An Of tidal Journal of the American Heart Association BRIEF REVIEWS Electrophysiological Changes and Ventricular Arrhythmias in the Early Phase of Regional Myocardial Ischemia

IN RECENT years, a number of review articles devoted entirely or partly to electrical changes and arrhythmias during ischemia and infarction have appeared (Wit and Bigger, 1975; Coraboeuf et al., 1976; Arnsdorf, 1977; Elharrar and Zipes, 1977; Bigger et al., 1977; Wit and Cranefield, 1978; Lazzara et al., 1978; Carmeliet, 1978; Cranefield and Wit, 1979). Most of what is known about cellular electrophysiological changes is derived from experiments on isolated tissue, either excised at different times after coronary artery occlusion, or taken from normal hearts and superfused with solutions altered in such a way as to imitate conditions occurring in ischemic hearts. (Friedman et al., 1973; Lazzara et al., 1974; Cranefield, 1975). The acquisition of electrophysiological data from intact hearts with the same degree of accuracy as in isolated tissue is limited by the techniques available at present. Therefore the description of the mechanisms for arrhythmias and conduction disturbances observed in intact hearts is based mainly on indirect evidence. Most experimental work on ischemia has been conducted in late stages (hours or days) after occlusion. The changes occurring in the very first minutes after coronary occlusion follow a very rapid time course, and a stable electrical situation is not present. Thus anlaysis of the electrophysiological changes in the very early phase of ischemia is hampered by both the technical difficulties of obtaining reliable recordings from intact hearts and by the rapidly changing electrical conditions.