ELECTROPHYSIOLOGICAL EFFECTS OF NICAINOPROL IN PATIENTS WITH PAROXYSMAL SUPRAVENTRICULAR TACHYCARDIAS

The electrophysiological effects of nicainoprol, a new class I antiarrhythmic drug, were evaluated in 29 patients with supraventricular reentrant tachycardias, due to accessory pathways in 15 and dual atrioventricular nodal pathways in 14 patients. Nicainoprol was administered intravenously as a bolus followed by continuous infusion of 1.5 mg/kg in two and of 2 mg/kg in 27 patients over one hour. Nicainoprol was given as a bolus of 1.5-2 mg/kg during sinus rhythm in 11 patients or during induced supraventricular tachycardia in 18. The drug successfully terminated the tachycardia in 17 patients due to block in the retrograde tachycardia limb in 15 and the antegrade limb in 2 patients. Prolongation of the cycle length preceded the termination in each case. In one case, the termination could not be achieved despite the administration of 3 mg/kg. The sinus cycle length, heart rate corrected QT interval as well as right atrial and right ventricular effective refractory periods remained unchanged. In contrast, the intranodal and infranodal conduction times, as well as QRS duration, were prolonged significantly. In patients with dual atrioventricular nodal pathways, there was a significant (P < 0.05) increase of the effective refractory periods of the anterograde slow pathways. The changes of the anterograde fast pathways, however, did not reach significance level. More pronounced effects were found on effective refractory periods of the retrograde pathways, which were blocked in 4 patients and significantly (P < 0.05) prolonged in the remainder. Similarly, in patients with accessory pathways the effect on the retrograde conduction was more marked with complete block in 5 patients and significant prolongation of effective refractory periods and shortest paced cycle lengths in the remainder. Antegrade block occurred in 5 patients, two of whom had short (< 250 msec) effective refractory period. It is concluded that nicainoprol is highly effective in termination of supraventricular reentrant tachycardias and prevents reinducibility in the majority of the patients. Nicainoprol was well tolerated without any relevant side effects. © 1990.