The role of coronary perfusion pressure in the control of mechanical performance and oxygen consumption in the isolated rat heart.

The dependence of myocardial mechanical activity and O2-consumption (MVO2) on coronary perfusion pressure (PP) was studied in isolated rat hearts perfused by the modified Langendorff technique. Stepwise elevation of PP (20-160 mmHg) resulted in a linear increase of coronary flow and left ventricular systolic pressure, in a biphasic rise of MVO2 and a sigmoid change of dp/dtmax, dp/dtmin and effluent pO2. Drainage of the left ventricle eliminated the slowly rising phase of MVO2 in the high (80-160 mmHg) PP range. Thebesius flow was a linear function of PP. The data suggest that PP controls contractility and MVO2 by enhancing O2 supply in the low (20-60 mmHg) PP range, whereas at higher pressures (80-160 mmHg) the increased left ventricular filling (Thebesius flow) is responsible for the positive relationship in the isolated rat heart.