Interleukin-6 and atrial fibrillation in patients with coronary artery disease: Data from the Heart and Soul Study

Background Previous studies suggest that markers of inflammation are elevated in patients with atrial fibrillation (AF). However, because inflammation has been implicated in contributing to risk of both AF and coronary artery disease (CAD), which are often present in the same populations, it is important to control for confounding by the presence of CAD. We therefore examined several biomarkers of inflammation and ultimately genotyped IL-6 polymorphisms in patients with AF in a cohort of subjects with known CAD. Methods We performed a cross-sectional analysis of 971 participants in the Heart and Soul Study, 46 of whom had AF. Interleukin-6, C-reactive protein, tumor necrosis factor-a, CD-40 ligand, monocyte chemoattractant protein-1, and fibrinogen levels were measured. Results In both unadjusted and adjusted analyses, IL-6 was the only biomarker significantly associated with AF (median IL-6 3.76 and 2.52 pg/mL in those with and without AF, respectively, P =.0005; adjusted odds ratio 1.77, P =.032). The IL-6-174CC genotype was significantly associated with the presence of AF in the adjusted analysis (odds ratio 2.34, P =.04) and with higher IL-6 levels (P =.002). Conclusions In this cohort of subjects with CAD, AF was significantly associated with elevated IL-6 levels and the IL-6-174CC genotype. No associations were found with other biomarkers, including C-reactive protein. This suggests that IL-6 is a uniquely important mediator in the pathophysiology of AF.