Brugada syndrome

Definition

Brugada syndrome is an inherited channelopathy with characteristic ECG changes in the right precordial leads (prominent J wave, coved ST elevation and inverted T wave in V1–V3). It increases the risk of ventricular tachycardia and ventricular fibrillation with syncope and sudden cardiac death, typically without clinically evident structural heart disease.

Classification

ECG patterns

• Type 1 pattern: prominent J-point and ST elevation in V1 and V2 (sometimes V3) resembling right bundle branch block; the ST segment is coved and descends into an inverted T wave. Only a spontaneous type 1 pattern is considered diagnostic.
• Type 2 and type 3 patterns: less pronounced and not diagnostic; they may change to a type 1 pattern spontaneously, with fever or in response to drugs.
• Scores (Shanghai score) incorporating clinical, family and genetic criteria have been developed for borderline cases.

Occurrence & epidemiology

The frequency is about 5 per 10,000 people, with wide variation by ethnicity and region. 80–90 % of clinically affected people are male. In young men Brugada syndrome may account for up to about one third of sudden cardiac deaths.

Aetiopathogenesis

The cause is mutations that reduce inward sodium or calcium currents or increase early outward potassium currents. This leads to early loss of the action potential plateau, particularly in the epicardial cells of the right ventricular outflow tract. Most known mutations affect the SCN5A gene (loss of function of the sodium channel). Microscopic structural abnormalities in the epicardium of the outflow tract are often present; overlap with LQTS type 3, early repolarization syndrome and arrhythmogenic right ventricular cardiomyopathy has been described.

Triggers of arrhythmias: fever and certain drugs (sodium channel blockers, some antidepressants and antipsychotics, lithium) as well as alcohol and cocaine.

Clinical features

Most affected people are asymptomatic. In some, polymorphic VT or ventricular fibrillation causes syncope or sudden cardiac death, often at night during sleep and usually not with exercise. About 10–20 % develop atrial tachyarrhythmias, mainly atrial fibrillation, which may also be the first manifestation.

Diagnosis

• Suspicion in unexplained cardiac arrest or syncope, or a corresponding family history, without structural heart disease
• ECG: detection of the type 1 pattern; recording V1 and V2 additionally from the second and third intercostal spaces increases sensitivity
• Pharmacological provocation test with a sodium channel blocker to unmask a type 1 pattern; an ECG during fever may also reveal the pattern
• Genetic testing: yield about 20 %; evaluation of family members

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Further reading (open access)

1. MSD Manual Professional: Brugada Syndrome
2. StatPearls: Brugada Syndrome

Cross-references