Long QT syndrome
A genetic disorder of cardiac ion channels causing prolonged ventricular repolarization and risk of sudden death.
Full Definition
Long QT syndrome (LQTS) is a hereditary channelopathy characterized by prolonged ventricular repolarization manifesting as a prolonged QT interval on the ECG (typically >480 ms in repeated measurements). The condition is caused by mutations in genes encoding cardiac ion channels, with over 15 different genetic subtypes identified. The three most common forms are LQT1 (KCNQ1), LQT2 (KCNH2), and LQT3 (SCN5A), each with distinct triggers and treatment responses. Patients are at risk for torsades de pointes, a polymorphic ventricular tachycardia that can degenerate into ventricular fibrillation and sudden cardiac death. Symptoms include syncope, seizures, or cardiac arrest, often triggered by exercise (LQT1), sudden loud noises (LQT2), or during sleep (LQT3). Treatment includes beta-blockers, lifestyle modifications, and implantable cardioverter-defibrillators in high-risk cases.
Usage
Usage note: Commonly abbreviated as LQTS; specify genetic subtype when known for treatment planning.
In Context
- "Genetic testing confirmed Long QT syndrome type 1 in the patient with exercise-induced syncope." — Genetic counseling report
- "The corrected QT interval of 520 ms raised suspicion for LQTS and prompted family screening." — Electrophysiology consultation