Studies of Myocardial Aetomyosin and Myosin After Shock , Acute Hemorrhage , Acute Hypoxia , and Cardiopulmonary Bypass

A DECREASE in cardiac efficiency is observed in dogs submitted to endotoxic shock, acute hemorrhage, and after heart-lung bypass. This may result from diminished coronary blood flow, tissue hypoxia, or lower oxygen tension of arterial blood in the cases of endotoxic shock and acute hemorrhage. The otiology of a shocklike syndrome following cardiopulmonary bypass has been studied by Brom and Nautal and has been attributed to metabolic alterations; however, the precise mechanism of decrease in the myocardial function is unknown. Since the myocardial mechanical efficiency greatly depends upon the various chemical activities which lead to muscular contraction,2 such as the energy conversion processes, physicochemical properties of the contractile proteins, or the coupling processes of the wave of excitation at the cell membrane with mechanical contraction of the myocardium,3 it seemed possible that interference with these processes at any point might lead to inefficiency of myocardial contraction. Specifically, since the energy utilization process within the myocardium is directly related to the physicochemical properties of cardiac contractile protein, and since the actomyosin-ATP (adenosinetriphosphate) system, together with