The Challenge of Achieving 1% Operative Mortality for Coronary Artery Bypass Grafting: A Multi-Institution Society of Thoracic Surgeons Database Analysis

OBJECTIVES:

Cardiothoracic surgical leadership recently challenged the surgical community to achieve an operative mortality rate of 1.0% for the performance of isolated coronary artery bypass grafting (CABG). The possibility of achieving this goal remains unknown due to the increasing number of high-risk patients being referred for CABG. The purpose of our study was to identify a patient population in which this operative mortality goal is achievable relative to the estimated operative risk.

METHODS:

Patient records from a multi-institution (17 centers) Society of Thoracic Surgeons (STS) database for primary, isolated CABG operations (2001-2012) were analyzed. Multiple logistic regression modeling with spline functions for calculated STS predicted risk of mortality (PROM) was used to rigorously assess the relationship between estimated patient risk and operative mortality, adjusted for operative year and surgeon volume.

RESULTS:

A total of 34,416 patients (average patient age, 63.9 ± 10.7 years; 27% [n = 9190] women) incurred an operative mortality rate of 1.87%. Median STS predicted risk of mortality was 1.06% (interquartile range, 0.60%-2.13%) and median surgeon CABG volume was 544 (interquartile range, 303-930) operations over the study period. After risk adjustment for the confounding influence of surgeon volume and operative year, the association between STS PROM and operative mortality was highly significant (P < .0001). More importantly, the adjusted spline function revealed that an STS PROM threshold value of 1.27% correlated with a 1.0% probability of death, accounting for 57.3% (n = 19,720) of the total study population. Further, the STS PROM demonstrated a limited predictive capacity for operative mortality for STS PROM > 25% as observed to expected mortality began to diverge.

CONCLUSIONS:

Achieving the goal of 1.0% operative mortality for primary, isolated CABG is feasible in appropriately selected patients in the modern surgical era. However, this goal may be achieved in only 60% of CABG patients without other improvements in processes of care. CalculatedSTS PROM can be used to strongly identify patients with estimated mortality risk <1.27% to achieve this goal, but it appears limited in its predictive capacity for those patients with estimated risk >25.0%. These data provide a foundation for further study to determine if 1.0% mortality for CABG is achievable nationwide.