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Long QT Interval

Henry DeYoung, MD, Yousef Ahmed, MD and Derek Lodico, DO Reviewed 06/2018
 


BASICS

DESCRIPTION

  • QT interval: the measurement interval from the beginning of the QRS complex to the end of the T wave on the surface electrocardiogram (ECG). This represents the period from the onset...

DIAGNOSIS

HISTORY

  • Incidental finding on ECG in asymptomatic patients

  • Evaluate for syncope, presyncopal episodes, palpitations, and associated precipitating events (emotional triggers, swimming, diving).

  • ...

TREATMENT

GENERAL MEASURES

  • Treat VT, TdP, and VF emergently per ACLS guidelines.

  • Withdraw offending agents and correct electrolytes.(2)[C].

  • Transvenous cardiac pacing or isoproterenol may be used for dru...

ONGOING CARE

FOLLOW UP RECOMMENDATIONS

On routine visits, ask about syncope, presyncope, and palpitations in those who have QTc prolongation. 
  • Consider ECG and/or outpatient cardiac rhythm monitoring wi...

REFERENCES

1
Kramer DB, Zimetbaum PJ. Long-QT syndrome. Cardiol Rev.  2011;19(5):217–225.
2
Kallergis EM, Goudis CA, Simantirakis EN, et al. Mechanisms, risk factors, and management of acquired long...

ADDITIONAL READING

  • Drug and Therapeutics Bulletin. QT interval and drug therapy. BMJ.  2016;353:i2732.

  • Fortescue EB. A piece of my mind. Keeping the pace. JAMA.  2014;311(23):2383–2384. [Vie...

SEE ALSO

Algorithms: Cardiac Arrhythmias; Torsade de Pointes (TdP): Variant Form of Polymorphic Ventricular Tachycardia (VT) 

CODES

ICD10

I45.81 Long QT syndrome 

ICD9

426.82 Long QT syndrome 

SNOMED

  • 9651007 Long QT syndrome (disorder)

  • 442946007 Aquired long QT syndrome

  • 442917000 Congenital long QT syndrome

CLINICAL PEARLS

  • Evaluate for acquired causes before making a diagnosis of hereditary LQTS.

  • For accurate diagnosis, calculate QTc manually.

  • The ideal management of TdP is prevention; avoid multiple “stac...

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