Coronary Artery Bypass Grafting With Mitral Annuloplasty or Replacement for Ischemic Mitral Regurgitation in Medicare Beneficiaries.

Abstract

Retrospective studies of patients with ischemic mitral regurgitation (iMR) undergoing coronary artery bypass grafting (CABG) with concomitant mitral valve surgery frequently report improved survival with mitral valve repair/annuloplasty (MVr) over replacement (MVR). However, the only randomized controlled trial found no survival difference. Medicare claims data were queried to identify beneficiaries with iMR undergoing CABG/MVr or CABG/MVR. Kaplan-Meier estimates of survival after CABG/MVr and CABG/MVR were generated, and 20-year restricted mean survival times (RMSTs) were compared. Then, surgeons were stratified by their rate of CABG/MVr into groups with a demonstrated preference for MVr (PA) or MVR (PR). Outcomes were reanalyzed by surgeon preference. Overlap propensity score weighting was used for risk adjustment in all analyses. Among 10,471 beneficiaries with iMR, 6457 (61.7%) underwent CABG/MVr and 4014 (38.3%) underwent CABG/MVR. Risk-adjusted RMSTs were 6.02 years (95% CI, 5.77-6.26 years) after CABG/MVr and 5.57 years (95% CI, 5.33-5.81 years) after CABG/MVR (difference, 5.4 months; 95% CI, 1.2-9.4 months; P = .01). Among 1118 surgeons, 223 were PA surgeons (performed 2191 operations; 89.5% MVr rate) and 235 were PR surgeons (performed 1930 operations; 23.0% MVr rate). Risk-adjusted RMSTs were 5.76 years (95% CI, 5.36-6.15 years) vs 5.77 years (95% CI, 5.40-6.14 years) among beneficiaries undergoing surgery by PA surgeons and PR surgeons, respectively (difference, 0.1 years; 95% CI, -6.6 to 6.6 months, P = .964). In Medicare beneficiaries with iMR undergoing CABG/mitral valve surgery, CABG/MVr was associated with improved survival, even after risk adjustment for measured confounders. This may be due to unmeasured confounding variables affecting the decision to perform MVr or MVR, such as valvular pathology and/or severity of regurgitation. After endeavoring to account for unmeasured confounders using surgeon preference as an instrumental variable, surgeons who preferred CABG/MVr or CABG/MVR achieved similar long-term survival for their patients.