 The purpose of this study is 1 to characterize T-cell response in patients with atrial fibrillation, and 2 to analyze the changes of T-cell response after radio-frequency catheter ablation of atrial fibrillation. First, immune-phenotyping and cytokine profiling of T cells from patients with atrial fibrillation will performed. Next the difference of T-cell immunity among various type of atrial fibrillation patients will be analyzed. Finally the changes of T-cell response and cytokines after radio-frequency catheter ablation of atrial fibrillation will be assessed. 