Genotype-phenotype relationship in Brugada syndrome: electrocardiographic features differentiate SCN5A-related patients from non-SCN5A-related patients.
OBJECTIVE
We have tested whether a genotype-phenotype relationship exists in Brugada syndrome (BS) by trying to distinguish BS patients with (carriers) and those without (non-carriers) a mutation in the gene encoding the cardiac sodium channel (SCN5A) using clinical parameters.


BACKGROUND
Brugada syndrome is an inherited cardiac disease characterized by a varying degree of ST-segment elevation in the right precordial leads and (non)specific conduction disorders. In a minority of patients, SCN5A mutations can be found. Genetic heterogeneity has been demonstrated, but other causally related genes await identification. If a genotype-phenotype relationship exists, this might facilitate screening.


METHODS
In a multi-center study, we have collected data on demographics, clinical history, family history, electrocardiogram (ECG) parameters, His to ventricle interval (HV), and ECG parameters after pharmacologic challenge with I(Na) blocking drugs for BS patients with (n = 23), or those without (n = 54), an identified SCN5A mutation.


RESULTS
No differences were found in demographics, clinical history, or family history. Carriers had a significantly longer PQ interval on the baseline ECG and a significantly longer HV time. A PQ interval of > or =210 ms and an HV interval > or =60 ms seem to be predictive for the presence of an SCN5A mutation. After I(Na) blocking drugs, carriers had significantly longer PQ and QRS intervals and more increase in QRS duration.


CONCLUSIONS
We observed significantly longer conduction intervals on baseline ECG in patients with established SCN5A mutations (PQ and HV interval and, upon class I drugs, more QRS increase). These results concur with the observed loss of function of mutated BS-related sodium channels. Brugada syndrome patients with, and those without, an SCN5A mutation can be differentiated by phenotypical differences.
Smits
Jeroen P P
JP
Experimental and Molecular Cardiology Group, Academic Medical Center, University of Amsterdam, 1100 DE Amsterdam, The Netherlands.
Eckardt
Lars
L
Probst
Vincent
V
Bezzina
Connie R
CR
Schott
Jean Jacques
JJ
Remme
Carol Ann
CA
Haverkamp
Wilhelm
W
Breithardt
Günter
G
Escande
Denis
D
Schulze-Bahr
Eric
E
LeMarec
Hervé
H
Wilde
Arthur A M
AA
D000328:Adult; D000889:Anti-Arrhythmia Agents; D002037:Bundle-Branch Block / Q000175:diagnosis / Q000235:genetics* / Q000503:physiopathology*; D004252:DNA Mutational Analysis; D004562:Electrocardiography; D005260:Female; D005838:Genotype; D006579:Heterozygote; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D062554:NAV1.5 Voltage-Gated Sodium Channel; D010641:Phenotype; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D015222:Sodium Channels / Q000235:genetics*; D013577:Syndrome
D000889:Anti-Arrhythmia Agents; D062554:NAV1.5 Voltage-Gated Sodium Channel; C568320:SCN5A protein, human; D015222:Sodium Channels