Last reviewed: June 2019
Last updated: January  2018

Summary

Definition

History and exam

Key diagnostic factors

  • hx 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
Full details

Other diagnostic factors

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

Risk factors

  • KCNQ1 gene mutations
  • KCNH2 gene mutations
  • SCN5A gene mutations
  • QT interval-prolonging drugs
  • hypokalaemia
  • hypomagnesaemia
  • hypocalcaemia
  • bradyarrhythmias
  • CNS lesions
  • female sex
  • malnutrition
Full details

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 AV block
  • serum potassium
  • serum magnesium
  • serum calcium
Full details

Investigations to consider

  • Holter monitor
  • exercise tolerance test
  • echocardiography
  • genetic testing
  • adrenaline (epinephrine) test
Full details

Treatment algorithm

ACUTE

acquired LQTS without previous cardiac event

congenital LQTS without previous cardiac event

acquired or congenital LQTS with previous cardiac event

Contributors

Authors VIEW ALL

Associate Professor of Medicine

University of Rochester Medical Center

Rochester

NY

Disclosures

MKA declares that he has no competing interests.

Director

Electrophysiology Service

Professor of Medicine

Duke University Medical Center

Duke Clinical Research Institute

Durham

NC

Disclosures

JPD is a consultant for the American College of Cardiology, ARCA Biopharma, Biosense Webster, Biotronik, Boston Scientific, Cardiofocus, Gilead Sciences Inc., Medtronic Inc., NIH-NHLBi, Northwestern University, Orexigen Therapeutics Inc., St. Jude, and Vytronus.

Peer reviewers VIEW ALL

Director of Cardiac Hospitalization

Department of Cardiology

Tel Aviv Medical Center

Tel Aviv

Israel

Disclosures

SV declares that he has no competing interests.

Associate Professor

Heart and Vascular Center

MetroHealth Campus

Case Western Reserve University

Cleveland

OH

Disclosures

ESK declares that she has no competing interests.

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