Twelve‐Lead QT Dispersion Is Smaller In Women Than In Men

Abstract

Background: Although gender differences in the corrected QT interval (QT,) have been described, gender differences in QT dispersion (QTd) have not been carefully evaluated. This study was designed to measure QTd in 22 young healthy women and in 20 healthy men.Methods and Results: Twelve-lead ECGs were recorded at rest and following double autonomic blockade with atropine 0.04 mg/kg and propranolol 0.2 mg/kg during the menstrual, follicular, and luteal phases of the menstrual cycle, which was confirmed by hormone levels. Men were studied during three separate visits as controls. In women, there was no difference in QTd among the three phases of the menstrual cycle, and thus all three visits were pooled for comparison with men. The 12-lead QT dispersion (maximumminimum QT) was larger in men than in women at baseline (41 t 17 ms vs 35 5 16 ms), and this difference tended to decrease after double autonomic blockade (35 t 14 ms vs 32 2 11 ms). The standard deviation of the QT interval across the 12 leads was larger in men than in women at baseline (12.6 ? 4.5 vs 10.8 2 4.1), and this difference was no longer significant after double autonomic blockade (10.4 2 4.4 vs 10.1 ? 3.5). QT dispersion was significantly reduced by autonomic blockade (P < 0.05). Conclusions:(1) Double autonomic blockade slightly reduces QTd. (2) QTd is higher in men than in women at baseline but more similar after autonomic blockade. These findings may contribute to the gender difference in the corrected QT interval. (3) Increased female QTd is not the mechanism of increased female susceptibility to torsade de pointes. The clinical implications of gender differences in QTd and QT, remain to be defined.

Gender Differences in Electrophysiologic Effects of Mental Stress and Autonomic Tone Inhibition:

“…QT dispersion was greater in women during baseline but not significantly so after autonomic blockade. This finding contradicts other reports that found either a greater QT dispersion in men or no difference between men and women 36,37 . Our measurements were made during atrial stimulation; however, when we analyzed QT dispersion during sinus rhythm, women had significantly greater QT dispersion than did men.…”

Estrogen and Progestin Use and the QT Interval in Postmenopausal Women

“…These data suggest that naturally occurring short‐term fluctuations in estrogen and progesterone in premenopausal women do not significantly alter the QT interval. However, the trends seen in our prior data and the lesser QT prolongation response to ibutilide in the luteal phase of the menstrual cycle 22,23 do indicate a possible effect of progesterone on myocardial repolarization.…”

Age, Gender, and Autonomic Tone Effects on Surface Electrocardiographic Indices of Ventricular Repolarization

“…15 In our earlier study, although autonomic blockade reduced QToD, the differences between genders persisted. 16 Aging was associated with a small decrease in QToD in both genders although the difference did not reach statistical significance. While the possibility of a beta error cannot be excluded, aging which prolonged the QTc interval clearly did not prolong QToD.…”