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

Background Although gender differences in the corrected QT interval (QTc) 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 (maximum — minimum QT) was larger in men than in women at baseline (41 ± 17 ms vs 35 ± 16 ms), and this difference tended to decrease after double autonomic blockade (35 ± 14 ms vs 32 ± 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 ± 4.1), and this difference was no longer significant after double autonomic blockade (10.4 ± 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 QTc remain to be defined. A.N.E. 1998; 3(1):25–31