Waveform patterns in Frank lead rest and exercise electrocardiograms of healthy elderly men

Waveform patterns of P, ST and T vector functions of Frank lead rest and exercise vectorcardiograms (VCG) of 375 ostensibly normal males, aged 50 to 70 yr, were evaluated by waveform vector analysis (WVA). This procedure suitably quantified waveform information, providing a stable reduced data base comprising mean vector (MV), gradient vector (GV), convex vector (CV), sigmoid vector (SV), and quaternary vector (QV). In resting VCG, most of the waveform vectors were clustered fairly uniformly in space with tight directional distributions of widely varied magnitudes; normal limits of these magnitudes were established and their spatial frequency distributions mapped. Individual vectors' contributions to the overall waveform pattern of the vector function were quantified with waveform power indices. The GV accounted for >90% of ST waveform power, whereas the CV and GV jointly accounted for about 90% of T waveform and > 80% of P wave waveform variation. Exercise elicited significant changes in magnitude and orientation of some vectors. All P wave vectors increased; by an average of 68% in P MV, 80% in P GV, 64% in P CV, and by 41% in P SV. The P waveform changes were compatible with enhancement of surface potentials associated with excitation of the right atrium. By contrast, T CV and T QV decreased slightly. ST MV shifted clockwise to the right and upward whereas ST GV rotate in the opposite direction toward inferior and left. ST segment gradients and the corresponding ST GV were independent of heart rate, whereas the (conventional) ST slope tended to increase unpredictably with increasing heart rate.