Myocardial ischemia: ionic events in ischemia and anoxia.

The early stages of anoxemia and ischemia are associated with highly selective, reversible defects in sarcolemmal ionic exchange of potassium not necessarily the result of impaired sodium pump function. At a later stage structural defects in the membrane led to irreversible loss of intracellular potassium and creatine kinase. Similar stages can be demonstrated in the sarcolemmal selectivity for divalent cations. The degree of sarcolemmal injury from ischemia can be significantly influenced by the conditions of reperfusion. Reduced calcium content of blood reperfused for only 5 minutes can improve the mechanical recovery of ischemic rabbit ventricle. The influx of calcium during reperfusion impairs those processes required for restoration of sarcolemmal integrity.