EFFECTS OF VERAPAMIL ON ELECTROPHYSIOLOGIC PROPERTIES OF BLOOD SUPER-FUSED CARDIAC PURKINJE-FIBERS

  • 1 January 1980
    • journal article
    • research article
    • Vol. 213  (2) , 222-227
Abstract
Blood superfusion techniques were used to study the effects of verapamil on the body surface ECG and blood pressure of intact, anesthetized dogs and transmembrane action potential characteristics of isolated Purkinje fibers. Verapamil, 100-600 .mu.g/kg, administered in sequential doses i.v. to the intact (donor) animal caused a dose-dependent increase in the P-R interval and a decrease in systemic arterial pressure while exerting no significant effect on the normal, fast response Purkinje fiber action potential. To study effects of verapamil in depolarized fibers, maintained stretch was applied to Purkinje fibers until resting potentials had decreased from .apprx. -91 mV to a stable level of .apprx. -55 mV. For these fibers, verapamil, 400 .mu.g/kg, given as a single injection almost totally suppressed the slow response action potential while prolonging the P-R interval by < 30% above control. These experiments suggest that, in the presence of normal sinus and atrioventricular nodal function, plasma concentrations of verapamil which abolish the slow response action potential should have no major effect on sinus rate and atrioventricular conduction.