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

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.1,2 The arrhythmogenic risk is particularly pronounced during the postpartum period—especially in patients with LQTS type 2—but relatively low during pregnancy,3 indicating a potential role for sex hormones in modulating cardiac repolarization and arrhythmogenesis in LQTS. In patients with the acquired, drug-induced LQTS variant, hormone-induced 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.