ANALYSIS OF RIGHT AND LEFT-VENTRICULAR PERFORMANCE OF THE RAT-HEART WITH CHRONIC MYOCARDIAL-INFARCTION

1. The rat heart develops a compensatory hypertrophy after infarction which is secondary to volume overload in the left ventricle (LV) and t o pressure overload in the right ventricle (RV). This study was undert aken to determine whether the reduced inotropic response to Ca2+ prese nted by the LV of infarcted rats extends to the RV and whether this he modynamic profile in vivo affects the contractile performance of the v entricles assessed in vitro. 2. Male adult rats were submitted to left coronary artery ligation to produce infarction (Inf) or to a sham sur gery (SO) and used 4 to 5 weeks later. The hemodynamic data were recor ded in the anesthetized animals and the systolic performance of both v entricles was evaluated in vitro in the hearts perfused by the Langend orff technique. The isovolumic systolic pressure (ISP) developed by bo th ventricles was measured at various diastolic pressures (0 to 30 mmH g) and Ca2+ concentrations (0.62, 1.25, and 2.50 mM). 3. The RV systol ic pressure was higher in Inf (N = 12) than in SO (N = 12) rats (42 +/ - 5 vs 26 +/- 1 mmHg, P<0.05). A positive and linear correlation (r = 0.86, P<0.01) between RV systolic pressure and the RV weight to body w eight ratio in Inf rats was observed. 4. Length-dependent activation, evaluated by using normalized ventricular function curves, was unchang ed in the RV of Inf hearts. In the mf LV, however, a slight improvemen t of the normalized systolic performance was observed in relation to S O hearts for diastolic pressures higher than 15 mmHg. 5. A similar dep ression of the inotropic response to Ca2+ was observed in both ventric les of Inf hearts. Moreover, for Inf hearts the increase of the ISP to Ca2+ flattened at lower Ca2+ concentrations in relation to the SO gro up.