title: A genotype-dependent intermediate ECG phenotype in patients with persistent lone atrial fibrillation genotype ECG-phenotype correlation in atrial fibrillation.
abstract: BACKGROUND
  Atrial fibrillation (AF) is heterogeneous at the clinical and molecular levels. Association studies have reported that common single-nucleotide polymorphisms in KCNE1 and SCN5A may predispose to AF. In this study, we tested the hypothesis that specific AF-associated genotypes confer variation on the appearance of AF assessed by analysis of fibrillatory rate of the atria.
  
  
  RESULTS
  Twenty-six nonrelated patients (21 males, mean age 55+/-12 years) with persistent lone AF (median AF duration 5 weeks) not taking class I or III antiarrhythmic drugs were studied. Fibrillatory rate was obtained by spatiotemporal QRST cancellation and time-frequency analysis of the index surface ECG. Genotypes at the AF-associated loci in KCNE1 (S38G) and SCN5A (H558R) were determined by direct DNA sequencing. The atrial fibrillatory rate was 418+/-50 fibrillations per minute (range, 336 to 521) in the study cohort. Carriers of the 38GG KCNE1 genotype (n=13) had significantly lower fibrillatory rates (392+/-36 versus 443+/-49 fibrillations per minute, P0.006) compared to those with GS or SS genotype (n=13). Six patients (23%) with fibrillatory rates >450 fibrillations per minute, all had either the GS or SS genotype (Chi2 P0.008). In contrast, both the heterozygeous and homozygeous SCN5A H558R polymorphism had no effect on fibrillatory rate. There were no significant associations between fibrillatory rate and clinical (age, gender, AF duration, drug treatment) or echocardiographic (left atrial diameter, left ventricular ejection fraction) variables. In multivariable regression analysis, the KCNE1 S38G genotype (SS/GS coded 0, GG coded 1) was the only independent predictor of fibrillatory rate (beta = -0.437, P = 0.006) with a SE of the estimate of 44 fibrillations per minute.
  
  
  CONCLUSIONS
  This study suggests that atrial fibrillatory rate obtained from the surface ECG is at least in part determined by KCNE1 (S38G) genotype, implying that this variant exerts functional effects on atrial electrophysiology. This intermediate ECG phenotype may be useful for elaborating genetic influences on AF mechanisms and identifying subsets of patients for variability in AF susceptibility or response to therapies.
authors.affiliation: Department of Electrophysiology, Heart Center, Leipzig University, Germany. dani11@gmx.net
authors.forename: Daniela
authors.initials: D
authors.lastname: Husser
authors.forename: Martin
authors.initials: M
authors.lastname: Stridh
authors.forename: Leif
authors.initials: L
authors.lastname: Sörnmo
authors.forename: Dan M
authors.initials: DM
authors.lastname: Roden
authors.forename: Dawood
authors.initials: D
authors.lastname: Darbar
authors.forename: Andreas
authors.initials: A
authors.lastname: Bollmann
mesh_terms: D000328:Adult; D000368:Aged; D001281:Atrial Fibrillation / Q000235:genetics* / Q000503:physiopathology; D004562:Electrocardiography; D005260:Female; D005787:Gene Frequency; D020022:Genetic Predisposition to Disease; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009124:Muscle Proteins / Q000235:genetics*; D062554:NAV1.5 Voltage-Gated Sodium Channel; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide; D024642:Potassium Channels, Voltage-Gated / Q000235:genetics*; D011446:Prospective Studies; D012042:Registries; D012044:Regression Analysis; D018570:Risk Assessment; D012307:Risk Factors; D015222:Sodium Channels / Q000235:genetics*
chemical_list: C489622:KCNE1 protein, human; D009124:Muscle Proteins; D062554:NAV1.5 Voltage-Gated Sodium Channel; D024642:Potassium Channels, Voltage-Gated; C568320:SCN5A protein, human; D015222:Sodium Channels