Inotropic and lusitropic effects of incremental doses of dobutamine in dogs with right ventricular apical pacing-induced cardiac dysfunction.

Abstract

This study aimed to assess the effects of incremental doses of dobutamine on diastolic function in healthy and rapid ventricular apical pacing (RVAP)-induced cardiac dysfunction anesthetized dogs. Inotropic and lusitropic effects of dobutamine (2, 4, 8, and 12μgkg-1 min-1 ) were assessed through left ventricle (LV) pressure-volume relation and Doppler echocardiography in six female dogs before and after 8weeks of RVAP. Peak rate of LV pressure fall (-dP/dtmin ) improved with doses >4μgkg-1 min-1 in healthy (4,490±970 vs. 3,265±471mmHg/s, p<0.05) and >8μgkg-1 min-1 in RVAP dogs (3,385±1,122 vs. 1,864±849mmHg/s, p<0.05) while the time constant of relaxation (tau) reduced with doses >4μgkg-1 min-1 in both groups (healthy: 24.0±3.7 vs. 28.2±4.9ms; RVAP: 32.6±8.5 vs. 37.5±11.4ms, p<0.05) comparing with baseline. Indices of relaxation (-dP/dtmin and tau) suggested preserved lusitropic response in contrast with markedly reduced indices of contractility in the RVAP group compared with healthy group at same infusion rates. Doppler echocardiography showed significant reduction of elastic recoil in failing hearts. The results of this study demonstrated maximal positive lusitropic effects of dobutamine at a dose of 8μgkg-1 min-1 in ventricular pacing-induced cardiac dysfunction without further impairment of ventricular filling.