Mitral Valve Repair During CABG Surgery: Navigating the Gray Area of Moderate Ischemic Mitral Regurgitation

Ischemic mitral regurgitation is a consequence of prior myocardial infarction, resulting in regional wall motion abnormalities, leaflet tethering, papillary muscle displacement, and annular dilatation. In patients with multivessel coronary artery disease, approximately 30-50% develop moderate to severe ischemic mitral regurgitation, associated with a threefold increase in the incidence of congestive heart failure and cardiac death. We present a case involving a 66-year-old male with multivessel coronary artery disease, heart failure with reduced ejection fraction (30-35%), and diabetes who was found to have moderate ischemic mitral regurgitation at the time of coronary artery bypass graft surgery. The decision to pursue mitral valve repair was deferred. Despite revascularization, the patient had persistent mitral regurgitation and a low ejection fraction, leading to an inability to wean off cardiopulmonary bypass. Subsequently, an intra-aortic balloon pump was deployed, and due to further deterioration, mechanical cardiac support was escalated to an Impella 5.5 (Abiomed). After a prolonged hospital course, the patient was ultimately discharged to a skilled nursing facility. This case highlights the complex decision-making involved in pursuing mitral valve repair in patients with moderate ischemic mitral regurgitation and reduced ejection fraction, given the extended aortic cross-clamping time and the associated increase in perioperative risks. Considering these challenges, there needs to be careful selection of patients who should undergo mitral valve repair in addition to revascularization versus revascularization alone. Selecting these patients requires the assessment of multiple factors, including viability, scar burden, scar location, left ventricular size, and careful pre-operative grading of the severity of mitral regurgitation. In this case report, we highlight the significance of scar in the coronary distribution that supplies the posteromedial papillary muscle, leading to persistent ischemic mitral regurgitation after coronary artery bypass grafting despite having over 75% of myocardial viability on positron emission tomography imaging.