Ejection Flow Dynamics Assessed by Ventricular Impulse and Elastance in the Human Hypertensive Heart.

Abstract

Left ventricular elastance is the intrinsic mechanical property of the chambers that generates pressure for a given volume, but the dynamics of the ejection flow are characterized by the ventricular impulse in early systole. The purpose of this study was to characterize the ejection dynamics in the human hypertensive heart according to the concept of ventricular impulse and elastance. Nineteen hypertensive patients without left ventricular hypertrophy (HT-I), 42 hypertensive patients with left ventricular hypertrophy (HT-II), and 43 normotensive subjects (NT) were studied by pulsed Doppler echocardiography. The maximum ejection force (Fmax; kdyne) and the end-systolic wall stress/end-systolic volume index (ESWS/ESVI; kdyne/cm2/ml/m2)were examined as indexes of maximal impulse and elastance, respectively. Fmax was calculated on the basis of the unsteady Bernoulli equation. With regard to impulse and elastance in NT, Fmax was 43.7±6.1 and ESWS/ESVI was 2.26±0.78. In the hypertensive groups, HT-I showed normal Fmax (46.0±5.5) with a significantly higher ESWS/ESVI (3.52±1.12, p<0.01 vs. NT), and HT-II showed a significantly lower Fmax (34.4±7.2, p<0.01 vs. NT) with normal ESWS/ESVI (2.65±1.38). There was a significant inverse correlation between Fmax and left ventricular mass index (r =-0.45, p<0.001). This study shows for the first time the dissociation of maximum impulse and maximum elastance in the human hypertensive heart. The characteristics of elastance are well preserved, but those of the impulse are not preserved in the hypertensive hypertrophied heart. Further more, this dissociation is observed from the undetected hypertrophic state in the human hypertensive heart. (Hypertens Res 1994; 17: 123-131)