QT prolongation
Also calledprolonged QT · prolonged QTc · QTc prolongation · long QTc
Definition
A QT interval (rate-corrected as QTc) that exceeds normal limits; the 2009 AHA/ACCF/HRS statement treats a QTc of 450 ms or longer in men and 460 ms or longer in women as prolonged, and a QTc above 500 ms is associated with a 2- to 3-fold higher risk of torsades de pointes. It is a descriptive ECG finding of abnormal ventricular repolarization that may be congenital or acquired, for example from QT-prolonging drugs, hypokalemia or hypocalcemia; hypomagnesemia and bradycardia add to the risk of torsades de pointes.
Clinical noteThis is a descriptive finding, not a diagnosis. Normal limits vary by source: a 2010 AHA/ACCF statement puts the 99th percentile at about 470 ms in men and 480 ms in women.
Sources
- Rautaharju PM, Surawicz B, Gettes LS. AHA/ACCF/HRS recommendations for the standardization and interpretation of the electrocardiogram: part IV: the ST segment, T and U waves, and the QT interval. Circulation. 2009;119(10):e241-e250. doi.org/10.1161/CIRCULATIONAHA.108.191096
- Drew BJ, Ackerman MJ, Funk M, et al. Prevention of torsade de pointes in hospital settings: a scientific statement from the American Heart Association and the American College of Cardiology Foundation. Circulation. 2010;121(8):1047-1060. doi.org/10.1161/CIRCULATIONAHA.109.192704
Last reviewed 2 October 2026. Every definition in the EKG Dictionary cites the guideline, consensus statement or original paper it comes from.