Should The Mitral Valve Be Repaired For Moderate Ischemic Mitral Regurgitation With Coronary Artery Bypass Grafting?A Meta-analysis

Objective:Ischemic mitral regurgitation(IMR)is a common complication after myocardial infarction in patients with coronary heart disease,and is associated with increased mortality and recurrent congestive heart failure.Due to the complexity of the pathophysiological mechanism of IMR,the surgical treatment strategy of IMR is currently an important problem.The current controversy surrounds the appropriate surgical management for moderate IMR.The purpose of this study was to review the literature on moderate IMR for meta-analysis,and to evaluate the importance and necessity of performing mitral valve surgery in patients with moderate IMR during coronary artery bypass grafting by comparing the short-term and long-term outcomes of the CABG alone group and the MVS plus CABG group.Methods:A computerized search was performed using Pub Med,Cochrane Library,Embase,CNKI,VIP and Wanfang database,and supplemented by manual search.Stata12.0 statistical software was used for analyzing the outcomes of primary endpoint(early mortality[death within 30 days after operation or before discharge],long-term survival)and secondary endpoint(NYHA functional classes,mitral regurgitation grades and echocardiographic characteristic of the left ventricle).Results:A total of 747 studies were detected from establishment of the databases to November 2019 and finally eleven studies with a total of 1977 patients were included(CABG alone=1401 and MVS plus CABG=576).Among all studies,four RCTs and seven retrospective studies were identified.Analysis of all studies showed an increased risk of early mortality in the MVS plus CABG group(OR:2.00,95%CI:1.28-3.13,P=0.002).However,an analysis of four RCTs only showed that the risk of early mortality was comparable between the two groups(OR:0.85,95%CI:0.24-3.00,P=0.804).There was no difference in long-term survival between the two groups(HR:1.04,95%CI:0.83-1.32,P=0.714).There was significantly greater improvement on residual MR grade in the MVS plus CABG group(OR:0.22,95%CI:0.09-0.53,P=0.001),although moderate heterogeneity was found in the studies(I~2=68.0%,P=0.003).There was no difference in NYHA functional classes between the two groups(OR:0.82,95%CI:0.40-1.71,P=0.602).No difference in postoperative LVEF(SMD:-0.11,95%CI:-0.43-0.20,P=0.483),LVESD(SMD:0.07,95%CI:-0.51-0.66,P=0.808)or LVEDD(SMD:0.05,95%CI:-0.46-0.56,P=0.860)was found.However,the postoperative NYHA functional classes and LVEF of the two groups was significantly improved compared with those before surgery,and the differences were statistically significant(P<0.05).Conclusion:In patients with moderate IMR,adding mitral valve surgery to Coronary Artery Bypass Grafting is safe,and it can significantly reduce the residual MR grade after surgery.However,it lacks definitive evidence to show that adding MVS has a positive efficacy on functional classes,left ventricular reverse remodeling and long-term survival benefits.RCTs with larger sample size and longer follow-up duration are required to further assess the efficacy of MVS in patients with moderate IMR.