Supernormal contractility in primary hypertension without left ventricular hypertrophy

Abstract

Forty-three subjects with uncomplicated primary hypertension and without echocardiographic left ventricular hypertrophy and 54 normotensive volunteers were studied by two dimensional targeted M-mode echocardiography to evaluate systolic function and contractility before the development of compensatory hypertrophy.The ratio of peak systolic pressure to end-systolic dimension was used to asess left ventricular performance and was divided for either posterior wall thickness or cross-sectional area to generate hypertrophy-independent indices of inotropic state. Fractional shortening was normal in the hypertensive group, despite the increase in end-systolic stress. Systolic pressure/dimension ratio was higher in hypertensive subjects (p < 0.001), as were hypertrophy-independent indices of inotropic state (p < 0.005), which were inversely correlated to left ventricular mass (p < 0.001). Values in 11 hypertensive subjects were above the upper confidence limit of the normal shortening/stress relation, which provides a load-independent measure of inotropic state. They showed high hypertrophy-independent indices of inotropic state (p < 0.01), while the other hypertensive subjects did not. High fractional shortening, wall stress, and systolic pressure (p < 0.01) were found in the subgroup with supernormal performance, while left ventricular mass was not different from that of other subgroups, depicting inadequate left ventricular hypertrophy. The duration of hypertension was the same in the subgroups. Supernormal inotropic state could be considered one form of primary adaptation to high wall stress that serves to maintain systolic ventricular performance.