Brugada syndrome

Introduction

1st described in 1986 by Brugada in Barcelona, but 1st abstract of 4 patients in 1992 and 1st paper of 8 patients in 1992 by Pedro and Josep Brugada
SCN5A gene mutation identified in 1998 and since then over 200 mutations of this gene have been identified but loss of function of sodium channel only identified in 18-30% of cases
ECG: J point elevated > 2mm with complete or incomplete Right Bundle Branch Block (RBBB) and ST elevation in V1-2 with RSR' pattern in young people
rare but important, often present as tachycardia or near syncope
it is an example of a channelopathy - a disease caused by an alteration in the transmembrane ion currents that together constitute the cardiac action potential.
in 10-30% of cases, mutations in the SCN5A gene, which encodes the cardiac voltage-gated sodium channel Nav 1.5, have been found¹⁾
27% will develop VT (often torsade de pointes VT) or ventricular fibrillation (VF) resulting in sudden cardiac death within 2-3 years without an implantable cardioverter-defibrillator being placed.
- risk of cardiac events within 5yrs of diagnosis for males is ~12% whilst for females is only ~3%

Brugada syndrome is a diagnosis of EXCLUSION!
- ECG may be normal and only become abnormal in certain conditions such as fevers
- many conditions mimic Brugada syndrome ECG pattern:
- type 2 and 3 Brugada patterns are NOT diagnostic
- type 1 pattern may be unmasked by superior placement of R precordial leads or by challenge with class I sodium channel blockers

genetically determined and has an autosomal dominant pattern of transmission in about 50% of familial cases.
SE Asia has a rate 9x that of Caucasians with 3.7 per 1000 having it with a gender ratio of 9:1 males:females
- type 1 ECG pattern has prevalence of 0.15-0.27% in those from SE Asia
almost absent in north African ethnicities

all have raised J wave > 2mm but only type 1 is reliably diagnostic (albeit once other conditions that cause this are excluded)

feature	type 1	type 2	type 3
T wave	negative	positive or biphasic	positive
ST elevation	coved	saddleback	saddleback
ST terminal portion	gradually descending	elevated > 1mm	elevated < 1mm

ECG changes may be suppressed in exercise testing
QRS duration may be a marker for mortality
ECG pattern (J wave elevation in V1-3) may be unmasked²⁾ by sodium blockers such as:
- flecainide 2 mg/kg (maximum 150 mg) over 10 minutes BUT this should only be performed in monitored, resuscitation environments, and only for type 2 or 3 cases as it does not add to diagnosis work up of type 1 cases
- isoprenaline and sodium lactate may be effective as antidotes if the sodium channel blocker induces an arrhythmia.

early repolarisation syndrome
- most marked in V4 with notching at J point; tall upright T waves; reciprocal ST depression in aVR. not in aVL when limb leads involved
other normal variants especially in men
- “normal young male pattern ST elevation” - 90% healthy young men; most marked V2 1-3mm concave elevation'
- “ST elevation of normal variant” - V3-5 with inverted T waves, short QT, high QRS voltage

¹⁾

²⁾