Sex differences in the vectorcardiogram.

In a study of 101 normal men and 102 normal women (mean age, 42.5 and 42.6 years, respectively), significant sex differences were observed in 43 of 64 vectorial items analyzed (initial 0.02-sec and 0.025-sec vectors, maximal QRS and T vectors, terminal 0.02-sec vectors in frontal, horizontal left sagittal planes; Q, R, S, and T deflections in Frank's X, Y, and Z leads). The initial QRS vectors are oriented more inferiorly and posteriorly in women than in men, the maximal QRS vectors more inferiorly, the terminal vectors more leftward and superiorly, the T vector more posteriorly and inferiorly. The QRS-T angle is smaller. There is a significant tendency to smaller magnitude of all planar vectors and Q, R, S, and T deflections (except Sy) in orthogonal leads in women, and a greater incidence of initial counterclockwise rotation in the frontal plane QRS loop. Thus, sex differences show up better in the VCG than in the ECG. Separate normal 95 percentile limits for men and women are presented for all items with significant sex differences and pooled limits for VCG items without significant differences.