Makindo Medical Notes.com

Related Subjects: |Brugada Syndrome |Long QT syndrome (LQTS) Acquired |Long QT syndrome (LQTS) Congenital |Torsades de Pointes |Ventricular Fibrillation |Ventricular Tachycardia |Resuscitation - Adult Tachycardia Algorithm |Automatic Implantable Cardioverter Defibrillator (AICD)

The only known effective treatment is an implantable defibrillator

About

• Brugada syndrome is a channelopathy causing sudden cardiac death with distinctive ECG changes
• Affects 1-6 per 1000 especially SE Asian Men. Men x 8 incidence
• Brugada was discovered in 1992 by two Spanish brothers – cardiologists Pedro and Josep Brugada.
• The genetic work was done by their brother Ramon.

Genetics

• Most commonly implicated gene is SCN5A, which encodes a sodium channel in the heart (NaV1.5).
• Other genes, CACNA1C, CACNB2, and SCN10A, also associated with Brugada syndrome but less common.

Aetiology

• There is a reduction in the inward sodium current during phase 0 of the cardiac action potential
• This creates an imbalance in the ion currents during the repolarization phase
• Appears to affect particularly the right ventricular outflow
• Up to 30% have loss of function mutations in the sodium channel SCN5A gene (Chr 3).

Types

• Type 1: classical "coved-type" ST-segment elevation > 2 mm in the RV leads (V1-V3), followed by a negative T wave.
• Type 2/3: "saddleback" ST-segment elevation but less specific and needs further tests for confirmation.

Clinical

• Sudden Unexplained Nocturnal Death Syndrome
• Syncope and cardiac arrest

Investigations

• FBC, U&E etc all normal
• Structure: The heart is at least macroscopically structurally normal and so CXR, Echo, Cardiac MRI, catheterization, and myocardial biopsy findings are normal
• Prolonged telemetry/ 24 hr tape or longer may show VT/TDP
• ECG shows ST segment elevation in leads V1 to V3. The QT interval is usually normal. Incomplete or complete right bundle branch block. Polymorphic ventricular tachycardia and VF. Challenge with sodium channel blockers is positive when the drug generates a J wave with an absolute amplitude of 2 mm or more in leads V1, V2, and/or V3 with or without an RBBB.
• Genetically testing for a mutation in SCN5A
• Provocation Testing: If ECH pattern is not present at baseline, it may be unmasked by administering a sodium channel blocker, such as ajmaline, flecainide, or procainamide, under controlled conditions. This test should only be done in a clinical setting with appropriate resuscitation equipment available.

ECG/EKG

Risk factors for SCD include

• Aborted SCD
• ventricular arrhythmias
• Spontaneous ST elevation
• Inducible VT/VF
• Syncope

Management

• Avoid High fevers, excess alcohol, large meals, Cocaine, Alpha blockers, TCAs, First generation antihistamines, Flecainide, propafenone, procainamide, disopyramide
• Avoid harmful drugs - see Safe drugs in Brugada website
• Idiopathic VF - sudden death is the main concern. No drug treatment for Brugada syndrome is recommended. ICD is the treatment of choice for those with an inducible arrhythmia on EPS. ICD may be considered in high-risk asymptomatic family members but is controversial
• Quinidine has been useful for some. Catheter ablation of the RVOT has been considered for some with recurrent shocks

References

• Safe drugs in Brugada website
• Arrhythmia Essentials