Skeletal Muscle Blood Flow Abnormalities in Rats with a Chronic Myocardial Infarction: Rest and Exercise

The purpose of this study was to determine the regional distribution of blood flow deficit in the skeletal muscle vascular bed of rats with a chronic myocardial infarction (MI) and heart failure (HF). Accordingly, blood flow was determined (via radioactive microspheres) in rats with a small infarction (MI less than 30%) and in rats with a large (MI greater than 30%) infarction, induced by surgically ligating the left main coronary artery, and compared with rats that had received a sham operation. Results demonstrate that blood flow to the hindlimb musculature was significantly (P less than 0.05) less during a given level of treadmill exercise (20% grade and speed of 28 m/min) in the MI groups of rats compared with their sham counterparts. These differences in hindlimb blood flow were the result of blood flow deficits found in the individual muscles of the thigh and leg. Moreover, the blood flow deficits were more pronounced in the MI greater than 30% group of rats compared with the MI less than 30% group. The blood flow deficits found for the MI greater than 30% group of rats were positively correlated with the percentage of fast-twitch oxidative-glycolytic fibers and negatively correlated with the percentage of fast-twitch glycolytic fibers found in the individual muscles. Our study supports the contention that MI rats demonstrate skeletal muscle blood flow abnormalities during exercise. It appears that the degree of blood flow abnormalities produced in rats is dependent on the size of the MI and the amount of left ventricular dysfunction produced in the HF state.