Friday, December 26, 2014

Brugada syndrome: the latest

Here's a new review.

From the article:

Originally, three repolarization patterns were described: a) Type-1 ECG pattern, in which a coved ST-segment elevation greater than or equal to 2 mm is followed by a negative T-wave, with little or no isoelectric separation, with this feature being present in greater then 1 right precordial lead (from V1 to V3); b) Type-2 ECG pattern, also characterized by a ST-segment elevation but followed by a positive or biphasic T-wave that results in a saddle-back configuration; c) Type-3 ECG pattern, a right precordial ST-segment elevation less than or equal to 1 mm either with a coved-type or a saddle-back far, only the ECG type 1 pattern is the sine qua non BrS diagnosis: J-point elevation of greater than 2 mm with a coved (downward convex) ST segment (Figure 1).9 Both type 2 and 3 are not considered diagnostic. The ECG type 1 pattern may be spontaneously evident or induced by a provocative drug challenge test using intravenous Class 1A or 1C antiarrhythmic drugs.

Concerning the genetics:

Brugada syndrome is a disease with an autosomal dominant pattern of transmission. Incomplete penetrance is frequent in families, and the disease can be sporadic in up to 60% of patients.17 In 1998, the first pathogenic mutation in the SCN5A gene was identified.18 This gene encodes the alpha subunit of the cardiac sodium channel (Nav1.5). Since then, more than 350 pathogenic mutations in several genes have been published (SCN5A, GPD1L, SCN1B, SCN2B, SCN3B, RANGRF, SLMAP, KCNE3, KCNJ8, HCN4, KCNE5, KCND3, CACNA1C, CACNB2B, CACNA2D1, and TRPM4) (Table 1).19 These genes encode subunits of cardiac sodium, potassium, and calcium channels as well as genes involved in the trafficking or regulation of these channels. Despite the high number of gene mutations, only about 35% of BrS patients have been determined to have a genetic cause. Of them, nearly 30% carry a pathogenic mutation in the SCN5A gene.20 All other genes together are responsible for about 5% of all BrS cases. Therefore, 65% of cases do not have a genetic origin.

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