Normalization of QT interval duration in a long QT syndrome patient during pregnancy and the postpartum period due to sex hormone effects on cardiac repolarization

Introduction In inherited long QT syndrome (LQTS), female sex is associated with a longer QT interval duration and a higher risk for potentially lethal polymorphic ventricular tachycardia (pVT) and sudden cardiac death than in males. The arrhythmogenic risk is particularly pronounced during the postpartum period—especially in patients with LQTS type 2—but relatively low during pregnancy, indicating a potential role for sex hormones in modulating cardiac repolarization and arrhythmogenesis in LQTS. In patients with the acquired, drug-induced LQTS variant, hormoneinduced changes in QT interval duration during different phases of the menstrual cycle have been described, with a less pronounced drug-induced QT interval prolongation and hence shorter QT intervals during the luteal phase, when progesterone levels are high, than during the follicular phase with its high estradiol levels. Moreover, postmenopausal hormone replacement therapy in healthy women was found to prolong QT duration in women treated with estradiol alone but did not alter QT duration when combinations of estradiol and progesterone were used. However, despite the use of the heart rate–corrected QTc duration for risk stratification in LQTS patients, to date, the effects of sex hormones and their withdrawal during different phases of menstrual cycle, pregnancy, and postpartum on QT interval duration have not been investigated systematically in patients with inherited LQTS—except for 1 recent report on menstrual cycle–related changes in QT duration in 1 LQTS family.