- Patients meet any one of the following heart standard: in static State, 3 times ECG check shows average correction QT period (QTc) >470 msec; clinical abnormal symptom of rhythm, conduction, and static ECG, for example completely left beam conduction block, III degrees conduction block, II degrees conduction block, PR period >250 msec, various factors with risks of extended QTc or rhythm disorders, for example, congestive heart failure, low potassium blood syndrome, congenital long QT Syndrome, direct relatives has long QT syndrome or sudden unexplained death in less than 40 years old, drug combination that may prolong the QT interval.