what are the upper limits of normal for the qtc
QT interval Definitions of normal QTc vary from being equal to or less than 0.40 s (≤400 ms),[9] 0.41s (≤410ms),[10] 0.42s (≤420ms)[11] or 0.44s (≤440ms).[12] For risk of sudden cardiac death, "borderline QTc" in males is 431–450 ms; and, in females, 451–470 ms. An "abnormal" QTc in males is a QTc above 450 ms; and, in females, above 470 ms.[13]