A study of cardiac vectors in the frontal plane

Abstract

1. 1. The Einthoven triangle has been set forth in the circular form. The circular form correlates easily the polarities written in the six limb leads and the corresponding heart-vector direction in the RLF plane. 2. 2. The average QRS vector was directed toward +45 degrees in normal electrocardiograms, toward +120 degrees in right ventricular hypertrophy, and toward +15 degrees in left ventricular hypertrophy. The average QRS′ vector was directed toward +30 degrees in both complete right bundle branch block and left bundle branch block. The average QRS″ vector was directed toward −165 degrees in complete right bundle branch block, and toward −30 degrees in complete left bundle branch block. 3. 3. In normal electrocardiograms the angle formed by the QRS vector and T vector did not exceed 45 degrees. In right ventricular hypertrophy and left ventricular hypertrophy this angle could range between 0 degree and 180 degrees. In complete right bundle branch block the angle formed by the QRS′ vector and QRS″ vector usually exceeded 90 degrees; the average angle was 150 degrees. In complete left bundle branch block the angle formed by the QRS′ vector and QRS″ vector usually did not exceed 90 degrees; the average angle was 45 degrees. 4. 4. The incidence of complete right bundle branch block was 2 per cent, of which 95 per cent were of the Wilson type. The incidence of complete left bundle branch block was 1 per cent. 5. 5. The T vector could not be determined in 4 per cent of right ventricular hypertrophy and in 11 per cent of left ventricular hypertrophy. 6. 6. In the RLF plane the general direction of activation of a single normal ventricle, either right or left, was nearly the same as that of the normal QRS vector. The route of activation of a blocked ventricle, either right or left, was abnormally altered: toward the right in complete right bundle branch block, and toward the left in complete left bundle branch block. 7. 7. The circular form was found to be advantageous in clinical routine electrocardiographic analysis.