Reverse use-dependent effects of sotalol demonstrated by recording monophasic action potentials of the right ventricle

Abstract

In 22 patients referred for electrophysiologic study, monophasic action potentials (MAP) were recorded from the right ventricular aspect of the ventricular septum. The duration of MAP at 90% (MAP 90) and 30% (MAP 30) repolarization was measured in sinus rhythm, at a constant atrial paced cycle length of 600 ms for 3 minutes and at constant ventricular paced cycle lengths of 600, 500, 400 and 300 ms for 20 beats. Programmed ventricular stimulation from the apex of the right ventricle was performed at a basic drive cycle length of 400 ms and MAP 90 and MAP 30 of premature beats was determined. Changes of MAP duration were assessed 20 minutes after administration of intravenous sotalol 1.5 mg/kg. Sotalol significantly increased MAP 90 and MAP 30 in sinus rhythm. This was independent from sinus cycle length prolongation as evidenced by a significant prolongation of MAP 90 and MAP 30 with constant atrial pacing after sotalol. With slow ventricular stimulation frequencies and with long coupling intervals at programmed ventricular stimulation, sotalol significantly prolonged MAP 90 and MAP 30; with high stimulation frequencies and at short coupling intervals the action potential-prolonging effect of sotalol was diminished, indicating a reverse use-dependent effect of sotalol on repolarization of the right ventricle in humans.