing is that it may be difficult to clearly demonstrate absolute loss of ventricular preexcitation and correlation with low risk is not perfect. 

 

ECG and Holter

The “true” assessment of the anterograde conduction properties of the accessory pathway is seen in ECG obtained during atrial fibrillation with preexcitation. The shortest preexcited RR interval (SPERRI) has been used to determine accessory connection properties. A SPERRI of 220-250 msec, and especially <220 msec is more commonly seen in patients with WPW who have experienced cardiac arrest.[5] Intermittent ventricular preexcitation suggests poor anterograde conduction through the accessory connection (Figure 5). Patients with intermittent ventricular preexcitation are still at risk for developing SVT. In a retrospective analysis of a large group of military aviators with WPW followed over 20 years, 23% of asymptomatic WPW patients with constant preexcitation developed reentrant SVT in comparison to the 8.3% of those who only exhibited intermittent preexcitation in follow-up. 

The presence of multiple accessory connections has been identified as a risk factor for ventricular fibrillation.[5,6] Multiple accessory connections may present as different preexcited morphologies on an ECG or Holter monitoring and these patients are less likely to remain asymptomatic.[7] Serial Holter monitoring in asymptomatic WPW patients may be used to screen for paroxysmal atrial fibrillation. 

  

Exercise testing

 Abrupt and clear loss of ventricular preexcitation (delta wave) during exercise confirms a long anterograde accessory pathway effective refractory period (APERP). However, more commonly, there is only gradual loss of ventricular preexcitation. Change in delta wave appearance during exercise testing is dependent upon the relative effects of sympathetic stimulation on AV nodal conduction and anterograde conduction down the accessory pathway. Enhanced AV nodal conduction with exertion may obscure the persistent preexcitation, especially via a left-sided accessory pathway. In one study in adults, persistence of ventricular preexcitation during exercise testing had a sensitivity of 96%, but a specificity of only 17% in predicting either a SPERRI in AF ≤250 msec or an APERP of ≤250 msec. 

If there is no clear and abrupt loss of preexcitation seen in noninvasive testing to suggest low risk characteristics, then invasive testing should be considered. 

  

Invasive testing

 Invasive EP testing includes transesophageal pacing (TEP) study and intracardiac EP study. The purpose of invasive testing in asymptomatic WPW patients is to identify the subgroup of patients who have accessory pathways with rapid anterograde conduction, and who therefore may develop atrial fibrillation with rapid ventricular response leading to ventricular fibrillation and sudden death. The benefits of catheter ablation in these patients may outweigh the risks associated with the procedure. There are several parameters measured during invasive testing: SPERRI during AF, APERP, and inducibility of AV reciprocating tachycardia with and without the beta-agonist, isoproterenol. 

  

Transesophageal pacing (TEP) study

 The anterograde accessory pathway characteristics obtained by TEP study correlate well with intracardiac EP study. However, TEP may be difficult to perform in older children, is less effective to diagnose presence of multiple accessory pathways, cannot precisely localize the accessory pathway and cannot assess the retrograde conduction of the pathway. 

  

Intracardiac EP study

 Intracardiac EP study is the definitive technique for evaluation of clinical intracardiac conduction. It allows evaluation of the characteristics of the accessory pathway. In contrast to TEP study, intracardiac EP study allows localization of the accessory pathway(s), and allows assessment of retrograde conduction of the pathway(s). Review of clinical and invasive EP data by Santinelli[7] from 184 asymptomatic children with WPW with a median follow-up of 5 years showed significantly different EP characteristics in patients who later became clinically symptomatic when compared to those who remained asymptomatic: APERP ≤240 msec (49% vs 17%), multiple accessory pathways (47% vs 6%), and intact retrograde conduction up the accessory pathway at baseline (84% vs 26%). Furthermore, if counseling was done prior to the intracardiac EP study, it is possible to proceed with catheter ablation and potentially eliminate the accessory pathway under the same procedure. EP parameters indicating low risk accessory pathways from noninvasive and invasive testing are summarized in Table 3. 

