Menstrual cycle and ST height

Background: Sex hormones and menstrual cycle effects on ST height have not yet been clearly identified. Methods: Twenty-two young, healthy women (aged 22-32 years) were included in this study. Twelve-lead ECGs were registered during menses, follicular and luteal phase of the menstrual cycle at baseline, and after double autonomic blockade (DAB). Chest leads V2-V4 and limb leads I and II were chosen for analysis. ST height was measured manually at J-Point and 40 ms after the J-Point, and values were corrected for QRS amplitude (J-Point/QRS, 40 ms/QRS). Repeated measure ANOVA was used to analyze differences in ST height among the three phases of the menstrual cycle. A P-value < 0.05 was considered as significant. Results: At baseline, ST height, QTc, and T wave amplitude were not significantly different among the three phases of the menstrual cycle. After double autonomic blockade, ST height at 40 ms, J-Point/QRS, and 40 ms/QRS was significantly higher during follicular versus luteal phase (0.152 ± 0.413 mm versus -0.007 ± 0.427 mm, P = 0.0059 at 40 ms; -0.001 ± 0.030 versus -0.015 ± 0.032, P = 0.0039 at J-Point/QRS; 0.013 ± 0.031 versus -0.004 ± 0.032, P = 0.0005 at 40 ms/QRS) as was the QTc. ST height differences at J-Point were not significantly different (-0.046 ± 0.395 mm follicular, -0.167 ± 0.448 mm luteal, and -0.083 ± 0.492 mm menses, P = 0.1014). Conclusion: ST height and QTc varied among the three phases of the menstrual cycle, predominantly after double autonomic blockade. Female sex hormones that vary throughout the menstrual cycle may modulate measures of repolarization.