Arrhythmias and cellular electrophysiological changes during myocardial "ischaemia" and reperfusion

Abstract

Action potentials and ECGs were recorded from isolated guinea pig hearts during low flow (10% of control) and zero flow myocardial “ischaemia” and during subsequent reperfusion. During myocardial “ischaemia” ventricular tachycardia and ventricular fibrillation were significantly more frequent during low flow, than zero flow “ischaemia” (Pmax, and duration, and increased conduction time. During low flow “ischaemia”, electrophysiological change reached a nadir at 12±3 (mean±SEM) min, and in all cases spontaneous electrophysiological recovery in action potentials and conduction time preceded ventricular arrhythmias, which occurred at 18±3 min. In contrast during zero flow “ischaemia” electrophysiological changes were more marked and no recovery was observed. Refractory periods were initially prolonged by both forms of “ischaemia”, followed by a marked shortening. The initial prolongation was more marked and subsequent shortening less during zero than low flow “ischaemia”. Reperfusion induced electrophysiological recovery in all hearts; however reperfusion VF was preceded by further shortening of action potential duration and refractory period. These results indicate that residual flow during myocardial “ischaemia” is associated with spontaneous electrophysiological recovery and more frequent ventricular arrhythmias. The severity of “ischaemia” is less important than its duration for the development of reperfusion arrhythmias.