Risk of Arrhythmic Events in Asymptomatic Patients with Wolff-Parkinson-White Pattern

Abstract & Commentary

Synopsis: In asymptomatic patients with preexcitation, electrophysiologic testing can stratify the risk of future symptomatic and fatal arrhythmic events.

Source: Pappone C, et al. J Am Coll Cardiol. 2003;41: 239-244.

Pappone and colleagues from milan, italy, report a prospective study on the natural history of asymptomatic patients with preexcitation. Pappone et al recruited 212 patients with asymptomatic preexcitation who had been discovered during a routine examination that was not performed because of symptoms. The age of enrollment ranged from 7 to 63 years with a mean age of 35.8 (± 20.5) years. Patients underwent an initial electrophysiologic study, which characterized the properties of the accessory pathway, the site(s) and number of accessory pathways present, and the ability to induce both atrioventricular reciprocating tachycardia (AVRT) and atrial fibrillation (AF). Patients were not specifically treated for arrhythmias. Patients were followed clinically off antiarrhythmic drugs after the baseline electrophysiologic study. Five years later, or earlier if symptoms or arrhythmias occurred, a second electrophysiologic study was performed.

Of the 212 original patients, 3 were lost to follow-up and 47 patients who remained asymptomatic refused repeat electrophysiologic study after 5 years. There were therefore 162 patients who completed the follow-up period and provided full data for this report. At initial study, 115 (71%) of the 162 patients had no inducible arrhythmia at the baseline study and 47 (29%) did have an inducible arrhythmia. Among the latter patients, 17 had nonsustained AF, 19 had sustained AVRT, and 11 had AVRT that degenerated into preexcited AF. Multiple accessory pathways or accessory pathway insertion sites were noted in 17 of the 212 patients (8%). The presence of multiple accessory pathways was strongly correlated (93%) with ability to induce arrhythmia. Among these 162 patients who had baseline and follow-up studies, 21 (13%) showed loss of all anterograde preexcitation on their surface ECG after 5 years. Retrograde conduction over the accessory pathway was lost in 35 of 115 patients who had no inducible arrhythmia at baseline but was never lost in those with inducible AVRT.

During 38 ± 16 months of follow-up, 33 of 162 patients (20%) became symptomatic due to arrhythmia. AVRT was noted in 25 patients and AF in 8 others. Among the 8 patients with AF during follow-up, 2 had aborted sudden death with documented ventricular fibrillation and 1 died suddenly with ventricular fibrillation. Patients who became symptomatic had a shorter anterograde effective refractory period of the accessory pathway and most, 29 of these 33 (87.8%), had manifest an inducible sustained AVRT at the baseline study. None of the 17 patients with only inducible nonsustained AF developed symptoms. Among the patients who did not have an inducible arrhythmia at the baseline study, only 4 of 115 ever developed symptoms with arrhythmia.

The 3 patients who developed VF during follow-up all had 2 accessory pathways and had also developed symptoms (palpitations) before their episode of VF. Pappone et al examined electrophysiologic and clinical predictors of arrhythmia occurrence. An inducible arrhythmia at baseline study and a younger age were both significantly associated with risk of future arrhythmic events.

Pappone et al conclude that in asymptomatic patients with preexcitation, electrophysiologic testing can stratify the risk of future symptomatic and fatal arrhythmic events. Patients who are older and have no inducible arrhythmia are at very low risk for arrhythmic events up to 5 years follow-up. Patients who are younger and have an inducible arrhythmia, particularly if they have multiple accessory pathways, are at higher risk.

They suggest that these data should be used to guide the use of electrophysiologic studies in asymptomatic patients with preexcitation.

Comment by John DiMarco, MD, PhD

The prevalence of preexcitation has been estimated to be 1-2 per 1000. Many of these patients come to medical attention when they have an electrocardiogram taken for some other reason and an incidental finding of preexcitation is made. This paper by Pappone et al, which focuses on asymptomatic individuals with preexcitation, should help us manage this clinical scenario.

There are several issues that should be addressed in dealing with asymptomatic patients with preexcitation. Although it is uncommon, sudden death can be the first manifestation of Wolff-Parkinson-White syndrome. The mechanism responsible is thought to usually be AVRT that degenerates to AF with rapid rates that then deteriorates further to ventricular fibrillation. The 3 factors that have been associated in prior studies with sudden death have been a short refractory period of the accessory pathway, either measured directly or as the shortest preexcited RR interval during AF, the ability to induce AVRT, and the presence of multiple accessory pathways. Sudden death is, however, quite rare and most adult patients, as shown here, will have a history of either symptoms or documented arrhythmias before their sudden death event. The situation in children and adolecents is less certain since these individuals rarely have an ECG in the absence of symptoms and preexcitation cannot be diagnosed after death. Similarly, AVRT that does not degenerate to atrial fibrillation can usually be tolerated by the patient; thus, evaluation and therapy can be withheld until after the initial episode. Despite this, however, many patients with preexcitation either have episodes of symptoms in which it is uncertain whether there is a relationship to arrhythmia, or they may simply wish to know their risk for future arrhythmic events. The data shown here by Pappone et al suggest that patients with either multiple accessory pathways or with inducible arrhythmias are at significant risk for future arrhythmic events.

I would interpret these data to mean that if an electrophysiologic study is performed, the electrophysiologist should, in most cases, proceed to catheter ablation in patients who either have multiple accessory pathways or have an inducible AVRT. This would be particularly true in younger patients, especially children and adolescents, who are at high risk of developing symptoms. Older patients (those older than 40 or 50) who have been truly asymptomatic would rarely require a prospective study.

Despite this recommendation, the electrophysiologist must recognize that in asymptomatic individuals it is important not to place the patient at excess risk if at all possible. Therefore, I would not favor proceeding with either a difficult anteroseptal ablation where there is risk of damaging the conduction system or with a difficult posteroseptal ablation that might require coronary venous access for a successful ablation until the patient develops symptoms and the need for such a procedure is clearly demonstrated. In an experienced laboratory, the risk of ablating either a right or left free wall pathway should be acceptable.

Dr. DiMarco is Professor of Medicine Division of Cardiology University of Virginia, Charlottesville.