Long QT syndrome (LQTS) and Brugada syndrome are inherited disorders of the heart's electrical system, known together as channelopathies because they arise from faults in the ion channels that control the cardiac electrical signal. They are primarily electrical disorders, so routine structural imaging is often normal, and the danger is a sudden, life-threatening arrhythmia rather than mechanical pump failure. Specialist assessment is still needed to exclude overlapping structural or acquired disease. Both are recognised causes of sudden cardiac death (SCD) in young people and athletes, which places them in the sport and exercise medicine (SEM) field.
For the SEM doctor and the wider musculoskeletal (MSK) team, these conditions are met through screening, through an athlete who reports a blackout or palpitations, often in a particular situation, or through a family history of sudden death. The role is to recognise the warning patterns, interpret the electrocardiogram sensibly, refer, and give clear advice on triggers, medication and activity.
The heart muscle itself is normal; the problem lies in the ion channels that generate and reset the electrical signal in each heartbeat. Long QT syndrome is most commonly inherited in an autosomal dominant pattern, although recessive and syndromic forms exist. Brugada syndrome is often familial, but many clinically affected people have no identifiable single-gene cause; when a pathogenic variant is found it is usually autosomal dominant, with variable penetrance, so many carriers never have an event.
In LQTS, the channels that reset the heart, a process called repolarisation, work too slowly, so the recovery phase of the heartbeat is prolonged. On the electrocardiogram this shows as a long QT interval, and it predisposes to a characteristic polymorphic ventricular tachycardia (VT) called torsades de pointes, which can stop the heart or self-terminate as a blackout. Different genetic subtypes have different triggers: some events occur with exertion, classically swimming, others with sudden emotion or noise, and others at rest or during sleep.
In Brugada syndrome, abnormal sodium-channel function disturbs the electrical signal over the right ventricle, producing a distinctive pattern in the right-sided chest leads and a risk of ventricular fibrillation (VF). Events often happen at rest or during sleep, and fever is a particularly important trigger, which is relevant to any athlete with an intercurrent illness.
A prolonged corrected QT interval is not automatically congenital LQTS. Reversible and acquired causes include QT-prolonging medicines, a low potassium, magnesium or calcium, a slow heart rate and acute illness, and these should be reviewed and corrected while specialist assessment is arranged.
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