ELECTROPHYSIOLOGICAL AND ANTIARRHYTHMIC E FFECTS OF A NEW CLASS-III ANTIARRHYTHMIC DRUG NIBENTAN IN PATIENTS WITH PAROXYSMAL SUPRAVENTRICULAR TACHYARRHYTHMIAS

Electrophysiological and antiarrhythmic effects of a new class III ant iarrhythmic drug nibentan were studied during intracardiac electrophys iological testing in 22 patients with paroxysmal sypraventricular tach yarrhythmias. Intravenous bolus injection of 0,125 mg/kg pf nibentan i nduced prolongation of Q - T and corrected Q - T intervals by 21,5% an d 19,2%, respectively. Electrophysiological effects of nibentan manife sted mainly in significant prolongation of atrial and right ventricula r effective refractory periods and of functional refractory periods of atrioventricular node and His-Purkinje system by 19,7%, 16,5%, 15,6% and 27,4%, respectively. Antegrade and retrograde effective refractory periods of bundle of Kent increased by 21,8% and 23,6%, respectively. Nibentan caused moderate (by 11,3%) slowing of heart rate. The result s of the study confirmed that nibentan possessed electrophysiological properties characteristic of class III antiarrhythmic drugs. The effic acy of nibentan for suppression of reproducible by endocardial pacing supraventricular arrhythmias was high: in patients with paroxysmal ort hodromic tachycardia - 73%, in patients with paroxysmal atrioventricul ar nodal reciprocal tachycardia - 75%, in patients with paroxysmal atr ial flutter-fibrillation - 75%. No arrhythmogenic effects of the drug were registered in this group of patients.