CXCL8 and atrial fibrillation: Several studies have demonstrated increased levels of inflammatory biomarkers (e.g., interleukin-2 [IL-2], IL-6, and IL-8, tumor necrosis factor-α, and C-reactive protein) in patients with AF (Engelmann and Svendsen, 2005; Liu et al., 2007; Guo et al., 2012).