[Myocardial diastolic elasticity in chronic adriamycin lesion].

Isolated hearts of the majority of rats receiving 20 mg/kg adriamycin for 10 weeks exhibited normal pump function. Left ventricular diastolic stiffness of these hearts was approximately 1.5 times higher, as compared to control hearts, with the filling pressure in the range of 5 to 20 cm H2O and diastolic pause 23% longer due to bradycardia. Pacing-induced increase in the heart rate up to the control level resulted in further increase in left ventricular diastolic stiffness due to the rise in myocardial stiffness, associated with a fall in cardiac output by 36%. The heart and right atrial compliance determined in separate experiments did not differ significantly from the control. The results suggest that increased left ventricular diastolic stiffness of adriamycin-treated rats seems to be rather due to energy-dependent disturbance in myofibril relaxation than to usually arising myocardial fibrosis.