Are epicardial adipose tissue and transforming growth factor beta1 risk factors of atrial fibrillation in patients with metabolic syndrome?

Objective. To determine the relationship between the thickness of epicardial adipose tissue (EAT) and the serum concentration of transforming growth factor beta1 (TGF-beta1) with the severity of left atrial myocardial fibrosis in patients with metabolic syndrome (MS) and to define the role of these factors in atrial fibrillation (AF) development. Design and methods. The study included 258 patients: patients with MS without AF (n = 57), patients with MS and AF (n = 83), patients with AF without MS (n = 36), and otherwise healthy subjects without cardiovascular disease and metabolic disorders (n = 82). Serum level of TGF-beta1 was assessed by ELISA. Epicardial adipose tissue thickness (EAT) was measured by ultrasound on the Vivid 7 apparatus (General Electric, USA). To assess fibrosis we constructed anatomical and amplitude maps of the left atrium (LA) using the non-fluoroscopic electro-anatomical mapping system CARTO3 (Biosense Webster, USA) Results. EAT in patients with MS and AF is higher than in patients with MS without AF (4,7 ± 1,9 and 4,2 ± 1,6 mm, respectively, p = 0,023), higher than in patients with AF without MS (4,7 ± 1,9 and 4,3 ± 1,7 mm, p = 0,01) and significantly higher than in healthy subjects (4,7 ± 1,9 and 2,3 ± 0,9 mm, respectively, p < 0,001). The EAT positively correlated with the percentage of fibrosis of LA estimated by the mapping method (r = 0,549, p < 0,0001). The serum concentration of TGF-beta1 in patients with AF and MS was 6700,2 [2588,4, 17500,3] pg/ml. It was 4,7 times higher than in healthy subjects (p < 0,0001), 2,6 times higher than in patients with MS without AF and higher than in patients with AF without MS. Positive correlations were found between TGF-beta1 and LA volume (r = 0,203, p = 0,03). Binomial regression analysis showed that the probability of AF presence in patients with MS was higher when traditional predictors of this arrhythmia were present — the volume of the LA (odds ratio (OR) = 1,092, 95% confidence interval (CI) 1,026–1,162, p = 0,005), systolic blood pressure (OR = 1,093, 95% CI 1,021–1,169, p = 0,01), as well as EAT (OR = 2,21, 95% CI 1,111–4,386, p = 0,024) and TGF-beta1 (OR = 1,01, 95% CI 1,006–1,015, p = 0,002). Conclusions.Thickness of epicardial adipose tissue and transforming growth factor beta1 are associated with AF also in MS. Probably, epicardial fat and transforming growth factor beta1 stimulate atrial myocardial fibrosis which is the risk factor of AF.