Effect of afterload on the left ventricular pressure fall during isovolumic relaxation period in man.

Abstract

To assess the effect of afterload on the left ventricular pressure (LVP) fall during isovolumic relaxation period (IRP) in man, we examined the peak (-)dP/dt, (-)dP/dt upstroke pattern in IRP, and time constant (T) in 15 patients [normal (N): 5 valvular heart disease (VHD): 5, dilated cardiomyopathy (DCM): 5]. LVP and echocardiographic internal diameter were measured simultaneously at rest and after about 30 mmHg increment of LV peak systolic pressure (PSP) by drip infusion of angiotensin (20 ng/kg/min). After augmentation in afterload, heart rate (HR) increased slightly in VHD. T increased significantly (p less than 0.05) in N (from 32 +/- 3 to 39 +/- 4 ms) and DCM (from 56 +/- 18 to 72 +/- 12 ms), but not in VHD (from 41 +/- 5 to 46 +/- 8 ms) probably due to increased HR. LV end-systolic dimension had the same trend as T. Although there was no significant change in peak (-)dP/dt in N (from 1937 +/- 385 to 1945 +/- 189 mmHg/s), VHD (from 1521 +/- 210 to 1730 +/- 462 mmHg/s), or DCM (from 814 +/- 143 to 814 +/- 131 mmHg/s), the (-)dP/dt upstroke pattern during IRP became nonexponential in N and more downward convex in VHD or DCM. Thus, these changes of T and (-)dP/dt upstroke pattern suggest the afterload dependence of LVP fall during IRP in normal and diseased hearts.