ABC | Volume 114, Nº4, April 2020

Original Article Correia et al. CA lesions and AF recurrence - a meta-analysis Arq Bras Cardiol. 2020; 114(4):627-635 Figure 1 – Study selection flow diagram. 790 records identified database search: 695 in PubMed 95 in Cochrane Central Register of Controlled Trials 762 records screened 762 records after duplicates removed 20 full-text articles assessed for eligibility 8 studies included in the qualitative analysis 4 studies included in the meta-analysis 720 records excluded because they were unrelated to this meta-analysis or were review articles 12 studies excluded: Because were unrelated to this systematic review and meta-analysis 4 studies excluded in the meta-analysis because they did not report mean and standard deviation of the volume of the left atrial scars identified, p = 0.560). The study also performed binary logistic regression, which confirmed that there was no significant association between identification of ablation lesions and freedom from AF. 16 The 2015 study by Akoumet al. 14 found that ablation‑induced scarring was not a statistically significant predictor of less AF recurrence (hazard ratio=0.95; p=0.097). However, according to this same study, when performing scar homogenization, inducing ablation lesions in prior fibrotic tissue leads to a lower recurrence rate, because less heterogeneous fibrotic tissue remains. 14 Meta-analysis The present meta-analysis shows that total LA scarring post-ablation is associated with less AF recurrence after CA (SMD = 0.52, 95% CI 0.27 – 0.76, p < 0.0001), as shown in Figure 2. The heterogeneity test showed that there were no significant differences between studies (p = 0.4, I² = 0%). A funnel plot (Figure 3) was used to verify the existence of publication bias. There was no obvious asymmetry, suggesting that there was no publication bias. Discussion The importance of CA for AF correction has grown since its introduction. A recent meta-analysis by Kheiri et al. that included seven randomized controlled trials showed that CAwas associated with better outcomes in patients with AF and heart failure, in comparison with medical treatment. 17 Therefore, interventional cardiologists should seek ablation strategies that reduce AF recurrence and procedural risks. This systematic review and meta-analysis shows that the extent of LA scarring after ablation is possibly associatedwith less AF recurrence after CA, paving the way for future research on ablation methods with lower chances of post-procedural recurrence. Substrate modification Previous studies in animal models have established the concept that “AF begets AF” by atrial remodeling. 18 In this manner, AF stimulates atrial fibrotic alterations that maintain and increase the AF burden, leading to a vicious cycle. 19 Furthermore, in spite of some limitations, studies in humans have shown that patients with paroxysmal AF have increased LA stiffness, possibly due to an increase in LA fibrosis. 20,21 629