TNF and atrial fibrillation: Indeed, clinical studies have indicated that the recruitment of immune cells such as monocytes and macrophages and the levels of pro‐inflammatory cytokines, such as C‐reactive protein (CRP), tumour necrosis factor (TNF)‐α, interleukin (IL)‐2, IL‐6, IL‐8 and monocyte chemoattractant protein (MCP)‐1, are significantly increased in the atria of patients with AF.2, 3, 4