Lack of decreased contractility in hearts from atherosclerotic rabbits

Previous studies have suggested that the contractility of isolated heart muscle removed from rabbits made hypercholesterolemic is decreased. As part of a study evaluating the effects of high-lipid diets on aortic atherosclerosis, we evaluated the contractility of perfused rabbit hearts. Six rabbits were placed on a high-lipid diet for 3 months with cholesterol levels rising to 1700 +/- 400 mg %. After they were killed, their hearts were studied in an isolated, perfused, working heart apparatus at 37 degrees C. Control animals included six rabbits matched for age, six rabbits matched for weight, and six young rabbits. Measurements were made of developed pressure, maximum dP/dt, oxygen extraction, oxygen consumption, and coronary blood flow. There were no significant differences between the contractile parameters of hearts from any group. Since previous studies were conducted with isolated heart muscle at a lower temperature, it may be that hypercholesterolemic effects on membranes may have led to the previous findings of reduced contractility. Our results suggest that hypercholesterolemia, per se, does not decrease cardiac contractility in the rabbit fed a high-lipid diet.