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

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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 < 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), 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.