Systolic and diastolic pressure gradients within the left ventricular wall

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Abstract
Left ventricular systolic and diastolic intramyocardial pressures were measured in 26 open-chest dogs using micromanometers positioned in the subendocardium and subepicardium. Systolic pressure in the subendocardium, 190 .+-. 5 mm Hg (mean .+-. SE), exceeded left ventricular intracavitary systolic pressure, 134 .+-. 4 mm Hg (P < 0.001). Systolic pressure in the subepicardium, 100 .+-. 3 mm Hg, 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 (2470 .+-. 150 mm Hg vs. 2410 .+-. 150 mm Hg) (NS [not significant]). The maximal rate of rise of subepicardial pressure, 1030 .+-. 80 mm Hg, was lower than the maximal rate of rise of intracavitary pressure (P < 0.001). During diastole, subepicardial pressure, 28 .+-. 2 mm Hg exceeded left ventricular end-diastolic pressure, 8 .+-. 1 mm Hg (P < 0.001), and it also exceeded diastolic subendocardial pressure, 13 .+-. 1 mm Hg (P < 0.001). A transmural pressure gradient evidently exists during diastole, and the direction of the gradient is opposite to that which occurs during systole. Because coronary extravascular resistance is directly related to intramyocardial pressure, the transmural distribution of coronary flow is partially explained by these observations. Transmural differences of ventricular contractile performance also may be present.

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