THE Q WAVE IN L III AND AVF OF THE ELECTROCARDIOGRAM. A VECTORCARDIOGRAPHIC ANALYSIS WITH THE USE OF THE FRANK SYSTEM.

Seventy-three consecutive patients with a Q wave in Lead III and aVF in the electrocardiogram were studied. Vectorcardiograms were recorded with the use of the Frank system. In 32 cases the ECG's were compatible with the diagnosis of an inferior myocardial infarction based on a Q wave in Lead III and/or aVF greater than 0.04 second duration and greater than 25 per cent of the amplitude of the R wave. In this group, there were 16 patients with coronary disease and the VCG confirmed the electrocardiographic diagnosis of an infarction in 14 cases. In 13 of the other 16 cases without history of coronary disease the VCG did not suggest the presence of an infarction. In all 17 cases with questionable electrocardiographic diagnosis of an inferior infarction, and without history of coronary disease, the VCG denied the presence of an infarction. In 18 cases with small Q III or Q aVF the VCG's were within normal limits. In two cases with normal Q III and Q aVF the VCG's did not detect the presence of an infarction in both cases. The vectorcardiographic diagnosis of an inferior myocardial infarction was based on the superior orientation (at or above 360 degrees) of the 10, 20, 25 and 30-msec vectors in the frontal plane, superior displacement of the maximum QRS vector and clockwise rotation. In the left sagittal plane the 10, 20, 25 and 30-msec vectors were oriented at or above 180 degrees with the loop rotating counterclockwise. The data presented suggest that vectorcardiography is a useful adjunct to electrocardiography in the diagnosis of an inferior myocardial infarction.