Long QT syndrome (LQTS)

 

Clinical features

  1. LQTS is a group of familial conditions that is an important cause of unexpected sudden death, especially in children and young adults.
  2. LQTS most commonly presents with syncope and sudden death during or following exercise in otherwise fit and health young people.
  3. Cardiovascular manifestations include:
  4. Prolonged QT interval on ECG
  5. Syncope
  6. Ventricular fibrillation
  7. Rapid ventricular tachycardia
  8. Sudden cardiac death
  9. Symptoms usually develop during childhood, but may occur at any age.
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Genetics

  1. LQTS is a group of ion channel conditions. Abnormal function of cardiac ion channels lead to cardiac arrhythmias.
  2. At least eight genes are known to be involved.
  3. Two major clinical syndromes with LQTS have been characterised on the basis of the pattern of inheritance:
  4. The more common autosomal dominant form with a pure cardiac phenotype (Romano-Ward syndrome)
  5. A rarer autosomal recessive form characterised by the co-existence of cardiac abnormalities and congenital deafness and especially long QT intervals (Jervell and Lange-Nielsen variant)
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Prevalence

  1. Prevalence is around 1 in 5000.
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Management

  1. Refer to cardiologist for clinical cardiac assessment, involving ECG and exercise tests.
  2. Genetic testing results can help guide management, particularly in asymptomatic at risk relatives. Refer to Genetics Services to discuss the availability and value of genetic testing (see Contacts, support and testing).
  3. Treatment of choice for most individuals with LQTS is drug therapy with beta-adrenergic blockers. Beta blockers may be used prophylactically for gene-positive asymptomatic children and adults.
  4. Treatment with an implantable automatic cardioverter-defibrillator (ICD) may be indicated for some individuals. ICDs can be used in conjunction with anti-arrythmic drug therapy.
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