Congenital Long-QT Syndromes

Abstract

The congenital long-QT syndromes (LQTS) were initially described approximately 50 years ago.1–3 The principal events are syncope, seizures, and ventricular tachycardia, characteristically torsade de pointes. Most often, this arrhythmia is self terminating, producing a syncopal episode; however, LQTS is responsible for a significant proportion of sudden cardiac deaths (SCDs) in young people without structural heart disease, estimated to have an incidence of approximately 1 in 2500 and causing thousands of deaths annually.4–6 Characteristic ECG signs of LQTS include QT-interval prolongation and T-wave abnormalities. The heart rate–corrected QT interval (QTc) can range from 370 to >700 ms, clearly overlapping that of normal individuals, and a single ECG may not manifest the stereotypical features.7–9 Some patients have a normal or borderline QTc at rest but prolongation with exertion or β-adrenergic stimulation. Provocative testing with exercise or catecholamine infusion may improve the sensitivity of LQTS clinical detection.9–11 The inciting triggers are somewhat mutation-specific. Patients with potassium channel mutations typically have episodes during physical or emotional stress, whereas those with sodium channel defects have more events with bradycardia and during sleep.12–15 Symptoms, including syncope or SCD, can manifest anytime from the neonatal period to adulthood. Because risk stratification is still being refined, it is often recommended that most LQTS patients be treated with β-adrenergic blocking medications, but a diagnostic challenge is deciding who needs more specific or aggressive therapies. Interventions for LQTS include implantation of a permanent pacemaker or implantable cardioverter defibrillator (ICD), as well as consideration of left cardiac sympathetic denervation. If interventional therapy is warranted, what procedures are right for which patients, and when is the optimal time to intervene?16 The competing risks of the disease versus potential complications from the procedures or devices often increase the complexity of the clinical decision-making rationale. Articles p 2184 …