Influence of Coronary Flow upon Oxygen Consumption and Cardiac Performance

The influence of induced changes in coronary flow upon oxygen consumption and cardiac performance were observed in the in situ isovolumic left ventricle. This preparation was established with auxiliary pumps which bypass the dog's right and left heart and by inserting a balloon into the left ventricle so that the latter ejected no blood. Coronary flow was set or varied by a retrograde aortic perfusion pump. Oxygen consumption of the heart was found to be coronary flow dependent or independent, according to the conditions of the experiment. When it is coronary flow dependent there is usually a similar relationship between coronary flow and cardiac performance. In a single preparation, it was sometimes found that cardiac oxygen consumption was coronary flow dependent at lower rates of coronary flow and independent at higher flow rates. Possible explanations and clinical applications are given.