- ECG measurements: QTc(F)<450 msec or QTc(F)<480 msec for patients with bundle branch block. The QTc is the QT interval corrected for heart rate according to either Bazett's formula (QTcB), Fridericia's formula (QTcF), or another method, machine or manual overread. For subject eligibility and withdrawal decisions, QTcFwill be used. For purposes of data analysis, QTcF will be used as primary though data using both correction formulas will be collected and analysed. The QTc should be based on single or averaged QTc values of triplicate electrocardiograms (ECGs) obtained over a brief recording period.