Difference between revisions of "QT prolongation"

(Background)
(Background)
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==Background==
 
==Background==
 
*Prolonged ventricular repolarisation → increased risk of ventricular arrythmias
 
*Prolonged ventricular repolarisation → increased risk of ventricular arrythmias
*QT interval is from the beginning of the Q wave to the end of the T wave; it is rate dependent and should become proportionately small with increasing rate rate
+
**Males >440-450 ms
*An abnormal QT is >440-450 ms (males) and >460-470 ms (females); >500 may result in [[torsades]]
+
**Females >500 ms
*A useful rule of thumb is that a normal QT is less than half the preceding RR interval
+
**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==
 
==Clinical Features==

Revision as of 20:15, 7 March 2019

Background

  • 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 or may not include
    • Syncope, cardiac arrest, family history of long QT or sudden death
    • Medication history should always be obtained especially so to avoid interactions and further QT prolongation.

Differential Diagnosis

Drug List

Evaluation

  • 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)

Management

Pause Dependent (precipitated by bradycardia)

Adrenergic Dependent (precipited by tachycardia)

Disposition

  • Highly consider admission, especially for QT >500

See Also

External Links

References