Abstract
Summary
The effects of N-acetylprocainamide (NAPA) and procainamide (PA) on myocardial force of contraction were compared in open-chest, vagotomized, pentobarbital-anesthetized dogs, with the use of a Walton-Brodie strain gauge sutured to the right ventricle. NAPA increased myocardial force of contraction, particularly at the high dose level (40 mg/kg). PA, on the other hand, had a negative inotropic effect that was equally apparent at all doses (10-40 mg/kg). In addition, both NAPA and PA had a negative chronotropic effect and caused a reduction in mean arterial pressure. The mechanisms of the inotropic and hypotensive actions of NAPA require elucidation. Some of the implications of these findings for the clinical use of NAPA as an antiarrhythmic agent are discussed.
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