Electrophysiology and long-term efficacy of pentisomide in patients with supraventricular tachycardia.

The electrophysiologic effects of pentisomide were investigated after intravenous (5 mg/kg) and oral (900-1200 mg three times a day) application in 9 patients with drug refractory atrioventricular nodal tachycardia and 6 patients with orthodromic atrioventricular re-entrant tachycardia. Pentisomide did not change sinus cycle length, effective refractory period of the right ventricle and the atrioventricular node. AH, HV interval, effective refractory period of the right atrium, QRS duration and QTc duration were (p less than or equal to 0.01) increased. Tachycardia cycle length was only increased after intravenous application of pentisomide, antegrade effective refractory periods of the accessory pathways and shortest fully pre-excited R-R intervals during atrial fibrillation were increased after the oral treatment phase (p = 0.054). Intravenous pentisomide prevented tachycardia in 6/9 patients with atrioventricular nodal tachycardia and in 2/6 patients with atrioventricular re-entrant tachycardia. If intravenous pentisomide did not prevent induction of the tachycardia, oral pentisomide was not effective either. During long-term follow-up 2/7 patients with atrioventricular nodal tachycardia and 1/4 patient with atrioventricular re-entrant tachycardia had a recurrence. Long-term treatment with pentisomide had to be discontinued because of possible side effects in 2 patients. It is concluded, that the electrophysiological effects of pentisomide are similar to those of flecainide and propafenone.