Correct QT interval for heart rate using multiple formulas.
Bazett: QTc = QT / √RR. Fridericia: QTc = QT / RR^(1/3). Framingham: QTc = QT + 154×(1−RR). Bazett overestimates at high HR and underestimates at low HR. Fridericia is preferred for pharmacological studies. Normal QTc: ≤440 ms (men), ≤460 ms (women). QTc > 500 ms significantly increases risk of torsades de pointes.