DOX-Induced Myopathy and Diastolic Stiffness of the Left Ventricular Myocardium of Rat Heart under Conditions of Dobutamine Load.

We studied cardiac relaxation disorders on a rat model of DOX-induced cardiomyopathy (DOX, 2 mg/kg/week for 2 weeks). Left ventricular pressure and volume were synchronously recorded in vivo at baseline and under increased doses of dobutamine (DBA, 1-32 μg/kg/min). Left ventricular diastolic stiffness constants were calculated; the dose dependence of HR and isovolumic relaxation time (tau) was evaluated. In rats with cardiomyopathy, the diastolic stiffness constants increased with increasing the DBA doses, which was absent in the control; HR and tau showed opposite changes. The mean angular coefficient of linear trends in the dose dependence of stiffness constants on infusion was 2.98 × 10-4 in rats with cardiomyopathy and -0.014 × 10-4 in control animals. Thus, DOX cardiomyopathy led to an increase in the diastolic stiffness constants against the background of DBA treatment.