THERAPY AND PREVENTION Atrial fibrillation in patients with Wolff-Parkinson- White syndrome: incidence after surgical ablation of the accessory pathway

The effect of surgical ablation of atrioventricular accessory pathways on the incidence of atrial fibrillation in patients with Wolff-Parkinson-White syndrome was examined and the results of preoperative electrophysiologic testing were studied to determine factors predictive of outcome. Among 50 consecutive surgical cases, 19 patients were identified with a past history of at least one episode of spontaneous atrial fibrillation documented by electrocardiogram before surgery. The mean number of episodes of atrial fibrillation was 1.97/patient/year during a mean symptomatic period of 6.9 years before surgery. These patients were compared with 19 consecutive patients undergoing surgery during the same time period who had a history of only reciprocating tachycardia. Patients with atrial fibrillation had a significantly shorter antegrade accessory pathway effective refractory period (270 + 39 vs 330 + 107 msec; p < .05) and much faster ventricular rates during induced atrial fibrillation (shortest RR interval 219 + 73 vs 294 + 60 msec, p < .005; average RR interval 324 + 109 vs 405 + 127 msec, p < .01). Patients with atrial fibrillation also had longer PA intervals (47 13 vs 37 + 7 msec; p < .02). At preoperative electrophysiologic testing, 18 patients with atrial fibrillation had atrial fibrillation induced and 14 sustained the arrhythmia for longer than 10 min. In contrast, atrial fibrillation, although induced in 14 of 19 patients with reciprocating tachycardia, was not sustained in any. Thus electrophysiologic testing suggested that both accessory pathway properties and atrial vulnerability may predispose to atrial fibrillation. There were five episodes of atrial fibrillation in three patients (0.3/patient) during the first month after surgery. During a mean follow-up of 1.9 years, only one patient with an associated cardiomyopathy has had recurrent atrial fibrillation. We conclude that surgical ablation of the accessory pathway in patients without organic heart disease prevents further atrial fibrillation. This suggests that reciprocating tachycardia or ectopy mediated by the accessory pathway is the mechanism of induction of spontaneous atrial fibrillation in the majority of patients with Wolff-Parkinson-White syndrome. Circulation 72, No. 1, 161-169, 1985. ATRIAL FIBRILLATION occurring in patients with Wolff-Parkinson-White syndrome is a potentially lifethreatening arrhythmia because it may lead to ventricular fibrillation.' Accordingly, the pathogenesis of atrial fibrillation in these patients has been the subject of a number of investigations. Electrophysiologic testing of patients has revealed that atrioventricular (AV) reciprocating tachycardia can be induced in the majority of patients who have a past history of atrial fibrillaFrom the Clinical Electrophysiology Laboratory, University Hospital, University of Western Ontario, London, Ontario. This work was supported by grants from the Ontario Heart Foundation and the Ontario Ministry of Health. Address for correspndence: A. D. Sharma, M. D_, University Hospital, Box 5339, Station A, London, Ontario, Canada N6A 5A5. Received Dec. 19, 1984; revision accepted April 11, 1985. Presented in part to the Canadian Cardiovascular Society, October 1984. tion.2 -1 Furthermore, the spontaneous degeneration of AV reciprocating tachycardia to atrial fibrillation has been observed during electrophysiologic testing.'.6 These findings suggest that atrial fibrillation can occur secondary to AV reentry by means of the accessory pathway and that the accessory pathway directly participates in the induction of atrial fibrillation. However, only a minority of patients with a past history of atrial fibrillation are observed to have spontaneous degeneration of AV reciprocating tachycardia to atrial fibrillation during electrophysiologic testing. 4 In patients in whom extrastimulus techniques have been required to induce atrial fibrillation,' 7 8 the induction of atrial fibrillation by a single extrastimulus has suggested primary atrial vulnerability to fibrillation.7 In these patients the accessory pathway would not be an obligatory link in the initiation of atrial fibrilVol. 72, No. I, July 1985 161 by gest on July 5, 2017 http://ciajournals.org/ D ow nladed from