The electrocardiogram of rats with an old extensive myocardial infarction

The electrocardiographic alterations of old murine myocardial infarction have not been well characterized. In the present study, adult Wistar rats of both sexes were infarcted by left coronary artery ligation and the electrocardiogram was recorded 1 to 11 months later. When compared to sham-operated rats, animals with large infarcts, identified on the basis of extensive transmural scars, showed (P less than 0.01) a marked rightward deviation of the QRS axis (+125.3 degrees +/- 34.3 degrees vs +59.9 degrees +/- 15.9 degrees), a high incidence of Q waves (88% vs 0% in classic lead 1), a decrease in QRS amplitude index (0.66 +/- 0.31 mV vs 1.00 +/- 0.23 mV), a discrete increase in PR interval (58 +/- 7 ms vs 53 +/- 5 ms) and greater P wave amplitude. The present results show that the electrocardiogram (EKG) is a reliable tool for diagnosis of old extensive infarctions in rats.