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(Circulation. 1995;91:1213-1220.)
© 1995 American Heart Association, Inc.

Articles

Disparate Effects of Early Pressure Overload Hypertrophy on Velocity-Dependent and Force-Dependent Indices of Ventricular Performance in the Conscious Baboon

Brian D. Hoit, MD; Yanfu Shao, MD; Marjorie Gabel; Richard A. Walsh, MD

From the Division of Cardiology, University of Cincinnati Medical Center, Cincinnati, Ohio.

Correspondence to Brian D. Hoit, MD, Associate Professor of Medicine, Division of Cardiology, University of Cincinnati Medical Center, 231 Bethesda Ave, ML 542, Cincinnati, OH 45267-0542.

Background The effects of early pressure overload on left ventricular (LV) chamber mechanics in the primate heart are poorly understood.

Methods and Results To test the hypothesis that early LV pressure overload hypertrophy is associated with depression of velocity-dependent indices of LV systolic (LV dP/dt) and diastolic function (time constant of relaxation, tau) but unchanged systolic elastance (E_es), we studied six conscious baboons instrumented with LV micromanometers and LV dimension and wall thickness sonomicrometers. Loading conditions were altered by pharmacological angiotensin II generation both before and 12 weeks after producing renovascular hypertension (2 kidney, 1 clip). The LV systolic pressure (149±11 [SD] versus 114±5 mm Hg) and LV mass (125±25 versus 91±20 g) were greater 12 weeks after than before (both P<.05). Both E_es and E_es normalized for LV mass were similar before versus 12 weeks after (23.0±9.6 versus 22.3±9.8 mm Hg/mL and 26.5±14.5 versus 19.8±12.5 mm Hg/mL, respectively; both P=NS). At matched LV systolic and diastolic pressures, LV fractional shortening was similar (18.6±6.8% versus 21.6±4.9%), but the time constant of LV isovolumic relaxation was significantly longer (42.3±5.3 versus 31.4±7.0 ms, P<.05) and LV dP/dt and V_cf were significantly less (1891±352 versus 2342±284 mm Hg/s and 0.9±0.4 versus 1.1±0.3 circ/s, respectively; both P<.05) 12 weeks after than before.

Conclusions In conscious baboons with systemic arterial hypertension and early LV hypertrophy, there is depression of velocity-dependent indices of LV contraction and relaxation but unaltered force-dependent measures of contractility.

Key Words: ventricles • hypertrophy • elasticity • hypertension • systole

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