Aims: Women have a longer QT interval and a greater incidence of torsades de pointes than men. It has been suggested that oestrogens may influence the duration of cardiac repolarization. We thus investigated the influence of oestradiol (E2) on ventricular repolarization within the physiological concentration range of this hormone.
Methods and results: We studied QT interval duration in 21 healthy women aged 18 to 35 years with regular menstrual cycle (mean duration: 29+/-1 days) during two periods associated with a wide range of oestradiol plasma levels: low level during menses (105+/-34 pmol/l) and high level during the pre-ovulatory phase (750+/-277 pmol/l). We used heart rate-independent assessment of QT. QT-RR pairs were measured over a wide range of RR intervals obtained at rest and during a sub-maximal exercise test. Using a monoexponential nonlinear curve fitting for the QT-RR relation, the QT(1000 ms)during nadir and peak oestradiol periods was then determined for each subject. QT(1000 ms)interval was not different between both study periods: 382.1+/-18.4 ms at peak versus 382.2+/-19.4 ms at nadir oestradiol level (P=0.98).
Conclusion: No significant change in QT interval duration was observed within the large range of physiological E2 variations found during the menstrual cycle.