QT Prolongation 
When this SADR occurs, there is a prolongation of the QT interval on the surface electrocardiogram (ECG), often most evident on the beat(s) just before the onset of the arrhythmia; and basic scientific studies have implicated abnormal cardiac repolarization represented as the QT interval on the surface ECG. Although a series of clinical factors have been identified, the reaction in an individual patient remains unpredictable. The basic electrophysiological mechanisms in this syndrome have been established and provide a series of candidate genes for initiating genomic analysis of risk, as listed below.
