T loop in posterior myocardial infarction: a useful clue to vectorcardiographic diagnosis

In order to differentiate posterior (posterolateral) myocardial infarction (PMI) from the anterior shift of the QRS loop in "normal variant" cases using a vectorcardiogram, the T loop as well as the QRS loop in the transverse plane (TP) were analyzed in 34 elderly Japanese males with angiographically-proven PMI and in 197 elderly Japanese males with normal coronary arteries and ventricles. T loops in the TP were longer, narrower and more anterior in PMI cases. After this analysis, we propose new criteria for PMI: (A and B) A: maximal T vector equal or anterior to 60 degrees in TP B: at least two of the following three: maximal QRS voltage/maximal T voltage in TP equal to or less than 3.0; QRS-T angle equal to or less than 75 degrees in TP; width/length of T equal to or less than 0.15 in TP. These new criteria for PMI are more specific (p less than 0.01) and more sensitive (p less than 0.05) than Hoffman's criteria.