Objectives A variety of studies have evaluated whether increased CRP levels have association with AF recurrence after catheter ablation. However, the results remain inconsistent. So this meta-analysis was conducted to offer suggestion.

Methods Electronic databases were searched until 31st December 2012 for any CRP association studies, including PubMed, Embase, Medline, ISI Web of Knowledge and ScienceDirect. Overall and subgroup analyses were performed. Standardised mean difference (SMD) and 95% confidence interval (CI) were used to evaluate the associations between CRP levels and post-ablation AF recurrence. Statistical analysis was performed with Review Manager 5.2 and STATA11.0.

Results Seven available studies were identified, which included 526 patients (179 recurrence versus 347 no recurrence). Overall, increased baseline CRP levels have significant positive association with post-ablation AF recurrence. The SMD in the CRP levels was 0.65 units (95% confidence interval 0.30 to 0.99), and the z-score for overall effect was 3.70 (p = 0.0002). The heterogeneity test showed that there were moderate differences between individual studies (p = 0.006; I² = 67%). Meta-regression revealed that different sample sizes of studies possibly accounted for the heterogeneity. Positive associations were also found in subgroup analyses based on sample size. When stratifying for ethnicity, similarly significant associations were found in both European (Caucasian) and Asian.

Conclusions Inflammation of AF involved in electrophysiological and structural atrial remodelling and facilitated the disease development and perpetuation. Atrial specimens obtained by endomyocardial biopsy showed clusters of lymphomononuclear cells compatible with diagnosis of myocarditis in 66% of patients with lone AF, as well as, activated T lymphocytes were found in left atrial endocardium, supporting the role of local inflammation as a potential trigger of AF. CRP, an acute-phase protein produced in the liver, is a sensitive biomarker of systemic inflammation in several cardiovascular diseases. Elevated CRP levels are associated with increased risk of cardiovascular events. In the study from Narducci ML et al., atrial tissue CRP was significantly more frequent in patients with paroxysmal AF than persistent AF and there was a trend for the association between atrial tissue CRP and late recurrence of AF. The higher proportion of atrial CRP-positive specimens in paroxysmal AF than in persistent AF group may be an initial feature of myocardial damage via activation of the complement system, opsonisation, chemotaxis, and activation of inflammatory cells by this acute phase protein. Furthermore, a rise in CRP was related to left atrial size and dysfunction offered support the association between inflammation and structural remodelling.