DEPENDENCY ON ATRIAL ELECTROPHYSIOLOGICAL PROPERTIES OF APPEARANCE OFPAROXYSMAL ATRIAL-FIBRILLATION IN PATIENTS WITH WOLFF-PARKINSON-WHITE-SYNDROME - EVIDENCE FROM ATRIAL VULNERABILITY BEFORE AND AFTER RADIOFREQUENCY CATHETER ABLATION AND SURGICAL CRYOABLATION

The pathogenesis of paroxysmal atrial fibrillation in patients with Wo lff-Parkinson-White syndrome and the effects of elimination of accesso ry pathways on the appearance of atrial fibrillation are still controv ersial. Fifty-four patients with Wolff-Parkinson-White syndrome were c lassified into three groups: a No AF group (n = 24), patients without paroxysmal atrial fibrillation; an RF-AF Group (n = 12), patients with paroxysmal atrial fibrillation whose accessory path ways were elimina ted using radiofrequency catheter ablation; and a Cryo-AF Group (n = 1 8), patients with paroxysmal atrial fibrillation whose accessory pathw ays were eliminated with surgical cryoablation. The electrophysiologic al characteristics of each group were evaluated prior to and following the elimination of their accessory path ways. As indices of atrial vu lnerability, the presence of fragmented atrial activity and repetitive atrial firing zones were assessed, Inducibility of atrial fibrillatio n was significantly reduced following ablation of accessory pathways i n the Cryo-AF group (83.3%-5.6%, P < 0.0001), while it was unchanged i n the RF-AF group (83.3%-75%). In preablation studies, the effective r efractory periods of the atrium in the RF-AF group and the Cryo-AF gro up was significantly shorter compared with the No AI; group (204 +/- 1 8 ms, 197 +/- 16 ms vs 246 +/- 44 ms, respectively, P < 0.0001). Follo wing ablation, the effective refractory period for patients in the Cry o-AF group was significantly prolonged compared with before ablation ( 197 +/- 16 ms to 232 +/- 24 ms, P < 0.0001). As a result of this prolo ngation of the effective refractory period of the atrium, the fragment ed atrial activity and repetitive atrial response zones narrowed follo wing ablation in the Cryo-AF group, but not in the RF-AF group. Theref ore, the pathogenesis of atrial fibrillation in patients with Wolff-Pa rkinson-White syndrome may depend on the refractory period of the atri um rather than on the presence of accessory pathways.