Objective: Focusing on 3-dimensional mitral valve structure, this study investigated predictors for moderate ischemic mitral regurgitation (IMR) improvement after off-pump coronary artery bypass grafting (OPCAB).Methods: This study included 143 patients (age 67.6 ± 7. 6 years, 32.9% female) with previous myocardial infarction and moderate IMR undergoing OPCAB. Preoperative 3-dimensional echocardiographic data were analyzed, focusing on mitral annular geometry and leaflet tethering model. Patients were grouped according to IMR at 1-year postoperative follow-up into improved (n = 65), with no or mild IMR, and failure (n = 70), with moderate or severe IMR, groups. Groups were compared to identify predictors of IMR improvement after OPCAB.Results: Eight patients died within 1 year. At 1 postoperative year, improved group included 65 patients; failure group included 70. Improved group had less preoperative annular flattening (smaller nonplanar angle) and segmental leaflet tethering (smaller A3, P1, P2, and P3 tethering angles) than failure group. Nonplanar angle (P