Medical Minute: Long QT Syndrome Pearls

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July 15, 2014 by dailybolusoflr

By Lisa Cuttle, MD

Quick review: 

• Channelopathy
• Definition is QTc > 460 in men, 470 in women
• Often see notched or bifid T waves, although these may not be present at rest. 
• Estimated incidence about 1/2500 births, although likely underestimated.

1. There are multiple different formulas* to calculate QTc which you should use if you are concerned, don’t just use QTc on EKG.

*Bazett’s formula most common: QTc = QT interval ÷ √RR interval (in sec).

2. Syncope in long QT syndrome is aborted sudden death. Be very cautious about syncopal episodes in the pediatric population, or in those without prodrome or with associated facial trauma which indicates sudden onset.

3. Though sometimes easy to gloss over, family history is especially important as there is a strong genetic component. Make sure to ask about sudden deaths, drownings, single person MVC’s, or SIDS in the family.

4. If suspected, cardiology consult in ED is warranted, may be able to start beta-blocker therapy, and patients should have close follow up.

5. Advise patients to avoid QT prolonging meds, dehydration, sudden startling noises, and fever as these can provoke torsades/sudden death.

Sources:

1. http://www.uptodate.com/contents/diagnosis-of-congenital-long-qt-syndrome?source=machineLearning&search=long+qt&selectedTitle=2%7E150&sectionRank=1&anchor=H2#H2

2. White, J. Demystifying the Congentital Long QT Diagnosis. EP Monthly 2014; Vol 21, 6:26. http://www.epmonthly.com/features/current-features/demystifying-the-congenital-long-qt-diagnosis/