Introduction
Ischemic mitral regurgitation (IMR) is a frequent complication of coronary artery disease, which is associated with increased left ventricular (LV) dysfunction and mortality [1, 2]. Most experts in mitral surgery advocate for concomitant correction of more than moderate IMR during coronary bypass surgery. However, the choice of mitral valve repair (MVr) or mitral valve replacement (MVR) is controversial [3-5]. Mitral valve repair has been associated with lower hospital mortality and greater late survival compared to replacement in patients with degenerative mitral valve disease [6, 7]. In contrast, the benefits of mitral valve (MV) repair compared to replacement in patients with IMR are not as well defined. Several retrospective studies suggested lower operative mortality and better long-term survival with repair compared to replacement in patients with IMR [8-15]. However, these studies are largely limited by inherent selection bias in favor of repair. Indeed, a recent randomized controlled trial (RCT) [16], which compared MV repair versus replacement in patients with IMR showed equivalent operative mortality and short-term survival but better freedom from recurrent mitral regurgitation (MR) with MV replacement. The purpose of this study is to compare mortality and major morbidities after MV repair or replacement for IMR while accounting for all known confounders using rigorous regression methodology with validation of multivariable analysis by bootstrapping, and evaluation of the regression model for discrimination, calibration, and multicollinearity.