ObjectiveTo study on the relationship of serum apelin level with inflammation in patients with atrial fibrillation (AF). MethodsWe recruited 58 patients with valvular heart disease who admitted in our hospital between October 2014 and December 2014 and planned to undergo surgery, including 29 patients with persistent AF (an AF group) and 29 patients with sinus rhythm (a SR group). There were 14 males and 15 females in the AF group at an average age of 57±8 years. There were 20 males and 9 females in the SR group at an average age of 54±10 years. The left atrial diameter (LAD) and ejection fraction (EF) were detected by echocardiography. The levels of serum apelin and interleukin-6 (IL-6) were measured by enzyme linked immuno sorbent assay, and the level of high-sensitivity C-reactive protein (hs-CRP) were determined by turbidimetric inhibition immuno assay. ResultsCompare with the SR group, the serum apelin level (201.94±71.96 pg/ml vs. 286.72±129.33 pg/ml) and EF (54.52%±3.94% vs. 56.41%±2.85%) were significantly lower in the AF group, while the hs-CRP (5.58±12.90 mg/L vs. 1.89±3.55 mg/L), IL-6 (2.59±0.64 pg/ml vs. 2.26±0.55 pg/ml) and LAD (57.10±11.69 mm vs. 43.07±5.31 mm) were significantly higher in the AF group (P<0.05). Correlation analysis showed that the apelin level was negatively correlated with hs-CRP and LAD (r=-0.308, P=0.019; r=-0.313, P=0.017), and were positively correlated with EF (r=0.265, P=0.044). ConclusionSerum apelin level is significantly lower in patients with AF and levels of inflammation makers are significantly higher. Apelin may be closely related to AF and inflammation, and may take part in the occurrence and maintenance of AF through the regulation of inflammatory processes.