QTsyndrom

QT syndrome, also known as long QT syndrome (LQTS), is a cardiac channelopathy and repolarization disorder characterized by a prolonged QT interval on the surface electrocardiogram. Prolongation increases the risk of torsades de pointes, a rapid, chaotic form of ventricular tachycardia that can lead to syncope or sudden cardiac death. QT syndrome can be congenital or acquired.

Congenital LQTS results from mutations in genes encoding cardiac ion channels, most notably KCNQ1 (LQT1), KCNH2 (LQT2), and SCN5A (LQT3). These mutations alter potassium or sodium currents, delaying repolarization. Congenital forms include Romano-Ward syndrome (autosomal dominant) and Jervell and Lange-Nielsen syndrome (autosomal recessive, with congenital deafness).

Acquired prolongation can be caused by medications that block potassium channels or by electrolyte disturbances, hypothyroidism, myocardial ischemia, or bradycardia. Triggers include exercise, emotional stress, or sudden intensity changes. Symptoms range from asymptomatic to recurrent syncope, seizures, or sudden death, often precipitated by QTc prolongation.

Diagnosis relies on an ECG showing a prolonged QT interval, corrected for heart rate (QTc). Clinical tools include the Schwartz score and, when indicated, genetic testing to identify the specific mutation. Management focuses on reducing risk: avoidance of QT-prolonging drugs and correctable electrolyte abnormalities; beta-blocker therapy (eg, nadolol or propranolol); in high-risk cases, left cardiac sympathetic denervation or implantable cardioverter-defibrillator may be recommended. Acute torsades requires magnesium sulfate and addressing triggers.

Prognosis depends on subtype and risk factors. With appropriate treatment and lifestyle measures, life expectancy improves, but sudden cardiac events remain a concern. Prevalence is about 1 in 2,000 to 3,000 people for congenital LQTS, with ongoing research into genotype-phenotype correlations and targeted therapies.