Case volume in cardiac surgery has been a concern since the term “the occasional open heart surgeon” was used more than 40 years ago, indicating one who performs cardiac surgery infrequently.Methods
Risk-adjusted operative mortality (in-hospital or 30-day mortality) for isolated coronary artery bypass grafting procedures reported to the California CABG Outcomes Reporting Program for 2003-2004 was determined by surgeon and by hospital. Standard Society of Thoracic Surgeons item definitions were used. A total of 49,421 coronary artery bypass grafting (40,377 isolated) procedures were performed by 302 surgeons at 121 hospitals. Low-volume surgeons (n = 117) were defined as performing a total of less than 1 coronary artery bypass grafting (isolated or nonisolated) procedure per week at all hospitals (mean ± standard deviation, 22 ± 15/y). High-volume surgeons (n = 185) performed a total of 1 or more cases per week (mean ± standard deviation, 120 ± 62/y). Logistic regression and hierarchic analysis were used to compare volume cohorts.Results
The overall risk-adjusted mortality rate was 3.62% for low-volume and 3.02% for high-volume surgeons. Analysis by surgeon per hospital produced 610 surgeon-hospital pairs. The lowest risk-adjusted mortality rates were found among surgeons performing more than 1 procedure per week at a single hospital (2.70%). When high-volume surgeons performed less than 1 procedure per week at a hospital, their mortality rates were similar to those of low-volume surgeons (3.39%-4.11%). High-volume surgeons performing procedures at multiple sites had higher mortality than high-volume surgeons working at a single institution.Conclusion
A high-volume surgeon becomes an “occasional open heart surgeon” when working at multiple hospitals and performing a small volume of procedures at some of them. This study suggests that volume is not as important as processes of care in determining outcomes of coronary artery bypass grafting procedures and that system factors might be more important to outcomes than surgeon experience.