Mitral regurgitation progression following isolated coronary artery bypass surgery: frequency, risk factors, and potential prevention strategies.

BACKGROUND Though de novo mitral regurgitation (MR) is frequently seen in patients who have undergone coronary artery bypass surgery (CABG), its incidence, predictors, and mechanisms are not known. METHODS Our surgical registry was screened for patients undergoing isolated CABG who had preoperative and postoperative resting echocardiograms performed at our institution with <or=2+ MR preoperatively. This yielded 438 patients. Progression to 3-4+ MR post-CABG was correlated with clinical, electrocardiographic, echocardiographic, and operative variables. RESULTS New 3-4+ MR developed in 11 (10%) of the 108 patients with no prior MR, 21 of the 180 (12%) patients with pre-CABG 1+ MR, and 37 of the 150 (25%) patients with pre-CABG 2+ MR. MR progression correlated with female gender (42% vs 27%, p=0.01), history of renal insufficiency (12% vs 5%, p=0.05), prior-CABG (30% vs 17%, p=0.01), lack of beta-blocker use (19% vs 35%, p=0.008), lower incidence of significant PDA stenosis grafted (88% vs 98%, p=0.003), lower preoperative LVEF (42+/-19% vs 50+/-17%, p=0.001), larger LV size (p=0.01), pre-CABG MR grade (p=0.0002), and pre-CABG presence of LBBB block (20% vs 4%, p<0.0001). Independent predictors of MR progression, pre-CABG, were female gender (p=0.002), history of renal insufficiency (p=0.05), lack of beta-blocker use (p=0.006), MR grade (p=0.02), and presence of LBBB (p=0.005). CONCLUSION Development of significant MR following isolated CABG is common and may be related to incomplete myocardium revascularization, especially in the PDA area and LV remodeling. Preoperative, beta-blocker use may be protective against its development.