Cardiac repolarization in recently postmenopausal women with or without hot flushes.

Objective: Menopausal hot flushes are associated with elevated activity of the sympathetic nervous system and may be related to increased risk for cardiovascular events. Sympathetic activation may trigger severe arrhythmias by modulating cardiac repolarization. The aim of this study was to evaluate the impact of hot flushes on cardiac repolarization in postmenopausal women with and without hot flushes. Methods: We assessed 150 recently postmenopausal healthy women-72 with hot flushes and 78 without hot flushes. They underwent 24-hour electrocardiographic recording, comprising a total of over 10,000,000 QT-interval measurements. The cardiac repolarization was assessed by measuring QT-intervals, heat rate dependence of QT-end intervals, and T-waves. Results: The maximal QT-end interval was shorter in women with hot flushes compared with those without hot flushes (481 +/- 64 ms vs 493 +/- 50 ms; P = 0.046). There were no differences between the rate dependence of QT-end intervals and T-wave measures between the groups. During the night-time hot flush period, we detected a steeper rate-dependence of QT-end intervals and a longer maximal T-peak-T-end interval (117 +/- 54 ms vs 111 +/- 56 ms; P < 0.001) compared with the control period. Conclusions: Women with hot flushes did not have clinically significant differences in ambulatory cardiac repolarization measurements compared with asymptomatic women. However, a sudden sympathetic surge occurring during the night-time hot flush may have direct effects on cardiac repolarization.