Objectives: Older studies of coronary artery bypass (CABG) institutional case volumes and outcomes (V/O) reported conflicting results. We explored this association in the rapidly changing contemporary practice of American surgeons using the Society of Thoracic Surgeons Adult Cardiac Surgery Database (STS-ACSD).

Methods: The 2018-2019 isolated primary coronary artery bypass grafting (CABG) experience in the STS-ACSD was analyzed (241,902 patients; 1,014 hospitals; 2,718 surgeons). Generalized Estimating Equations were used to estimate coefficients between CABG institutional case volumes and outcomes. The observed to expected (O/E) ratios based on STS risk models were used to assess risk-adjusted operative mortality (OM), mortality/major morbidity (MM) and deep sternal wound infections (DSWI) as a function of institutional case volumes.

Results: Mean (SD) OM, MM and DSWI rates were 2.1%(2.7), 11.1%(9.2) and 0.6%,(0.5), respectively. Mean (SD) institutional case volumes per study period was 239(192). 23% and 9% of institutions performed <100 and >500 cases/study period, respectively. There was a weak negative correlation between expected mortality (R2- 0.0014), OM (R2-0.0272), MM (R2 -0.1213), and DSWI (R2-0.003) and institutional case volumes.

Conclusion: CABG outcomes generally improve with increasing institutional case volumes. Given the large number of CABG cases performed nationally, even the documented weak correlation has the potential to appreciably decrease OM, MM and DSWI if cases are performed at higher volume institutions. Studies focusing on additional hospital and surgeon factors are warranted to further define quality improvement opportunities.

Keywords: CABG institutional case volumes; outcomes; quality.