Electrocardiographic effects of experimental myocardial infarction in pigs

Myocardial infarctions were produced in young domestic farm pigs by ligating coronary arteries. Arteries ligated in four groups were (A) left anterior descending, (B) branches of left anterior descending, (C) left circumflex, and (D) right coronary artery. After 7 or 8 days, the hearts were removed and dissected and the infarcted areas measured. Vectorcardiograms were taken before ligation and just before termination. High recording speeds and sensitivities were used so that details of the QRS complexes could be seen. Difference vectors were computed as a function of time during QRS. In groups A and B, statistically significant differences in QRS components before and after ligation were found. Also, there were statistically significant correlations between vectorcardiographic deflections and the ratio of infarct weight to heart weight. The changes were related to known excitation patterns of the pig heart.