Difference between revisions of "QT prolongation"

(Clinical Features)
(Clinical Features)
Line 13: Line 13:
**[[Cardiac arrest]]
**[[Cardiac arrest]]
**Family history of long QT or sudden death
**Family history of long QT or sudden death
**Medication history should always be obtained especially so to avoid interactions and further QT prolongation
*Medication history may include QT prolonging medications
==Differential Diagnosis==
==Differential Diagnosis==

Revision as of 20:18, 7 March 2019


  • Prolonged ventricular repolarisation → increased risk of ventricular arrythmias
    • Males >440-450 ms
    • Females >500 ms
    • Rule of thumb: Normal QT interveal is less than half of preceding RR interval
  • QT interval is from the beginning of the Q wave to the end of the T wave
    • Rate dependent and should become proportionately shorter with increasing heart rate

Clinical Features

  • Most are asymptomatic
  • History may include:
  • Medication history may include QT prolonging medications

Differential Diagnosis

Drug List


  • ECG
    • quick/imprecise measure: QT takes up more than half the R-R distance
    • Measure QT interval in lead II or V5-6
    • QTc = QT /√R-R
    • Long QT: QTc >440 (male), >460 (female)
    • >500 = real concern (may result in torsades)


Pause Dependent (precipitated by bradycardia)

Adrenergic Dependent (precipited by tachycardia)


  • Highly consider admission, especially for QT >500

See Also

External Links