Long QT syndrome

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Last reviewed: 28 Aug 2022
Last updated: 10 Jun 2021

Summary

Definition

History and exam

Key diagnostic factors

  • history of known gene mutation
  • use of drugs or circumstances known to increase the QT interval
  • syncope during heightened adrenergic tone
  • syncope during arousal or surprise
  • arrhythmic symptoms post partum
  • syncope at rest and during bradycardia
  • cardiac syncope
  • palpitations
  • periodic paralysis
  • dysmorphic features
  • sensorineural deafness
More key diagnostic factors

Other diagnostic factors

  • dizziness
  • angina
  • fatigue
  • oliguria
  • muscle weakness
  • tetany
  • numbness
  • Chvostek's sign
  • Trousseau's sign
  • cold and pale extremities
  • hypotension
  • confusion
Other diagnostic factors

Risk factors

  • KCNQ1 gene mutations
  • KCNH2 gene mutations
  • SCN5A gene mutations
  • QT interval-prolonging drugs
  • hypokalaemia
  • hypomagnesaemia
  • hypocalcaemia
  • bradyarrhythmias
  • central nervous system lesions
  • female sex
  • malnutrition
More risk factors
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Diagnostic investigations

1st investigations to order

  • ECG for LQT1
  • ECG for LQT2
  • ECG for LQT3
  • ECG for hypokalaemia and hypomagnesaemia
  • ECG for hypocalcaemia
  • ECG for complete atrioventricular (AV) block
  • serum potassium
  • serum magnesium
  • serum calcium
More 1st investigations to order

Investigations to consider

  • Holter monitor
  • exercise tolerance test
  • echocardiography
  • genetic testing
  • adrenaline (epinephrine) test
More investigations to consider
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Treatment algorithm

ACUTE

acquired LQTS without previous cardiac event

congenital LQTS without previous cardiac event

acquired LQTS with previous cardiac event

congenital LQTS with previous cardiac event

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Contributors

Authors

Mehmet K. Aktas, MD, MBA

Associate Professor of Medicine

University of Rochester Medical Center

Rochester

NY

Disclosures

MKA declares that he has received research support from Medtronic and Biosense Webster. He is the author of a reference cited in this topic.

James P. Daubert, MD

Professor of Medicine

Duke University Medical Center

Duke Clinical Research Institute

Durham

NC

Disclosures

JPD declares that he has received honoraria for advisory boards, data safety monitoring boards, events committees, or lecture fees from Abbott, Biosense Webster, Biotronik, Boston Scientific, Farapulse, Gilead Sciences Inc., Medtronic, Microport, Phillips, Vytronus, and ZOLL; and research grants from Abbott and Medtronic. JPD declares that he has no stock, stock options, or other forms of ownership. He is the author of a reference cited in this topic.

Peer reviewers

Sami Viskin, MD

Director of Cardiac Hospitalization

Department of Cardiology

Tel Aviv Medical Center

Tel Aviv

Israel

Disclosures

SV declares that he has no competing interests.

Elizabeth S. Kaufman, MD

Associate Professor

Heart and Vascular Center

MetroHealth Campus

Case Western Reserve University

Cleveland

OH

Disclosures

ESK declares that she has no competing interests.

  • Long QT syndrome images

  • Differentials

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    • Neurological syncope
    More Differentials

  • Guidelines

    • Guidelines for the diagnosis and management of syncope
    • 2017 AHA/ACC/HRS guideline for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death
    More Guidelines

  • Patient leaflets

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    What you can do to prevent another heart attack

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  • Calculators

    QT Interval Correction

    More Calculators
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