 

Catheter ablation success rates and risks

Catheter ablation in pediatric patients was first introduced in 1990. Since then, radiofrequency ablation has become generally accepted as a therapy for WPW due to high success rates and a low-risk profile. The Pediatric Electrophysiology Society established the Pediatric Radiofrequency Ablation Registry and has since published Prospective Assessment of Pediatric Cardiac Ablation study (PAPCA).[8] In the PAPCA study, the overall success rate was 93% for WPW.[9] The overall recurrence rate at 1-year follow-up reported in the prospective study was 11.3%, with most of the recurrences during the first 2 months following the ablation procedure.[8] 

Serious adverse events related to catheter ablation are AV block, cardiac perforation, coronary artery injury and thromboembolic events. The PAPCA study reported a complication rate of 4% and there were no deaths.[9] AV block occurred in 0.9% of WPW patients, but only in those with a pathway near the AV node. Injury to the right coronary artery was reported in young pigs where radiofrequency ablation lesions were delivered along the right AV groove. The reported incidence of coronary artery injury is 0.8%-1.3%. Acute coronary injury is more commonly noted in the posteroseptal region. The highest incidence of coronary injury was reported in patients with congenital heart disease, specifically Ebstein’s anomaly of the tricuspid valve. Thromboembolic events have been reported to occur in 0.2%-0.8% of procedures. The risk of thromboembolic events was not eliminated by anticoagulation protocols, the number of RF lesions, or mode of temperature-controlled ablation. Catheter ablation for WPW is summarized in Table 4. 

  

Other considerations

Catheter ablation in young children: WPW syndrome in infancy can usually be medically managed and SVT tends to become less frequent after the first few months of life. However, catheter ablation may need to be considered in young patients with medically refractory arrhythmias, complex substrates (multiple accessory pathways and/or congenital heart disease), and severe symptoms. Success rates are comparable to those seen in older children, but the rates of adverse events may be higher.[10] Complications during radiofrequency ablation in small children may be related to RF energy dose, lesion number and total application time, indexed for body size. 

Asymptomatic WPW and ADHD: Attention deficit hyperactivity disorder (ADHD) is the most common neurobehavioral disorder in childhood and stimulant medications are an important treatment modality. ADHD medications increase the heart rate on average 1-2 bpm and the systolic blood pressure 3-4 mmHg. The reported rates of sudden death in patients taking ADHD medications identified by the FDA Adverse Event Reporting System from 1992-2004 are less than the background rates of sudden death reported in the literature. Although there are theoretical concerns about using ADHD medications in patients with WPW, there is no definitive evidence to date to support increased cardiac events. Patients with asymptomatic WPW may receive ADHD medications with close observation for development of symptoms.[1] 

WPW and sports participation: According to the 36th Bethesda Conference Task Force on Arrhythmias,[3] risk stratification with an EP study is advisable in asymptomatic athletes engaged in moderate- to high-level competitive sports. The European Society of Cardiology has a more aggressive statement mandating that all athletes with WPW undergo comprehensive risk assessment including an EP study. Despite the differences between the European and American cardiology societies’ recommendations in the management of asymptomatic athletes with ventricular preexcitation on ECG, young athletes once diagnosed should be referred to a pediatric electrophysiologist for risk stratification. 

  

Conclusion

If a patient has asymptomatic WPW, noninvasive testing with ECG, 24-hour Holter, and exercise stress test can be used to assess low risk characteristics. Asymptomatic WPW patients should be referred for further evaluation and counseling if noninvasive testing shows persistent WPW. 

  

References

 [1.] Cohen MI, Triedman JK, Cannon BC, et al. PACES/HRS Expert consensus statement on the management of the asymptomatic young patient with a Wolff-Parkinson-White (WPW, ventricular preexcitation) electrocardiographic pattern. Heart Rhythm 2012;9:1006-1024. 

[2.] Pappone C, Santinelli V, Rosanio S, et al. Usefulness of invasive electrophysiologic testing to stratify the risk of arrhythmic events in asymptomatic patients with Wolff-Parkinson-White pattern: results from a large prospective long-term follow-up study. J Am Coll Cardiol 2003;41:239-244. 

