[Electrophysiological properties of atrial fibrillation with WPW syndrome and the role of procainamide in conversion].

Fifty one patients with recurrent episodes of atrial fibrillation associated with WPW syndrome were studied by pre-operative clinical electrophysiogical testing. The results showed that: these patients had an markedly prolonged intra-atrial conduction time (PA intervals: 42.22 +/- 10.93 ms) than the patients only with attack of atrioventricular reentry tachycardia (AVRT) (PA intervals: 17.21 +/- 9.68ms, P less than 0.001). The attack of atrial fibrillation related to an markedly prolonged atrial vulnerable phase and the retrograde conduction of accessory pathway (AP). The clinical results of atrial fibrillation were decided by the antegrade effective refractory period (AERP) of AP. When the shortest R-R (V-V) intervals during attack of atrial fibrillation was shorter than 180ms, the atrial fibrillation spontaneously turned to the ventricular fibrillation. The conversion of atrial fibrillation to sinus rhythm showed that procainamide not only prolonged AERP of AP, which were 248.57 +/- 15.74ms and 388.57 +/- 63.9 ms (P less than 0.001) respectively before and after intravenous procainamide infusion, but also prolonged intra-atrial conduction time significantly, the PA interval before and after intravenous procainamide infusion were 42.22 +/- 10.93 ms and 57.14 +/- 11.12 ms (P less than 0.025) respectively.