Editor's Note: Commentary based on Pappone C, Vicedomini G, Manguso F, et al. WPW Syndrome in the Era of Catheter Ablation: Insights from a Registry Study of 2169 Patients. Circulation 2014;130:811-9.

In patients with symptomatic Wolff-Parkinson-White (WPW) syndrome, treatment strategies are relatively defined with curative catheter ablation as the most common recommended approach. The management of asymptomatic patients is more controversial. In these patients, the primary concern is reducing risk of sudden death, ventricular arrhythmias, and atrial fibrillation (AF). Regarding malignant ventricular arrhythmia risk, short antegrade refractoriness of the accessory pathway conveys the highest risk. For example, in patients with AF, higher risk is associated with persistence of accessory pathway conduction with R-R intervals less than 250 ms. In the absence of high-risk features, cardiac arrest rates are relatively low in asymptomatic WPW patients with estimated rates <0.2%.¹

The notion of low-risk, asymptomatic WPW patients was challenged in an eight-year prospective study involving 2,169 participants from a single-center WPW registry in Italy.² Of the enrolled participants, 1,001 did not undergo radiofrequency ablation (550 were asymptomatic) and 1,168 underwent radiofrequency ablation (206 were asymptomatic). All patients underwent invasive electrophysiology testing to examine the conduction properties of the accessory pathway(s). The study confirmed the effectiveness of catheter ablation, as the procedure was successful in 98.5% of patients. However, complication rates in an experienced center were 3.9%. Fortunately most complications were temporary, but one patient developed complete heart block and three patients developed a left bundle branch block, which may impact atrioventricular conduction over time. In the group that did not undergo ablation, 15 had ventricular fibrillation (VF, 13 asymptomatic, two symptomatic) and another 78 (48 asymptomatic and 30 symptomatic) had malignant arrhythmias. Two remarkable findings were noted in VF patients: all were resuscitated with no residual neurologic sequelae and 87% of those events were children. Even in centers with excellent resuscitation programs this outcome is extraordinary and may imply the mechanisms in cardiac arrest in WPW patients are distinct from patients with structural heart disease. The VF events occurred at rest in 11 and during running in the other four. Although initially asymptomatic, all 15 had either presyncope or syncope before the arrest occurred. The most common form of malignant arrhythmias was pre-excited AF, a rhythm often felt to be a precursor to ventricular destabilization and VF. All of these patients were successfully ablated and none of the AF patients degenerated to VF. The baseline electrophysiology study data in all patients confirmed two important baseline characteristics: patients with inducible atrioventricular reentrant tachycardia that degenerates into AF and those with short antegrade refractoriness of the accessory pathway were more likely to experience VF.

This study confirms our current approach that symptomatic and asymptomatic high-risk patients, easily stratified by the electrophysiology properties of the accessory pathway, benefit from ablation. However, it also shows that catheter ablation and electrophysiology studies are not without risks. Outside of a prospective study, these data do not support broad screening for asymptomatic WPW to lower risk of cardiac arrest in the community.

The study also demonstrates that close follow-up of asymptomatic patients is warranted as high-risk patients often develop symptoms that herald adverse arrhythmia events. Unfortunately symptoms alone for monitoring are insufficient as a few of these patients only developed them immediately before the development of VF.

Why all the patients that experienced VF survived without sequelae, despite nearly half of the events occurring outside the hospital, requires further study into the mechanisms of progression and maintenance of cardiac instability in WPW syndrome. It may be that the number of events was too low to provide comparative understanding with other cardiac arrest populations. However, it is also plausible that arrest mechanisms in WPW syndrome are distinct.

Competitive athletes have traditionally been considered a higher risk group with WPW and as a consequence even if asymptomatic additional electrophysiology testing is often advocated.³ This recommendation in asymptomatic individuals heralds from the observation that most events occur during exercise or emotional stress.⁴ The Italian registry challenges the notion that most VF events occur with exercise. However, even in this registry, exertion-related events remain high at 36%. If a conservative approach is undertaken in an asymptomatic individual a treadmill exercise test can be used to look at the heart rate at which antegrade conduction block of the accessory pathway develops. Although this cannot fully mimic the physical and emotional stress of competitive athletics that influence accessory pathway conduction, the test can help identify lower risk pathways that tend to block during the exercise test.

References

1. Obeyesekere MN, Leong-Sit P, Massel D, et al. Risk of arrhythmia and sudden death in patients with asymptomatic preexcitation: a meta-analysis. Circulation 2012;125:2308-15.
2. Pappone C, Vicedomini G, Manguso F, et al. WPW syndrome in the era of catheter ablation: insights from a registry study of 2169 patients. Circulation 2014;130:811-9.
3. Heidbüchel H, Panhuyzen-Goedkoop N, Corrado D, et al. Recommendations for participation in leisure-time physical activity and competitive sports in patients with arrhythmias and potentially arrhythmogenic conditions. Part I: supraventricular arrhythmias and pacemakers. Eur J Cardiovasc Prev Rehabil 2006;13:475-84.
4. Timmermans C, Smeets JL, Rodriguez LM, Vrouchos G, van den Dool A, Wellens HJ. Aborted sudden death in the Wolff-Parkinson-White syndrome. Am J Cardiol 1995;76:492-4.

Keywords: Accessory Atrioventricular Bundle, Arrhythmias, Cardiac, Athletes, Atrial Fibrillation, Bundle-Branch Block, Catheter Ablation, Death, Sudden, Electrophysiology, Exercise Test, Heart Arrest, Heart Conduction System, Heart Rate, Physical Exertion, Pre-Excitation Syndromes, Prospective Studies, Registries, Resuscitation, Running, Sports, Stress, Psychological, Syncope, Tachycardia, Ventricular Fibrillation, Wolff-Parkinson-White Syndrome

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