Physiological mechanisms influencing cardiac repolarization and QT interval

Cardiac repolarization primarily results from activation of outward currents carried by potassium ions which are heterogenously distributed throughout the myocardial layers which can lead to changes in various phases of cardiac cycle. QT interval is a reflector of cardiac repolarization and can be influenced by heart rate, autonomic nervous system, gender and time of the day. T wave alternans (TWA), specifically the discordant pattern is a feature of abnormal cardiac repolarization that can be used as a predictor of ventricular arrhythmias.