- QTc with Bazett s correction that is unmeasurable, or >470 msec on screening ECG. (Note: If a subject has a QTc interval >470 msec on screening ECG, the screen ECG may be repeated twice (at least 24 hours apart). The average QTc from the three screening ECGs must be less than or equal to 470 msec in order for the subject to be eligible for the study. Patients who are receiving a drug that has a risk of QTc prolongation excluded if QTc is greater than or equal to 460 msec.