Left Ventricular Stiffness Associated with Chronic Pressure and Volume Overloads in Man

Abstract

The relative effects of chronic pressure overload and chronic volume overload on left ventricular diastolic chamber stiffness were examined using a combined hemodynamic and ultrasonic technique in 27 patients. The slope of the left ventricular pressure-diameter relation in late diastole was measured and found to be steep in the groups with pressure or volume overload (9.0 ± 1.8 mm Hg/mm for pressure overload, 5.6 ± 0.9 mm Hg/mm for volume overload) compared with a control group (2.2 ± 0.2 mm Hg/mm). When this slope was normalized for either pressure or diameter, chamber stiffness remained high in the pressure-overloaded ventricles but was only slightly increased in the volume-overloaded ventricles compared with control. Ventricular wall thickness was much greater in pressure-overloaded ventricles (15.6 ± 1.0 mm) than it was in normal (9.0 ± 0.4 mm) ventricles but only slightly increased in volume-overloaded ventricles (10.6 ± 0.9 mm). The large increases in both effective and normalized diastolic stiffness indexes associated with chronic pressure overload suggest an increase in intrinsic left ventricular chamber stiffness, possibly related to an increase in wall thickness. In contrast, chronic volume overload results in only slight increases in normalized diastolic stiffness indexes and wall thickness. It is suggested that differences in the pattern of hypertrophy, which result in a significant disparity in ventricular wall thickness between the two conditions, best account for the observed differences in diastolic left ventricular chamber stiffness.