LEFT-VENTRICULAR END-SYSTOLIC PRESSURE-DIMENSION AND STRESS-LENGTH RELATIONS IN NORMAL HUMAN-SUBJECTS

To determine whether the left ventricular end systolic pressure-dimension and end-systolic stress-dimension relations in human beings are linear and sensitive to altered contractility, we studied 13 normal subjects during methoxamine infusion and with postextrasystolic potentiation induced by an external mechanical cardiac stimulator. End-systolic diameter was obtained with echocardiography and end-systolic pressure was estimated in six subjects from the dicrotic notch of a simultaneously recorded carotid pulse tracing, standardized by cuff pressure, whereas in seven subjects intraarterial pressure was recorded. For each subject, the end-systolic pressure-dimension relation was linear (r = 0.83-0.99) over a range of 76 mm Hg (84 to 160) for end-systolic pressure. The mean slope of the end-systolic pressure-dimension line was 62 ± 22 mm Hg/cm. Peak systolic pressure was also linearly related to end-systolic diameter (r = 0.82-0.99) over a range of 100 mm Hg (104 to 204). End-systolic stress was a linear function of end-systolic dimension as well (r = 0.93-0.99) over an end-systolic stress range of 181 g/cm2. With postextrasystolic potentiation the potentiated beat had a smaller end-systolic dimension for any given end-systolic pressure and thus shifted the end-systolic pressure-dimension relation to the left. Thus, end-systolic pressure-dimension and stress-dimension relations in human subjects appear to be linear and are sensitive to the inotropic state. © 1979.