Perioperative deaths after mitral valve operations may be overestimated by contemporary risk models

Background: Percutaneous therapies to manage mitral regurgitation are emerging as an alternative to conventional operations, especially for patients with a high estimated perioperative risk. However, contemporary risk models may not accurately reflect outcomes at reference mitral valve centers. The purpose of this study was to describe perioperative mortality rates after mitral valve operations in a contemporary cohort.

Methods: Between 2001 and 2011, 1,154 patients underwent mitral valve operations at a reference center. Of these, 851 underwent repair and 303 underwent replacement. Concomitant coronary artery bypass grafting was performed in 201 (17%). The Society of Thoracic Surgeons (STS) risk score version 2.73 and European System for Cardiac Operative Risk Evaluation (EuroSCORE) II were used to estimate the number of perioperative deaths.

Results: The observed perioperative mortality was 1.0%. The STS score was 2.3%±2.6% and was higher than the observed mortality rate for each of the STS subgroups (all p<0.001). The EuroSCORE II expected mortality was 3.0%±3.4% and was greater than the observed mortality rate for isolated and combined procedures (both p<0.001). The STS and EuroSCORE II provided fair death discrimination, with an area under the receiver operating characteristic curve of 0.74 and 0.67, respectively.

Conclusions: Although current risk models aid in risk stratifying patients, the contemporary perioperative mortality rate at a reference mitral valve center is significantly lower than expected. The use of alternate therapies must therefore take into consideration differences in perioperative risk based on the treating center.