Electrophysiologic Effects of Cocaine on the Canine Ventricle

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Abstract
To evaluate the electrophysiologic effects of cocaine on the ventricle, 12 conscious dogs were studied before and after a bolus and infusion of cocaine titrated to maximum tolerance or to an increase in the mean blood pressure by at least 15%. Plasma cocaine levels, blood pressure, and surface and intracardiac electrograms were recorded. Programmed electrical stimulation was per-formed from the right ventricle at drive cycle lengths of 400 and 350 ms with introduction of up to three extrastimuli. The right ventricular effective refractory period de-creased by 10% (p ≤ 0.01) and the mean blood pressure increased by 19% (p ≤ 0.01). No sustained spontaneous or induced ventricular arrhythmias were recorded after cocaine administration. There were no significant changes in pacing threshold, intraventricular conduction, heart rate, QRS or QTc intervals. The cocaine dose in-fused was 2.1 ± 1.0 mg/kg; cocaine plasma levels were 1969 ± 959 ng/ml immediately after the bolus and 508 234 ng/ml at the end of the study. It is concluded that in a presumably normal canine heart and at the doses given that cocaine decreases right ventricular effective refractory period, does not change intraventricular conduction, and does not result in sustained spontaneous or induced ventricular arrhythmias.