Long QT Syndrome

Long QT syndrome (LQTS) is a disorder characterized by delayed ventricular repolarization. The condition is associated with sudden cardiac syncope and death due to polymorphic ventricular tachycardia known as torsade de pointes (TdP). Syncope typically occurs during exercise and high emotional load, occurring less frequently at rest or during sleep, and usually without warning. Over 500 mutations in 10 gene have been associated with LQTS in chromosomes 11p15.5 (LQT1), 7q35-36 (LQT2), 3p21-24 (LQT3), 4q25-27 (LQT4), 21q22.1 (LQT5), 21q22.1 (LQT6), 17q23 (LQT7), 12p13.3 (LQT8), 3p25 (LQT9) and 11q23 (LQT10). The genotype of the long QT syndrome influences the clinical course. Beta-adrenergic blockade, sympathetic denervation of the heart and automatic defibrillator are used to prevent ventricular dysrhythmia. Understanding of the molecular processes underlying the syndrome is enabling correspondence between genotype, phenotype and therapy to be established and is leading to better quality of life and survival among sufferers. This review explores the clinical, molecular and epidemiological features of this syndrome. [K]