• Clinical science

Long QT syndrome

Abstract

Long QT syndrome (LQTS) is a congenital or acquired heart condition in which the QT interval (i.e., ventricular depolarization and repolarization) is prolonged. Most patients with LQTS are asymptomatic, but some present with seizures, syncope, or even life-threatening arrhythmias and sudden death. Treatment depends on the underlying cause: Beta blockers and implantable cardioverter defibrillator (ICD) insertion are commonly used for congenital LQTS, whereas treatment of the underlying cause (drug, electrolyte abnormality, etc.) is the first-line therapy for acquired LQTS.

Etiology

A prolonged QT interval may be congenital or acquired.

Congenital LQTS

Acquired LQTS

References:[5][6][7][8][9][10][11]

Clinical features

  • Often asymptomatic, especially if the QT interval is only minutely prolonged
  • Some patients present with:
    • Palpitations
    • Dizziness
    • Syncope
    • Cardiac arrest

References:[5]

Diagnostics

Finding Score
History Congenital deafness 0.5
Family history of LQTS 1
Family history of sudden cardiac death 0.5
Syncope 1 (without stress) or 2 (with stress)
ECG 460–469 ms 2
450– 459 ms 1
Torsade de pointes 2
T-wave alternans 1
Notched T wave in 3 leads 1
Bradycardia 0.5
  • Genetic testing confirms the diagnosis of LQTS.

References:[6][12]

Treatment

  • Both congenital and acquired LQTS
    • Avoid activities that stress the heart
    • Avoid cold temperatures (e.g., swimming, diving, skiing)
  • Congenital LQTS
  • Acquired LQTS: treat cause; (remove offending drug, fix electrolyte imbalances, etc.)

All treatment modalities aim to reduce the risk and severity of cardiac events!

References:[6]

Complications

References:[13]

We list the most important complications. The selection is not exhaustive.