Abstract: AIM To detect the relationship between left or right atrial serum tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) levels in atrial fibrillation patients with non- structural heart disease and to explore inflammatory changes in different types of atrial fibrillation and possible clinical implications. METHODS 59 patients were selected intending to have radiofrequency ablation of arrhythmias, who had no structural heart disease. 42 patients had atrial fibrillation, 17 patients had paroxysmal supraventricular tachycardia or pre-bowel syndrome. Samples were collected from left and right atrial blood before surgery and tested for serum TNF-α, IL-6 levels by ELISA, echocardiography to measure left atrial diameter. Statistical methods compared differences of the two groups. RESULTS In comparison with the control group of atrial fibrillation, the atrial fibrillation group significantly increased left atrial diameter (36±7) mm compared with the control group (31±4) mm (P <0.01); AF group left and right atrium TNF-α levels were significantly higher (P<0.01); AF group left and right atrium serum IL-6L was significantly higher (P<0.05); persistent AF group, the serum IL-6 (17±9) pg/ml was higher than the paroxysmal AF group (12±5) pg/ml (P<0.05). The serum TNF-α levels and persistent atrial fibrillation and paroxysmal atrial fibrillation had no significant differences. CONCLUSION The serum TNF-α, IL-6 levels have relationsips to development of atrial fibrillation with non-structural heart disease and there was an increasing trend of serum IL-6 levels in patients with persistent atrial fibrillation when compared with the paroxysmal patients, and IL-6 could potentially be a factor in predicting sustained atrial fibrillation.