Myocardial mechanics predict hemodynamic performance during normal function and alcohol-induced dysfunction in rats

Abstract

To determine whether mechanical evaluation of muscle tissue removed from the myocardium can be employed as a direct indicator of cardiac contractile performance in situ, isometric and isotonic parameters of muscle mechanics in vitro were correlated with in vivo global functional characteristics of the same heart. Twelve-month-old animals maintained on standard food and water were employed as representative of normal cardiac function. Animals of identical age with left ventricular (LV) dysfunction induced by oral alcohol (30%) ingestion from 4 to 12 mo were utilized to represent depressed cardiac performance. Accordingly, 24 h after the establishment of the hemodynamic profile for a control or experimental heart, the LV posterior papillary muscle was removed from the same heart and examined isometrically and isotonically. Least squares regression analysis was employed to establish a correlation coefficient and P values between various in vitro and in vivo parameters. Hemodynamic measurements were performed under chloral hydrate anesthesia and LV pump performance was evaluated with respect to aortic and ventricular pressures and the rates of rise and decay of the LV pressure trace. Papillary muscles were evaluated with respect to timing parameters of the isometric and isotonic twitch, the first derivative of isometric tension development, and the speed of muscle shortening at increasing physiologic loads. LV peak rate of pressure rise and decay were then correlated with the various isometric and isotonic properties. Myocardial mechanics and hemodynamics revealed depressed function in the papillary muscles and hearts from alcoholic rats. Moreover, significant correlations were found between the LV rate of pressure change (peak +dP/dt and -dP/dt) and both isometric and isotonic twitch measurements.(ABSTRACT TRUNCATED AT 250 WORDS)