Sex differences in QT interval variability and implication on sample size of thorough QT study

Clinical and experimental studies show that differences exist in cardiac electrophysiology between women and men, especially in electrocardiographical patterns of ventricular repolarization. We examined the variability of QT intervals from two thorough QT/QTc clinical studies, one conducted in a male population and one conducted in a female population. The results show variability differences in QT measurements between males and females, with females having larger intersubject and intrasubject variability than males. This article presents those results as well as discusses the implications for sizing thorough QT/QTc studies when studies include a mixture of men and women.