Describes an ECG where the ventricular repolarisation (QT interval) is greatly prolonged

Aetiology

• Congenital - Jervell–Lange-Nielsen syndrome (autosomal recessive; associated with deafness), Romano–Ward syndrome (autosomal dominant)
  • Mutation in ion channel results in reduced/dysfunctional ionic current, prolonging cardiac repolarisation and therefore resulting in QT prolongation
  • Triggers for QT prolongation and torsades de pointes include: potassium-rich foods, diarrhoea, vomiting, underwater breath holding, exercise, sudden auditory stimuli, sleep, QT prolonging states
• Acquired - includes electrolyte abnormalities, drugs, diabetes and acute MI
  • Drug triggers include amiodarone, tricyclic antidepressents, antibiotics, fluconazole, erythromycin, metoclopramide, quinidine, haloperidol, ondansetron, SSRIs

Pathophysiology

• A QT interval > 450 ms can lead to prolonged ventricular repolarisation which predisposes to malignant ventricular arrhythmias

Clinical presentation

• Patients with a long QT develop syncope and palpitations as a result of polymorphic ventricular tachycardia (torsades de pointes)
• They usually terminate spontaneously but may degenerate to ventricular fibrillation, resulting in sudden death

Investigations

• ECG and 24 hour tape (QT interval > 450 ms = two large squares)

  

• Echocardiogram to look for structural heart disease

• Genetic testing as required

Management

Acute management of torsades de pointes

• See VT notes

Long term management of congenital QT

• β-blockers - very effective at reducing sudden cardiac death
• Avoid QT prolonging drugs and other triggers
• ICD