C-Reactive Protein and The Risk of Atrial Fibrillation: A Systematic Review and Meta-Analysis.

There is increasing evidence linking C-reactive protein (CRP) and atrial fibrillation (AF). Despite the abundance of literature, confusion exists regarding this association because of inconsistent results. MEDLINE and Cochrane Controlled Trials Register databases were carefully searched through July, 2009 combining the following terms "C-reactive protein" and "atrial fibrillation". Reference lists of selected articles and reviews were also screened to identify additional relevant studies. Of the 129 studies initially identified, 8 studies with 7507 subjects (719 with AF) were included in the meta-analysis. Analysis yielded a relative risk of 1.63 (1.43, 1.86) for occurrence of AF when CRP level was above a cut off of 3-3.5 mg/l. When 3 studies with data on a higher cut off of 4.5-5.0 mg/l were analyzed separately, the relative risk was 4.03 (3.1, 5.25). Our study suggests that elevated CRP is associated with increased risk for AF. The risk appears incremental with higher CRP levels conferring proportionately increased risk. There is an urgent need for further large scale, well designed prospective studies to assess the relationship between CRP and AF.