T: Systolic and diastolic pressure gradients within the left ventricular wall.Am J Physiol 1980;238(Heart Circ Physiol 7):H625-H630

within the left uentriczdar waZZ. Am. J. Physiol. 238 (Heart Circ. Physiol. 7): H625-H630, 1980.-Left ventricular systolic and diastolic intramyocardial pressures were measured in 26 open-chest dogs using micromanometers positioned in the sub-endocardium and subepicardium. Systolic pressure in the sub-endocardium, 190 t 5 mmHg (mean t SE), exceeded left ventricular intracavitary systolic pressure, 134 t 4 mmHg (P < 0.001). Systolic pressure in the subepicardium, 100 k 3 mmHg, was lower than left ventricular intracavitary systolic pressure (P < 0.001). The maximal rate of rise of subendocardial pressure was comparable to the maximal rate of rise of left ventricular intracavitary pressure (2,470 t 150 mmHg vs. 2,410 t 150 mmHg) (NS). The maximal rate of rise of subepicardial pressure, 1,030 t 80 mmHg, was lower than the maximal rate of rise of intracavitary pressure (P c 0.001). During diastole, subepicardial pressure, 28 2 2 mmHg exceeded left ventricular end-diastolic pressure, 8 t 1 mmHg (P < O.OOl), and it also exceeded diastolic subendocardial pressure, 13 t 1 mmHg (P < 0.001). These observations indicate that a transmural pres-sure gradient exists during diastole, and the direction of the gradient is opposite to that which occurs during systole. Be-cause coronary extravascular resistance is directly related to intramyocardial pressure, the transmural distribution of coro-nary flow is partially explained by these observations. Trans-mural differences of ventricular contractile performance also are suggested to be present. coronary circulation; myocardial contraction; ante; energy metabolism; regional blood flow vascular resist-TO CHARACTERIZE the mechanical properties of cardiac muscle in the various phases of the cardiac cycle, many investigators have attempted to measure intramyocardia