Efficacy and safety of dextrose-insulin in unmasking non-diagnostic Brugada ECG patterns

Arrhythmias induced by dextrose-insulin challenge test in nondiagnostic Brugada ECG patterns

INTRODUCTION

Dynamic ECG changes in Brugada syndrome (BrS) are influenced by several factors, may not be apparent, and can be unmasked by a drug test.

METHODS AND RESULTS

Four of six patients with nondiagnostic Brugada ECG index patterns underwent a dextrose-insulin challenge test that resulted in J-ST segment elevation and triggered arrhythmias.

CONCLUSION

Insulin action may be due in part to an outward shift in the K+ current at the end of action potential phase 1 and the dispersion of repolarization, leading to local re-entry with arrhythmogenicity. This effect is likely a phenomenon-specific to BrS.

Genotype/Phenotype Relationship in a Consanguineal Family With Brugada Syndrome Harboring the R1632C Missense Variant in the SCN5A Gene

Brugada syndrome (BrS) is a known cause of sudden cardiac death. The genetic basis of BrS is not well understood, and no one single gene is linked to even a majority of BrS cases. However, mutations in the gene SCN5A are the most common, although the high amount of phenotypic variability prevents a clear correlation between genotype and phenotype. Research techniques are limited, as most BrS cases still remain without a genetic diagnosis, thus impairing the implementation of experimental models representative of a general pathogenetic mechanism. In the present study, we report the largest family to-date with the segregation of the heterozygous variant NM_198056:c.4894C>T (p.Arg1632Cys) in the SCN5A gene. The genotype-phenotype relationship observed suggests a likely pathogenic effect of this variant. Functional studies to better understand the molecular effects of this variant are warranted.