The normal QT interval is controversial, and multiple normal durations have been reported. In general, the normal QT interval is below 400 to 440 milliseconds (ms), or 0.4 to 0.44 seconds.

Although a normal QT interval imparts ... had a prolonged QT interval (over 440–470 ms in men, over 460–480 ms in women), or were carriers of a known genetic mutation (regardless of their QTc).

The absolute QT interval on this ECG is approximately 640 ms which is quite long, but the QTc when accounting for the slow heart rate is about 380 ms which is normal. This is why the "corrected QT ...