Difference between revisions of "QT prolongation"

(Disposition)
(Evaluation)
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==Evaluation==
 
==Evaluation==
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===Workup===
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*[[ECG]]
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*CBC
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*Chem 10
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===Diagnosis===
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[[File:De-Acquired longQT (CardioNetworks ECGpedia).jpg|thumb|Acquired QT prolongation]]
 
*[[ECG]]
 
*[[ECG]]
 
**On visual inspection, QT takes up more than half the R-R distance
 
**On visual inspection, QT takes up more than half the R-R distance

Revision as of 12:59, 30 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 include:
  • Medication history may include QT prolonging medications

Differential Diagnosis

Drug List

Evaluation

Workup

  • ECG
  • CBC
  • Chem 10

Diagnosis

Acquired QT prolongation
  • ECG
    • On visual inspection, QT takes up more than half the R-R distance
    • Measure QT interval in lead II or V5-6
    • QTc = QT /√R-R

Management

Pause Dependent (precipitated by bradycardia)

Adrenergic Dependent (precipited by tachycardia)

Disposition

  • Consider admission, especially for QT >500 or if symptomatic
  • May require consultation for discontinuation of QT prolonging medications
  • Avoid prescribing medications that may contribute to prolonged QT

See Also

External Links

References