Background: Posterior pericardiotomy (PP) is a simple surgical technique that may reduce the risk of post-operative atrial fibrillation (POAF) by allowing for drainage of pericardial fluid into the left pleural space, reducing the incidence of pericardial effusion that may trigger POAF. Methods: This systematic review sought to determine the impact of posterior pericardiotomy on incidences of POAF, pericardial effusion, and the length of hospital stay after coronary artery bypass grafting (CABG). Electronic searches on PubMed, The Cochrane Library, EMBASE, EBSCO, Web of Science, and CINAHL databases from inception through December 15, 2018 were performed. The primary outcome of our study was reduction in POAF following PP. Secondary outcomes were reductions in pericardial effusion and length of hospital stay. A Mantel-Haenszel random effects model was used to summarize data across treatment arms. Heterogeneity between studies was assessed using the chi square test and was considered significant for p values < 0.10 or I 2 > 50%. Results: A total of 11 randomized controlled trials consisting of 2,462 patients undergoing CABG were included in the meta-analysis. Patients who underwent PP demonstrated significant reduction in POAF (OR 0.34; 95% CI 0.21-0.55, p < 0.001) and pericardial effusion (OR 0.11; 95% CI 0.06-0.20, p < 0.001) as compared to controls, respectively. However, heterogeneity between studies was significant (I 2 73% and 70%, respectively). No difference was observed in terms of length of hospital stay (standard mean difference -0.06; 95% CI -0.26 -0.14, p = 0.56; heterogeneity I 2 62%, p = 0.02). Number needed to treat to prevent POAF was 6.6 (95% CI 5. 38-8.39). Conclusion: Posterior pericardiotomy is a simple intraoperative technique that can reduce the risk of postoperative atrial fibrillation. These results should be interpreted with caution due to heterogeneity between the studies. 223Heart Failure with Preserved Ejection Fraction is a Highly Arrhythmogenic Disease