The initial 0.04 second polar vector of the QRS loop as an aid in the detection of a myocardial infarction.

Thirty-one normal subjects and 16 subjects with documented myocardial infarction were studied. The Frank system of vectorcardiography was used. The polar vector and 0.04 polar vector were calculated in all. The 0.04 polar vector was abnormally directed in all cases of documented infarction, including 2 subjects with a documented infarction but a "suggestive" electrocardiogram. The results of this preliminary study suggest that this method of vectorcardiographic analysis may be of a clinical value in those cases with a previous myocardial infarction in which the present electrocardiogram is suggestive but not diagnostic of an infarction. The results also demonstrate the greater diagnostic value of the 0.04 polar vector over the polar vector in detecting myocardial infarction.