Meta-analysis of concomitant mitral valve repair and coronary artery bypass surgery versus isolated coronary artery bypass surgery in patients with moderate ischaemic mitral regurgitation

Ischaemic mitral regurgitation (IMR) is a complication of coronary artery disease with normal chordal and leaflet morphology. Controversy surrounds the issue of appropriate surgical management of moderate IMR. With the present meta-analysis, we aimed to determine whether the addition of mitral valve (MV) repair to coronary artery bypass grafting (CABG) improved clinical outcome over CABG alone in patients with moderate IMR. Databases were searched for studies reporting on clinical outcomes after CABG and MV repair or CABG alone for moderate IMR. Clinical end-points were operative mortality, survival, New York Heart Association (NYHA) class ≥2 and MR grade ≥2 at last follow-up. A total of five observational and four randomized controlled trials (RCTs) were identified. The mean follow-up was 2.7 years. An analysis of all studies revealed increased operative risk in the concomitant CABG and MV repair group {risk ratio [RR] 2.02 [95% confidence interval (CI) 1.15, 3.56], P = 0.01, I(2) = 0%}. However, an analysis of RCTs only showed that the operative risk was equivalent [RR 1.05 (95% CI 0.34, 3.30), P = 0.93, I(2) = 0%]. Pooled hazard ratio (HR) on survival did not favour either procedure [all studies: HR 1.08 (95% CI 0.77, 1.50), P = 0.66, I(2) = 0%; RCTs only: HR 0.89 (95% CI 0.47, 1.70), P = 0.73, I(2) = 0%]. The incidence of exercise intolerance quantified as NYHA class ≥2 was similar between groups (all studies: RR 0.72 (95% CI 0.42, 1.24), P = 0.24, I(2) = 77%; RCTs only: RR 0.61 (95% CI 0.24, 1.55), P = 0.30, I(2) = 83%]. Risk of residual MR grade ≥2 was higher in the CABG only group [all studies: RR 0.30 (95% CI 0.16, 0.60), P < 0.001, I(2) = 83%; RCTs only: RR 0.20 (95% CI 0.04, 0.90), P = 0.04, I(2) = 72%]. There is neither increased operative mortality nor survival benefit associated with concomitant CABG and MV repair for IMR of moderate degree over CABG alone. Further studies with long-term follow-up data and sub-group analyses of current data are needed to define a subset of patients whose survival and functional status may improve with the concomitant MV repair.