Myocardial damage by ventricular fibrillation in isolated perfused rat hearts, and its underlying mechanisms

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Abstract
In isolated perfused rat hearts ventricular fibrillation (VF), elicited electrically and persisting further spontaneously, led to an extensive release of creatine kinase (CK). Coronary flow volume and oxygen consumption were increased. In contrast, the CK release was only very small in hearts which were stimulated permanently with rhythmic impulses of 10 Hz, whereas the increase in coronary flow and oxygen consumption was significantly greater. When a relative ischemia was induced by perfusion at a low pressure, the CK release from fibrillating hearts was not greater, but less than at a higher perfusion pressure. It appeared unlikely, therefore, that the CK release from fibrillating hearts was simply due to an oxygen deficiency, although a decrease of ATP and glycogen, and an increase of glucose-6-phosphate and lactate in the myocardium were found. When VF was interrupted by lidocaine, the enzyme leakage was reduced only in the experiments with the higher perfusion pressure. A partial restoration of the myocardial metabolites after 1 h was observed. Findings in maximally ischemic hearts further supported the idea that the enzyme release in fibrillating hearts was not merely due to a lack of oxygen. Complete interruption of the coronary perfusion led to the release of only small CK activities during subsequent coronary reperfusion, whereas the metabolic alterations were more distinct than in fibrillating hearts. Mechanisms responsible for the enzyme release during fibrillation, besides a moderate oxygen deficiency, are discussed.