Sexual Dimorphism in the Electrocardiographic Dynamics of Human Ventricular Repolarization

Abstract

Background-Previous characterizations of sex differences in ST-T waveform voltages have largely focused on amplitudes at selected time points during repolarization, subject to potential distortions from variations in heart rate (HR) or reliance on a JT-normalized time scale. Methods and Results-Using digitized 12-lead ECGs from 553 normal adults (426 males) with HRs confined to 60Ϯ1, 70Ϯ1, or 80Ϯ1 bpm, we derived X, Y, and Z lead voltages and then generated, for each HR category by sex, summary (population mean) resultant spatial vector amplitudes (ST-T XYZ ) and instantaneous slopes (dV/dt XYZ ) at successive 4-ms intervals following the J point. Within each HR category, there was an early intersex divergence of ST-T XYZ trajectories (95% CIs nonoverlapping), with men exhibiting 2-to 3-fold greater dV/dt XYZ values during the ST segment and achieving greater maximum T XYZ and dV/dt XYZ values than women; descending T XYZ limbs were relatively more concordant between sexes but still steeper in men. The early sex differences in repolarization dynamics persisted in multiple regression analyses that took into account age and a morphometric index of left ventricular mass. In men, absolute values of extrema of T XYZ and dV/dt XYZ varied inversely with HR. Conclusions-At physiological resting HRs, the spatial ST-T vector voltage time trajectory is steeper in men than in women, beginning virtually from the J point. In addition to its mechanistic implications, the demonstration of marked sensitivity of ST-T XYZ and especially dV/dt XYZ to sex raises the possibility that these time-based, ECG-derived parameters might be informative in pathophysiological studies of ventricular repolarization.

Principal Component Analysis of the T Wave and Prediction of Cardiovascular Mortality in American Indians

“…16,34 In contrast to the gender differences in the PCA ratio, men and women had similar QTd values despite longer durations of repolarization and lower T-wave areas in women. 1,33 This reproduces findings in healthy subjects 25 and suggests a possible explanation for the gender differences in performance of QTd in the present study. It is intriguing to speculate that this might reflect the method used to determine T-wave offset in the present study, which is dependent on identification of the maximal slope of the descending limb of the T wave, 20,21 in light of recent observations that the absolute slope of each limb of the T-wave is steeper in men than in women.…”

“…25 Gender differences in the PCA ratio can be attributed to the lower T-wave amplitudes and T-wave areas found in women despite similar or slightly longer durations of repolarization, 1,33 which would on average result in higher ratios of the second to first eigenvalues in women than in men. Indeed, gender differences in the PCA ratio in healthy subjects disappeared after adjusting for differences in T-wave area and body mass index between men and women.…”

“…It is intriguing to speculate that this might reflect the method used to determine T-wave offset in the present study, which is dependent on identification of the maximal slope of the descending limb of the T wave, 20,21 in light of recent observations that the absolute slope of each limb of the T-wave is steeper in men than in women. 33 The greater descending slope in men could possibly counteract the greater T-wave amplitude in men than in women, 1,33 producing similar QT interval durations in men and women using this computerized approach, despite clear gender differences in other measures of repolarization heterogeneity. 1,25,33 …”

“…33 The greater descending slope in men could possibly counteract the greater T-wave amplitude in men than in women, 1,33 producing similar QT interval durations in men and women using this computerized approach, despite clear gender differences in other measures of repolarization heterogeneity. 1,25,33 …”

Gender differences in stability of the instantaneous patterns of body surface potentials during ventricular repolarisation

“…This was confirmed by BIDOGGIA, et al (2000), who also reported that the maximum amplitude of the T-wave and the slope of the ST are higher in males, whereas the J-T peak interval is shorter. LEHMANN and YANG (2001) found differences in the level and speed of variation of potentials over the whole of repolarisation. Gender-related differences in body surface maps have been reported in GREEN et al (1985).…”