Interaction of left ventricular relaxation and filling during early diastole in human subjects

Seventeen patients with coronary artery disease were studied with cineangiography and simultaneous tip manometry at resting heart rate and submaximal tachycardia induced by atrial pacing. During early diastole, defined as the interval from the opening of the mitral valve to the point of minimal left ventricular pressure, 20 percent of total ventricular filling took place at resting heart rate, but 62 percent occurred during tachycardia. Minimal pressure was significantly correlated with the time constant of pressure decay during the isovolumic phase (r = 0.75 at resting heart rate and r = 0.81 during tachycardia). The measured minimal pressure could be predicted by extrapolating the exponential decay of ventricular isovolumic pressure to the time of occurrence of the minimal pressure, which occurred on average 2.7 time constants from the peak negative rate of change of pressure. At resting heart rate the time constant of relaxation was inversely correlated with ventricular inflow volume (r = −0.64) and inflow rate (r = −0.72). It is concluded that left ventricular relaxation has a relevant role in early diastolic pressure-volume relations and increases during tachycardia.