Abstract: Objective To investigate the correlation of serum interleukin-6 (IL-6) and C-reactive protien (CRP) lev⁃ els with left atrial thrombus and severe spontaneous echocontrast (SEC) in patients with atrial fibrillation (AF). Methods A case-control study of patients with atrial fibrillation (n=76) was carried out. All patients were divided into control group (n= 45) and study group (n=31) according to their conventional echocardiography performance. Serum IL-6 and CRP were exam⁃ ined in both groups. Results The levels of serum IL-6 in patients with thrombus and severe SEC were (324.13±42.86) ng/L and (332.29±53.17) ng/L, respectivly which is higher than that in patient without thrombus or without severe SEC (108.75± 25.43) ng/L and (93.59±27.82) ng/L respectively. In parallel, CRP levels in patients of thrombus and severe SEC were (66.97±17.65) mg/L and (71.81±20.19) mg/L respectively which is higher than that in patients without thrombus or without severe SEC (17.28±6.52) mg/L and (16.76±8.73) mg/L respectively. All differences were of statistically significant(P＜0.05). Conclusion Increase of serum IL-6 and CRP as well as high systemic inflammatory state correlate with left atrial thombus and severe SEC in patients with AF.

Key words: interleukin-6, C-reactive protien, atrial fibrillation, left atrial thombus