Background: American College of Cardiology/American Heart Association (ACC/AHA) Guidelines state that patients with an ejection fraction (EF) of 30% or less should not undergo mitral valve replacement for mitral regurgitation (MR). We sought to establish, using a national cardiac surgery database, whether patients with left ventricular dysfunction may safely undergo mitral valve surgery for MR, and if so, which ones.
Methods: We queried the Society of Thoracic Surgeons (STS) National Database to identify patients who had isolated mitral valve replacement or repair for MR between 1998 and 2001. Mortality and morbidity outcomes were compared by EF category (< or = 30% vs > 30%), and observed mortality compared by EF group, stratified by predicted risk for mortality. A classification and regression tree (CART) model was then used to determine which patient characteristics contributed most to designate the high-risk patient.
Results: Of the 14,582 patients who had mitral valve surgery, 727 had an EF of 30% or less and 13,855 had an EF of more than 30%. Observed mortality rates were higher for patients with an EF of 30% or less (5.4% vs 3.1%). However, for low-risk to medium-risk patients, mortality rates remained fairly constant across levels of EF. Mortality is notably increased in the high-risk patients (predicted risk > 10%). A classification tree identifies three key characteristics for high risk: age more than 75 years, renal failure, and emergent or salvage procedure.
Conclusions: When the predicted mortality risk is less than 10%, EF has minimal impact on operative mortality for mitral regurgitation. In contrast to the ACC/AHA Guidelines, our data show that operative risk for mitral valve surgery is not prohibitive for most patients with ventricular dysfunction.