ABSTRACT
The electrocardiogram (ECG) has been a useful tool to identify ischemia in humans and laboratory animals. Previous ECG studies showed that presence of pathological Q waves in lead DI in rats submitted to ligature of the left coronary artery (LCA) is a good predictor of successful myocardial infarction (MI). This study aimed to determine the sensitivity and the specificity of these ECG findings to predict successful MI. Male Wistar rats were submitted to surgical ligature of the LCA (N=86) or sham-operation (SO, N=16). ECG was recorded under halothane/ether anesthesia before surgery and 1, 3, 5, 7, and 15 days later. MI was determined by the presence of a transmural fibrous scar. Sixty-nine rats survived and 60 showed fibrous scar indicating a successful production of MI (18 and 42 animals were analyzed 1 or 15 days after MI, respectively). Twenty-four hours after, Q amplitude was linearly related to infarct size (r=-0.778; P<0.01), but not 15 days after (r=-0.416; P>0.05). In 53 out of 60 rats with transmural scar, Q wave in lead DI was identified in the ECG. Absence of Q wave occurred in 7 animals. The sensitivity was 88% (CI(95)=83-93%). Nine animals submitted to coronary ligature did not show infarct scar. One of these animals, however, showed Q wave in DI, indicating a specificity of 77% (CI(95)=65-104%). In conclusion, ECG can be used as a reliable tool to identify MI and can be used to predict the infarct size as earlier as 1 day after LCA ligation in rats.
