Free fatty acids and the electrophysiology of the dog heart in situ: effects of isoprenaline, nicotinic acid and lipid emulsion with heparin

Abstract

Summary. The study was carried out to examine whether high plasma concentrations of free fatty acids (FFA) alone have cardiac electrophysiological effects, and whether the electrophysiological effects of isoprenaline are dependent on elevated plasma FFA. Experiments were performed in sixteen intact, healthy, pentobarbital anaesthetized dogs. Atrial, atrioventricular nodal and ventricular conduction times and refractoriness, and sinus node function were studied by His bundle electrography combined with programmed electrical stimulation. Elevation of plasma FFA by Intralipid and heparin from a median value of 363 to 1780 u‐moM‐1 did not induce any changes in cardiac electrophysiology. Intravenous infusion of isoprenaline (0.15 μg‐min_1‐kg‐1) increased median plasma FFA from 410 to 2254 μmol‐l‐1. This rise in plasma FFA could be prevented by administration of nicotinic acid. The electrophysiological effects of isoprenaline were similar before and after inhibition of lipolysis. The study indicates that the cardiac electrophysiological effects of isoprenaline in the intact, healthy heart are independent of changes in plasma FFA concentrations.