Volume-Outcome Relationship of Resternotomy Coronary Artery Bypass Grafting

We assessed volume-outcome relationships of resternotomy coronary artery bypass grafting (CABG). We studied over 1M first-time CABG and about 100K resternotomy CABG patients between 2010 and 2019. Primary outcomes were in-hospital mortality and mortality and morbidity (M&M) rates calculated per hospital and per surgeon. Outcomes were compared across 6 total cardiac surgery volume categories. Multivariable generalized linear mixed-effects models were used considering continuous case volume as the main exposure, adjusting for patient characteristics and within-surgeon and hospital variation.

We observed a decline in resternotomy CABG mortality and M&M from the lowest to the highest case-volume categories. Looking at outcomes vs. continuous volume showed that beyond a minimum annual volume (hospital 200-300 cases; surgeon 100-150 cases, approximately), mortality and M&M rates did not further improve. Using individual-level data and adjusting for patient characteristics and clustering within surgeon and hospital, we found higher procedural volume was associated with improved surgeon-level outcomes. Hospital-level adjusted volume-outcomes associations were not statistically significant.

We observed an inverse relationship between total cardiac case volume and resternotomy CABG outcomes at the surgeon level only, indicating that individual surgeon’s experience, rather than institutional volume, is the key determinant.