[3.] Zipes DP, Ackerman MJ, Estes NA 3rd, et al. 36th Bethesda Conference. Task Force 7: arrhythmias. JACC 2005;45:1354-1363. 

[4.] Pappone C, Vicedomini G, Manguso F, et al. Risk of malignant arrhythmias in initially symptomatic patients with Wolff-Parkinson-White syndrome: results of a prospective long-term electrophysiological follow-up study. Circulation 2012;125:661-668. 

[5.] Santinelli V, Radinovic A, Manguso F, et al. Asymptomatic ventricular preexcitation: a long-term prospective follow-up study of 293 adult patients. Circ Arrhythm Electrophysiol 2009;2:102-107. 

[6.] Pappone C, Manguso F, Santinelli R, et al. Radiofrequency ablation in children with asymptomatic Wolff-Parkinson-White syndrome. NEJM 2004;351:1197-1205. 

[7.] Santinelli V, Radinovic A, Manguso F, et al. The natural history of asymptomatic ventricular pre-excitation. A long-term prospective follow-up study of 184 asymptomatic children. JACC 2009;53(3):275-280. 

[8.] Van Hare GF, Javitz H, Carmelli D, et al. Prospective assessment after pediatric cardiac ablation: recurrence at 1 year after initially successful ablation of supraventricular tachycardia. Heart Rhythm 2004;1:188-196. 

[9.] Van Hare GF, Javitz H, Carmelli D, et al. Prospective assessment after pediatric cardiac ablations: demographics, medical profiles, and initial outcomes. J Cardiovasc Electrophysiol 2004;15:759-770. 

[10.] Kugler JD, Danford DA, Deal BJ, et al. Radiofrequency catheter ablation for tachyarrhythmias in children and adolescents. NEJM 1994;330:1481-1487. 

  

For Further Reading

 [1.] Wolff L, Parkinson J, White P. Bundle-branch block with short P-R interval in healthy young people prone to paroxysmal tachycardia. AHJ 1930;5(6):685-704. 

[2.] Munger TM, Packer DL, Hammill SC, et al. A population study of the natural history of Wolff-Parkinson-White syndrome in Olmsted County, Minnesota, 1953-1989. Circulation 1993;87:866-873. 

[3.] Swiderski J, Lees MH, Nadas AS. The Wolff-Parkinson-White syndrome in infancy and childhood. Br Heart J 1962;24:561-580. 

[4.] Vidaillet HJ Jr, Pressley JC, Henke E, et al. Familial occurrence of accessory atrioventricular pathways (preexcitation syndrome). N Engl J Med 1987;31:65-69. 

[5.] Sarubbi B, D’Alto M, Vergara P, et al. Electrophysiological evaluation of asymptomatic ventricular preexcitation in children and adolescents. Int J Cardiol 2005;98:207-214. 

[6.] Montoya PT, Brugada P, Smeets J, et al. Ventricular fibrillation in the Wolff-Parkinson-White syndrome. Eur Heart J 1991;12:144-150. 

[7.] Bricker JT, Porter CJ, Garson A Jr, et al. Exercise testing in children with Wolff-Parkinson-White syndrome. Am J Cardiol 1985;55(8):1001-1004. 

[8.] Fitzsimmons PJ, McWhirter PD, Peterson DW, et al. The natural history of Wolff-Parkinson-White syndrome in 228 military aviators: a long-term follow-up of 22 years. AHJ 2001;142:530-536. 

[9.] Gaita F, Giustetto C, Riccardi R, et al. Stress and pharmacologic tests as methods to identify patients with Wolff-Parkinson-White syndrome at risk of sudden death. AJC 1989;64(1):487-490. 

[10.] Corrado D, Pelliccia A, Bjornstad HH, et al. Cardiovascular pre-participation screening of young competitive athletes for prevention of sudden death: proposal for a common European protocol. Conensus Statement of the Study Group of Sport Cardiology and the Working Group of Myocardial and Pericardial Diseases of the European Society of Cardiology. Eur Heart J 2005;26:516-524. 

 

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