Intended for healthcare professionals

Practice Easily Missed?

Long QT syndrome

BMJ 2010; 340 doi: (Published 08 January 2010) Cite this as: BMJ 2010;340:b4815

This article has a correction. Please see:

  1. Dominic J Abrams, consultant cardiologist and electrophysiologist1,
  2. Malcolm A Perkin, general practitioner2,
  3. Jonathan R Skinner, consultant paediatric cardiologist and electrophysiologist3
  1. 1Department of Cardiac Electrophysiology, St Bartholomew’s Hospital and Great Ormond Street Hospital for Children, London
  2. 2Roysia Surgery, Royston
  3. 3Green Lane Paediatric and Congenital Cardiac Services, Starship Children’s Hospital, Auckland, New Zealand
  1. Correspondence to: Dr D J Abrams, Department of Cardiac Electrophysiology, St Bartholomew’s Hospital, London EC1A 7BE d.abrams{at}
  • Accepted 21 October 2009

Case scenario

A 19 year old female student consulted her general practitioner about two recent episodes of syncope, both of which occurred while playing hockey. Her team mates reported that she collapsed suddenly with little warning, recovering rapidly within 30 seconds without confusion. She was otherwise well, although she was taking erythromycin for an infected leg abrasion at the time of the events. As part of the routine evaluation for syncope, her general practitioner performed a 12 lead electrocardiogram, which showed a prolonged corrected QT interval of 510 ms.

Congenital long QT syndrome is a potential cause of avoidable sudden cardiac death. Affected individuals may have ventricular arrhythmias, leading to palpitations, syncope, and, if sustained, cardiac arrest.1 The syndrome is inherited in an autosomal dominant fashion, with variable disease expression: those severely affected may die in fetal or neonatal life, but others remain asymptomatic throughout their life. At a cellular level, genetically encoded abnormalities in sodium and potassium ion channels within the cell membrane lengthen cardiac repolarisation, which manifests as a prolongation of the QT interval in the electrocardiogram. QT prolongation may be acquired secondary to certain medications, metabolic disturbance, cerebral injury, myocardial disease, and hypothermia—factors that may also unmask the congenital syndrome in a previously asymptomatic individual.

How common is long QT syndrome?

  • The exact prevalence of long QT syndrome in the population is unknown as disease expression may be highly variable

  • Current population estimates range from 1 in 20002 to 1 in 30003

  • Most general practices in the UK are likely therefore to have at least one patient with the condition

Why is long QT syndrome missed?

Syncope is highly prevalent in young adults. Among 394 students, 154 reported at least one episode of syncope.4 In a young, fit adult (such as outlined in the scenario box), important differential diagnoses include the most common and benign cause of …

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