Biochemical changes of ischemia.

Normothermic ischemic arrest by aortic cross-clamping, a widely used clinical technique, is associated with metabolic changes in the myocardium that are incompletely understood. The effects of aortic cross-clamping on glycolytic pathways as well as associated morphological changes are discussed. Emphasis is placed on the conservation of high-energy phosphate moieties during the period of cross-clamping as well as during reperfusion. A marked reduction in total high-energy phosphates (62%) and glycogen (63%) and an increase in lactate production (243%) denote a shift to anaerobic metabolism during the period of arrest. Despite reperfusion, total high-energy nucleotides remained depressed. The data suggest that persistent abnormal myocardial carbohydrate metabolism and low levels of high-energy nucleotides prevent recovery of contractility following normothermic ischemic arrest and reperfusion.