Effect of Alterations of Coronary Blood Flow on the Oxygen Consumption of the Working Heart.

• The finding that the oxygen consumption of the empty, nonworking heart could be influenced by the rate of coronary blood flow was at variance with the concept that myocardial oxygen consumption is determined primarily by the mechanical activity of the heart." Furthermore, the results of these studies in the nonworking heart were not in accord with the preliminary results of experiments in the isolated supported heart made available to us by Dr. S. J. Sarnoff. The latter experiments suggested that, in the heart performing external work at a constant level, the myocardial oxygen consumption was not altered by variations in coronary blood flow. These considerations made it interesting to study the effects of altering coronary blood flow on the oxygen consumption of the working heart, utilizing a preparation similar to that which had been employed to study the heart which performed no external work.