[Effect of oral propafenon on accessory pathways of atrioventricular conduction].

Fifteen consecutive patients with accessory AV pathways comprising 12 cases of the Wolff-Parkinson-White syndrome and 3 cases with exclusively retrograde conduction diagnosed by endocavitary electrophysiological investigation were studied. 5 patients had paroxysmal atrial fibrillation and the other 10 had reciprocating orthodromic tachycardia. 12 patients underwent electrophysiological investigation to measure the refractory periods and anterograde and retrograde conduction times in sinus rhythm and induced reciprocating tachycardia treatment with oral propafenone at a dose of 900 mg/day for 3 to 6 days. The refractory periods of anterograde conduction and the conduction times were then measured using an endocavitary atrial recording electrode left in position after the initial investigation. The anterograde Wenckebach point decreased from 259 +/- 35/min to 158 +/- 13/min (p less than 0.001). The refractory periods were increased from 270 +/- 45 ms to 371 +/- 100 ms (p less than 0.05). Atrial fibrillation could only be initiated in 2 cases with a mean rate which had decreased from 258 to 130/min. Reciprocating tachycardia could only be initiated in 5 cases and then with a slower rate (average cycle length increasing from 352 +/- 52 ms to 430 +/- 41 ms). Eight of these patients continued the treatment for over one year without recurrence of their arrhythmias, confirming the long-term efficacy of propafenone in the prevention of arrhythmias complicating accessory AV conduction pathways.