Channelopathies
- Brugada
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- Complex abnormalities of sodium channel
- Common in Laos and Japan, often presents in 20-30s
- AD inherited, variable penetrance
- Symptoms
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- Syncope – can even occur at night. Syncope during fever should also raise suspicion (treat fevers with paracetamol quickly)
- But… faints are common. Important to correlate rhythm with symptoms
- Small risk of SCD (may be family hx of this)
- Mean age of those who do arrest is 41
- The arrythmia is VF (so arrhythmogenic syncope is v rare as this would be self-terminating VF), however syncope still represents a high-risk feature in Brugada
- Also higher risk of AF which could be to blame
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- ECG
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- Elevated J point in V1/V2, downsloping ST segment which is coved
- Do a modified ECG – high RV leads. Usually V1 and V2 are in the 4th ICS. Move leads V1-V3 up 1 or 2 intercostal spaces (eg V1 and V2 in the 2nd and 3rd ICS instead). Can transform a type 3 Brugada into a type 1 Brugada
- Might not be present in all ECGs – so check all ECGs!
- Hard to see classic pattern if tachycardic
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- Mimics include pectus exacavatum, athletes’ heart, incomplete RBBB, high take off
- Diagnosis and management
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- Flecanide challenge can help diagnose
- Do genetic testing for the gene, and family might need testing
- Can do the Shanghai risk score
- Needs ICD if high risk, not drugs.
- Check brugadadrugs.org to know what’s contraindicated
- Ensure – electrolyte balance, avoid ETOH, treat fevers promptly and avoid strenuous exercise
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- Long QT syndrome (can cause polymorphic VT)
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- QTC >460, but risk of arrhythmia begins to rise properly >500
- AD inheritance, 1:2500
- Consider other causes of long QT eg drugs or IHD
- Risk of SCD 0.9%/year, but 5%/year if syncopal
- Better classified by genotype than phenotype
- Can do the modified Schwartz score to help diagnose
- Type 1 – 35%
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- Broad based T wave
- Arrythmias (esp VT / torsades) triggered by exercise esp swimming
- Often presents in kids, esp boys)
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- Type 2 – 30%
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- Bifed T wave which extends QT interval
- Tends to present in puberty, esp girls. Arrythmias can be triggered by morning alarm clock
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- Type 3 – 10%
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- Long ST segment, late peaking T wave
- Presents in puberty, esp girls
- Arrythmias, esp at lower heart rates
- Penetrance varies by type (1 – 65%, 2 – 80%, 3 – 90%)
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- Management
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- Give betablocker
- Left stellectomy for types 1 and 2
- K+ supplements for type 2
- Sodium channel blockers and PPM for type 3
- Avoid certain meds (check crediblemeds.org)
- Left cardiac sympathetic denervation and mexiletine also options.
- Treat electrolyte abnormalities quickly.
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- Short QT – rare, AD inheritance
- Catecholaminergic polymorphic VT
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- Disorder of calcium handling
- Recurrent syncope since childhood, esp in adrenaline heavy scenarios (due to non-sustained VT) or when given adrenaline
- Treat with betablockers
- Consider ICD insertion (can be a difficult decicion)
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- Early repolarisation syndrome (see ECG essentials)
- Progressive cardiac conduction defect (PCCD)
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- Rare, often inherited AD
- Risk of complete heart block, SCD
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