Re-evaluation of the vectorcardiographic criteria for inferior myocardial infarction. Correlation between vectorcardiograms and left ventriculograms.

In 72 patients satisfying the vectorcardiographic criteria described by Young et al, vectorcardiographic findings were compared between a group of patients with an inferior myocardial infarction and a false positive group to increase the specificity of the vectorcardiographic diagnosis of inferior myocardial infarction. The first group was composed of 18 cases, with angiographic findings of inferior myocardial infarction and the false positive group was composed of 54 cases which had no significant narrowing of coronary arteries. Vectorcardiographic parameters such as the angle between the X axis and maximal QRS vector, the duration of initial superior force, the maximal superior deviation (QY) and the maximal inferior deviation (RY) were analyzed and only QY and QY/RY showed statistically significant differences between the 2 groups. Of these two parameters, QY/RY indicated a more definite difference. In addition, the rate of false positive cases was reduced prominently if the criterion of QY/RY above or equal to 0.2 was added to the criteria of Young et al. The direction of the maximal T vector was downward in 2 cases (11%) in the inferior myocardial infarction group, but downward in 44 cases (81%) in the false positive group.