Characteristics of a model of myocardial infarction produced by coronary artery ligation in the rat

The rat model of coronary artery ligation is widely used to study myocardial infarction, ventricular remodeling, and congestive heart failure. Total infarct size and the relationship between endocardial and epicardial infarction were characterized in 691 animals that survived permanent ligation of the left coronary artery. Infarct size was determined from serial histologic sections of the left ventricle (LV), followed by planimetry of muscle and scar circumferences. Mean infarct size was 34.5% ± 13.3% of total left ventricular circumference. Rats surviving longer durations to terminal study had a smaller mean infarct size. Infarct transmurality, as described by the ratio of epicardial-to-endocardial infarct sizes, was 0.78 ± 0.01. The transmurality ratio increased and its variability decreased as infarct size increased. Subendocardial infarcts were more frequent among small infarcts and had smaller areas of endocardial infarction. Although infarct size was highly variable, infarct size indexed to endocardial infarct size was less variable. Infarct size indexed to endocardial infarct size may therefore represent a significantly more powerful method for assessing the effects of treatments to reduce infarct size.