Long QT and Brugada Syndrome

Long QT syndrome (LQTS) and Brugada syndrome are inherited disorders of the heart's ion channels (channelopathies) that can cause sudden cardiac death in young people with a structurally normal heart.

The danger is a sudden ventricular arrhythmia rather than pump failure, so routine structural imaging is often normal. Specialist assessment is still needed to exclude overlapping structural or acquired disease.

The sport and exercise medicine (SEM) clinician meets them through screening, a blackout or palpitations, or a family history of sudden death, and recognises, reads the electrocardiogram (ECG), refers and advises on triggers and medicines.

The heart muscle is normal; the fault lies in the ion channels that generate and reset each heartbeat.

• •LQTS: repolarisation is slowed, so the QT interval is long. This predisposes to torsades de pointes, a polymorphic ventricular tachycardia (VT) that can self-terminate as a blackout or degenerate into cardiac arrest.
• •Brugada syndrome: abnormal sodium-channel function over the right ventricle gives a distinctive pattern in the right chest leads and a risk of ventricular fibrillation (VF).

LQTS is most commonly autosomal dominant, although recessive and syndromic forms exist. Brugada syndrome is often familial, but many affected people have no identifiable single-gene cause; when a variant is found it is usually autosomal dominant with variable penetrance, so many carriers never have an event.

A prolonged corrected QT interval (QTc) is not automatically congenital LQTS. Acquired causes include QT-prolonging medicines, low potassium, magnesium or calcium, a slow heart rate and acute illness. Review and correct these while specialist assessment is arranged.