gms | German Medical Science

Objectives: The aim of this study was to investigate the effects of the menstrual cycle on QT interval dynamics and the autonomic tone in healthy women.

Methods: Holter ECGs were recorded in 11 healthy female wolunteers aged 18 to 32 years during the follicular- and luteal phases of their regular menstrual cycle. Two QT parameters, the interval from QRS onset to the apex (QaT) and to the end of the T wave (QeT), the interval between the apex and the end of the T wave (Ta-e), and RR intervals were measured automatically in the course of 24 hr by Holter ECGs (QT guard, GE Medical systems). The QeT/RR, QaT/RR, and Ta-e/RR relationships were evaluated in each subject. The autonomic tone was assessed by serum catecholamine level at rest and heart rate variability measured by Holter ECGs. Results: (1) The follicular and luteal phases did not differ significantly with respect to the slopes of the QeT/RR, QaT/RR, and Ta-e/RR relationships. However, QeT and QaT intervals were significantly shorter for all RR intervals in the luteal- than the follicular phase (p<0.0001). (2) The serum progesterone concentration was significantly higher in the luteal- than follicular phase (p<0.001). (3) Noradrenaline was significantly higher in the luteal- than follicular phase (p<0.05). There was no significant difference in the follicular- and luteal phase with respect to heart rate variability measurements.

Conclusions: Our results suggest that the menstrual cycle affects the QT interval dynamics. The observed shorter QT interval during the luteal- than follicular phase may be attributable to the increase in serum progesterone and sympathetic tone during the luteal phase.