After a 24 hour treatment, significant decreases were observed in the expression of VEGF (p = 0.0286), TNF-α (p = 0.0286) and IL-1β (p = 0.0286) and a trend of decreased expression in CCL2/MCP-1 (p = 0.057) in mast cells treated with healthy AF DCCM compared to untreated basal controls and degenerate AF DCCM, suggesting an inhibitory role for AF cells on mast cell phenotype (Fig. 5). This evidence concerns the gene IL1B and atrial fibrillation.