Source of inflammatory markers in patients with atrial fibrillation

Elevated levels of C-reactive protein and other inflammatory markers have been reported in some patients with atrial fibrillation (AF). Whether this finding is related to AF per se or to other conditions remains unclear. In addition, the source of inflammatory markers is unknown. Therefore, in the present study, we sought to assess the extent and the source of inflammation in patients with AF and no other concomitant heart or inflammatory conditions. The study group consisted of 29 patients referred for radiofrequency catheter ablation: 10 patients with paroxysmal AF, 8 patients with permanent AF, and 10 control patients with Wolf-Parkinson-White (WPW) syndrome and no evidence of AF (mean age 54 +/- 11 vs. 57 +/- 13 vs. 43 +/- 16). No patient had structural heart diseases or inflammatory conditions. High-sensitive C-reactive protein, interleukin-6 (IL-6), and interleukin-8 (IL-8) were assessed in blood samples from the femoral vein, right atrium, coronary sinus, and the left and right upper pulmonary veins. All samples were collected before ablation. Compared with controls and patients with paroxysmal AF, patients with permanent AF had higher plasma levels of IL-8 in the samples from the femoral vein, right atrium, and coronary sinus, but not in the samples from the pulmonary veins (median values in the femoral vein: 2.58 vs. 2.97 vs. 4.66 pg/mL, P = 0.003; right atrium: 2.30 vs. 3.06 vs. 3.93 pg/mL, P = 0.013; coronary sinus: 2.85 vs. 3.15 vs. 4.07, P = 0.016). A high-degree correlation existed between the IL-8 levels in these samples (correlation coefficient between 0.929 and 0.976, P < 0.05). No differences in the C-reactive protein and IL-6 levels were noted between the three groups of patients. The normal levels of C-reactive protein and IL-6, along with the elevated levels of IL-8 in patients with permanent AF but not in those with paroxysmal AF, suggest a link between a low-grade inflammatory reaction and long-lasting AF. The elevated IL-8 levels in the peripheral blood, right atrium, and coronary sinus but not in the pulmonary veins suggest a possible source of inflammation in the systemic circulation.