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[Feature] Corrected QT interval [Pathology] A prolonged QTc interval is a risk factor for ventricular tachyarrhythmias and sudden death. Long QT can arise as a genetic syndrome, or as a side effect of certain medications. An unusually short QTc can be seen in severe hypercalcemia. [Duration] <440 ms [Description] 
The QT interval is measured from the beginning of the QRS complex to the end of the T wave. Acceptable ranges vary with heart rate, so it must be corrected by dividing by the square root of the RR interval.
Electrocardiography - Wikipedia, the free encyclopedia