Overview
Definition
A disorder of myocardial repolarization characterized by a prolonged QT interval on ECG and an increased risk of Torsades de Pointes.
Epidemiology
Estimated prevalence of 1 in 2,000. Often a cause of unexplained sudden death in the young.
Etiology & Risk Factors
- Mutations in cardiac potassium (KCNQ1, KCNH2) or sodium (SCN5A) channels
- Romano-Ward syndrome (autosomal dominant, purely cardiac)
- Jervell and Lange-Nielsen syndrome (autosomal recessive, associated with sensorineural deafness)
Clinical Symptoms
- Syncope (often triggered by emotional stress, sudden loud noises, or swimming depending on the subtype)
- Seizures (frequently misdiagnosed)
- Sudden cardiac arrest
Clinical Approach
Diagnosis
- ECG: QTc interval > 470 ms (males) or > 480 ms (females)
- Genetic testing for risk stratification
Management
- Beta-blockers (Nadolol or Propranolol) are first-line to blunt the sympathetic response
- Avoid QT-prolonging drugs (e.g., Macrolides, Fluoroquinolones, Antipsychotics, Ondansetron)
- ICD placement for high-risk patients (prior arrest, syncope despite beta-blockers)
- Left cardiac sympathetic denervation (LCSD)
Complications
- Torsades de Pointes (Polymorphic V-Tach)
- Sudden Cardiac Death