1.0 Introduction
Men and women have several cardiovascular and cardiac electrophysiologic differences. (1). This suggests an important interplay between cardiac physiology and sex hormones. Relevant to this difference, as testosterone levels increase, men experience a shortening of the QT interval (1). QT length is very closely related to arrhythmogenic risk (for instance Torsades de Pointes – TdP), which is why women are at a higher risk than men for developing drug-related TdP, ventricular arrhythmias, drug-induced QT prolongation (DiLQTS) and lethal arrhythmias (2). The QT interval or action potential duration (APD) is defined as the length between the start of the QRS complex (ventricular contraction) and the end of the T wave (ventricular relaxation) shown on ECG. (2,3). As summarized in Figure 1 , the APD is determined by the action of the outward K+ currents and the inward Na+ and Ca2+ currents, which work together to contract and relax the heart through the cardiac cycle (3).