Effect of propafenone in the Wolff-Parkinson-White syndrome: electrophysiologic findings and long-term follow-up.

The electrophysiologic and long-term efficacy of propafenone, a relatively new antiarrhythmic agent, was assessed in 47 patients with accessory pathways. In 23 patients (group I), the electrophysiologic effects were assessed initially. In 19 patients in this group and in 24 additional patients (group II), long-term therapy with oral propafenone was initiated. The mean age of the patients was 38 years in group I and 41 years in group II. The duration of a history of tachycardia in both groups was 12 years (mean); 14 patients previously had had attacks of syncope. During the electrophysiologic study in group I, propafenone did not change the spontaneous sinus rate. Corrected sinus node recovery time as well as the AH interval, HV time, QRS duration and effective refractory periods of the atria and ventricles was significantly prolonged. The effective refractory period of the accessory pathway increased from 238 to 322 ms (p less than 0.02). The 1:1 conduction capacity of the accessory pathway decreased from 231 to 176 beats/min (mean; p less than 0.01). Complete block in the anterograde direction occurred in 6 patients. The shortest RR interval during atrial fibrillation increased from 232 to 303 ms (p less than 0.05). The retrograde refractory period of the accessory pathway was prolonged from 245 to 295 ms (p less than 0.01). Complete or 2:1 retrograde block during basic drive occurred in 3 patients and 1 patient, respectively. In 6 of 15 patients, propafenone made sustained supraventricular tachycardia (SVT) either no longer inducible or nonsustained. The cycle length of induced SVT increased from 324 to 395 ms (p less than 0.01). During long-term administration (follow-up duration 2 to 3 years), 17 of 43 patients did not report any episode of symptomatic tachycardia. In another 18 patients, tachycardia was rare, slower and self-terminating. In only 3 patients, the frequency and severity of attacks had not changed. One patient with dilated cardiomyopathy died suddenly. Side effects necessitating discontinuation of medication were observed in only 2 patients. The remaining side effects, if present, were tolerated, and dosage dependent. In conclusion, propafenone is an effective and well-tolerated antiarrhythmic agent in the long-term management of patients with the Wolff-Parkinson-White syndrome.