Editor’s Note:  This article is based on 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;125:661-8.

Summary

This is a single center observational study of patients with symptomatic Wolff-Parkinson-White (WPW) syndrome who, after invasive electrophysiological evaluation, did not undergo catheter ablation for various reasons. Patients were included if they had presented after a first episode of atrio-ventricular reciprocating tachycardia (AVRT) and had not undergone prior ablations or experienced a malignant arrhythmias (MA). The purpose of the study was to define risk factors and predictors of MA in this cohort during longitudinal follow up.

Methods

The present cohort was chosen from a group of 8575 consecutive patients with the WPW syndrome referred to the center over a 10-year period between 1997 and 2007. Electrophysiological evaluation was performed in a standard manner and included determination of effective refractory period (ERP) of the accessory pathways (AP), shortest pre-excited cycle length (CL) during AF or atrial pacing and documentation of presence multiple pathways. It is unclear if adrenergic stimulation was utilized during the studies. The group of patients included in this study did not undergo ablation of the pathways for the following reasons: refusal on the part of the patient, had no consent obtained for ablation, or experienced anesthetic or vascular complications during the initial EP study. Patients were followed at frequent intervals for assessment of symptoms, 12 lead ECGs and 24-hour Holter monitoring. The majority (98%) was not prescribed an antiarrhythmic drug.

MA was defined as symptoms of hemodynamic instability or resuscitation from cardiac arrest.

Results

A total of 369 patients (mean age 23±12.5 years; 62% male) comprised the study group. Baseline characteristics of this group did not differ from the group that underwent ablation. AVRT (mean CL 251.4 ± 10 msec) was inducible in all patients. The mean antegrade ERP of the AP was 278.4 ± 32.2 msec. Multiple accessory pathways were documented in 3.8% of patients. 

Over a mean follow up of 42.7 ± 9.6 months, recurrent arrhythmia occurred in 201 patients (54.5%). Of these, 29 patients (7.8%) were noted to have MAs with syncope or presyncope in 25, hemodynamic collapse due to rapid pre-excited ventricular responses to AF in 3 or resuscitation from cardiac arrest due to ventricular fibrillation in 1. The rest of the 168 patients remained asymptomatic.

Compared with the patients without MAs, those who experienced MA had faster conducting pathways (antegrade ERP of accessory pathway 264.8 ± 16.7 vs. 239.7 ±14 msec, p < 0.001), a higher prevalence of multiple accessory pathways (2.9% vs. 24%, p < 0.001) and, were more likely during baseline EP study to have spontaneous degradation of induced AVRT to AF (1.2% vs. 31%, p < 0.001). In multivariate analysis, antegrade ERP of AP and spontaneous degradation of AVRT to AF correlated with occurrence of MAs.

Conclusion

Symptomatic patients with WPW syndrome have a low incidence of malignant arrhythmias and electrophysiological predictors of adverse outcomes are similar to those described in the past for asymptomatic patients.

Perspective

A major concern for clinicians dealing with patients with an ECG pattern of ventricular pre-excitation is the small but well-established risk of sudden cardiac death. Several retrospective studies have attempted to stratify risk for sudden death in the WPW syndrome. The antegrade conduction properties of the accessory pathway remain the most important risk factor. In large series of patients resuscitated from VF related to the WPW syndrome, shortest pre-excited RR interval during AF was <250 msec^(1,2). Other high-risk features identified include young age, male sex, the presence of multiple pathways, history of AF, syncope and presence of AVRTs. However, the incidence of sudden cardiac death in the WPW syndrome has been estimated to be 0.25% per year with a lifetime risk of 3-4%⁽³⁾. Given this very low event rate, any individual predictors of risk will necessarily have a low positive predictive value.

The present study is important because of the large number of symptomatic patients with known electrophysiological characteristics longitudinally followed to provide data on natural history. The majority (>90%) had benign outcomes with no symptoms or recurrence of tolerable supraventricular arrhythmias. Although MAs are described in 7.8% of patients, arrhythmia related hemodynamic collapse was documented in only 4 patients (one cardiac arrest and three with rapid pre-excited AF) accounting for a 1.1% event rate over the 40 month period of follow up. The inclusion of syncope or pre-syncope as malignant arrhythmia clouds the results of the study as these are non-specific symptoms. For example, an SVT by itself, is known to cause syncope in the presence of a high vagal tone. Hence, the exact incidence of truly malignant arrhythmias is difficult to determine from this study. Despite these limitations, the study reaffirms the relatively benign outcomes in patients with the WPW syndrome.

With catheter ablation being a common intervention in the modern era, patients seldom undergo invasive evaluation without intend to proceed to ablation therapy. The present study offers support for a strategy of EP testing without necessarily undertaking high-risk ablation such as those of pathways in locations associated with increased risk of heart block. In the absence of high-risk EP characteristics, a strategy of monitoring is associated with a low probability of adverse events.

References

1. Klein GJ, Bashore TM, Seller TD, Pritchett EL, Smith WM, Gallagher JJ. Ventricular fibrillation in the Wolff-Parkinson-White syndrome. New England J Med 1979; 301:1080-1085.
2. Timmermans C,  Smeets LRMJ, Rodriquez L, Vrouchos G, Dool A, Wellens HJJ. Aborted sudden death in the Wolff-Parkinson-White syndrome. Am J Cardiol 1995; 76:492-494.
3. Munger TM, Packer DL, Hammil SC, et al. A population study of the natural history of Wolff-Parkinson-White syndrome in Olmsted Country, Minnesota. Circulation 1993; 87:866-873.

Clinical Topics: Arrhythmias and Clinical EP, Congenital Heart Disease and Pediatric Cardiology, Implantable Devices, EP Basic Science, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Congenital Heart Disease, CHD and Pediatrics and Arrhythmias

Keywords: Catheter Ablation, Heart Block, Resuscitation, Syncope, Ventricular Fibrillation, Wolff-Parkinson-White Syndrome

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