Transmural distribution of intrinsic and transmitted left ventricular diastolic intramyocardial pressure in dogs.

The left ventricular transmural distribution of steady diastolic blood flow was measured with microspheres at three constant coronary perfusion pressures and two constant diastolic transmural pressures. The pressure-flow ratio in each layer was near linear allowing calculation of an apparent downstream pressure at zero diastolic transmural pressure (or intrinsic myocardial pressure) of 2.0 to 2.4 kPa (15 to 18 mmHg). When the transmural pressure was 2.67 kPa (20 mmHg), the increment of pressure in the outer 4/5 of the ventricular wall was 0.80 kPa (6 mmHg) (interpreted as transmitted intramyocardial pressure). Thus, intrinsic intramyocardial pressure is large and is a major determinant of diastolic coronary blood flow, and transmitted intramyocardial pressure has its major effect in the subendocardium.