Ionic Changes Associated with Acute Ischemia

Abstract

Harris et al. [1] were the first to appreciate that occlusion of a coronary artery is followed by an increase of potassium in the extracellular space of the area deprived of its circulation. They then performed a series of experiments, which led them to conclude that the increase in extracellular potassium was a major factor, perhaps the major factor in the pathogenesis of the acute ventricular arrhythmias, including ventricular fibrillation, which accompany coronary occlusion [1, 2]. Later, it was shown that acute coronary occlusion leads to a fall in extracellular pH [3] and a rise in extracellular pCO₂ [4] within the ischemic zone. Within the last decade, a variety of new techniques, including ion selective electrodes, nuclear magnetic resonance, and voltage and ion sensitive dyes, have permitted the more precise characterization of the intracellular and extracellular ionic changes that occur when the coronary circulation is abruptly or progressively interrupted and a more accurate correlation of these ionic changes to the associated metabolic, electrical, and mechanical changes. As is usually the case, each new observation has served to bring into sharp focus the limits of our understanding and has spawned a series of new questions. In this presentation, we will briefly review the characteristics, causes, and effects of the potassium and pH changes that occur when coronary flow is interrupted and some of the factors that modify these changes.