CardiologyTier 2Disease (DEADMAN)

Advanced arrhythmias and channelopathies - Brugada syndrome

Description

Sodium channelopathy in a structurally normal heart
Coved ST elevation in the right precordial leads + risk of polymorphic VT/VF
Diagnosis requires a type 1 pattern:
- Coved ST elevation >=2 mm with a descending negative T wave
- In >=1 of V1-V2, including in high (2nd-3rd ICS) lead positions
- Older criteria required two leads; current criteria accept one, in standard or high positions
Type 2 and 3 (saddleback) patterns are not diagnostic - they need provocation

M>F ~8-10:1 despite autosomal dominant inheritance
Highest prevalence in South-East Asia - the "sudden unexplained nocturnal death syndrome" phenotype
Presents in the 3rd-4th decade
Events occur at rest, during sleep, or with fever - not on exertion

SCN5A loss-of-function - the commonest identified gene, found in only ~20-30%
- The same gene causes LQT3 through gain of function
Mechanism
- dec inward sodium current (INa)
- -> heterogeneous RVOT epicardial repolarisation
- -> phase 2 reentry
- -> polymorphic VT / VF
Modulators that unmask or provoke:
- Fever
- High vagal tone, sleep, large meals, alcohol
- Sodium channel blocking drugs, cocaine

Type 1 pattern plus at least one of

Provocation testing

IV ajmaline, flecainide or procainamide to unmask the pattern
Indicated for a suspicious ECG with syncope, or a family history of Brugada or unexplained SCD
Only with full resuscitation facilities available

Exclude phenocopies

Every patient

*Treat fever immediately with paracetamol* - the single most important instruction
Avoid sodium channel blocking drugs - flecainide, tricyclics, lithium, some anaesthetic agents
- Give the patient the drug-avoidance list, not just the advice
Avoid excess alcohol and large meals
Family screening - ECG +/- cascade genetic testing

ICD

The only therapy proven to prevent sudden death
Indicated for:
- Aborted sudden death or documented sustained VT/VF, OR
- Spontaneous type 1 pattern with unexplained syncope
Asymptomatic patients with only a drug-induced type 1 pattern generally do not need one
Subcutaneous ICD often suitable - no pacing requirement

Recurrent VT/VF

Risk is concentrated in those with a spontaneous type 1 pattern plus syncope or prior arrest
Asymptomatic patients with only a drug-induced pattern have a low event rate
Events cluster at rest, at night, and during febrile illness

Monitor

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