Left ventricular contractility is impaired following myocardial infarctionin the pig and rat: Assessment by the end systolic pressure-volume relation using a single-beat estimation technique and cine magnetic resonance imaging

The end systolic pressure-volume relation (ESPVR) has been shown to be a re latively load independent measure of left ventricular (LV) contractility. R ecently, several single-beat ESPVR computation methods have been developed, enabling the quantification of LV contractility without the need ro alter vascular loading conditions on the heart. Using a single-bear ESPVR method, which has been validated previously in humans and assumes that normalized elastance is constant between individuals of a species, we studied the effe cts of myocardial infarction on LV contractility in two species, the rat an d the pig. In our studies, LV pressure was acquired invasively and LV volum e determined noninvasively with magnetic resonance imaging, at one week pos tinfarction in pigs and at 12 weeks postinfarction in rats. Normalized syst olic elastance curves in both animal species were not statistically differe nt from that of humans. Also, the slope of the ESPVR (E-es) decreased signi ficantly following infarction in both species, while the volume-axis interc ept (V-0) was unaffected. These results indicate that a single-beat ESPVR m ethod can be used to measure the inotropic response of the heart to myocard ial infarction, and that the basis for this method (i.e., constant normaliz ed elastance) is applicable to a variety of mammalian species. (C) 2000 Bio medical Engineering Society. [S0090-6964(00)00205-8].