Comparison of the Effects of Regional Ischemia and Hyperkalemia on the Membrane Action Potentials of the In Situ Pig Heart

Publisher Website
Google Scholar
Abstract
APD During Ischemia. Introduction: This study was designed to determine the role of increased extracellular potassium [K+]e on action potential duration (APD) in the in situ porcine heart during acute regional no‐flow ischemia. Methods and Results: In open chest, anesthetized swine, an arterial shunt from the carotid artery to the mid‐left anterior descending coronary artery was created through which a solution of KCl was infused to raise [K+]e, Myocardial [K+]e, was determined by potassium‐sensitive electrodes, and transmembrane action potential was recorded by floating glass microelectrode. During the first 2 minutes of ischemia, APD at 90% repolarization (APD90) lengthened by 31.2 ± 1.1 msec (P < 0.05). The comparable increase in [K+]e alone shortened APD90, During the next 6 minutes of ischemia. [K+]e, rose to 11.3 ± 0.3 mM and APD90, showed a decrease. However, the comparable increase in |K+]e, by infusion of KCl caused further shortening of APD90, at similar levels of [K+]e. Conclusions: Acutely ischemic myocardium showed a brief increase in APD90, during the first 2 minutes of ischemia, followed by a fall in APD90, after 2 minutes of ischemia, but the shortening is less than anticipated by the rise in [K+]e. Thus, we hypothesize that other component(s) of ischemia may inhibit action potential repolarization.

This publication has 22 references indexed in Scilit: