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.