Association Between Cardiac Surgeons’ Number of Years in Practice and Surgical Outcomes in New York Cardiac Centers

Key Points Question What is the association between cardiac surgeons’ years in practice and operative outcomes on coronary artery bypass grafting (CABG) and valve surgery? Findings In this cross-sectional study of data from early-career (<10 years) and late-career (>10 years) cardiac surgeons practicing between 2014 and 2016 in New York, a lower number of years in practice for cardiac surgeons was significantly associated with a higher risk-adjusted mortality rate in valve procedures. The risk-adjusted mortality rate was similar across different numbers of years in practice for CABG procedures. Meaning In this study, early-career status in cardiac surgeons was associated with worse surgical outcomes for valve operations, which suggests that additional complex valve surgery training in residency and mentorship guidance in early practice may be warranted.


Introduction
The association between surgeon experience and operative outcomes has been the subject of debate, with some studies suggesting worse outcomes with increasing surgeon age, 1-3 while others report the opposite. 4,5 A concave association, in which outcomes improve for the first number of years a surgeon is in practice, then plateau for a long period and worsen when surgeons approach retirement has also been reported. 3,6 Many of these studies have used surgeon age, which may be confounded by various factors, including different training pathways and medical school starting age, as a surrogate for surgeon experience. 4,[7][8][9] A few studies have used years in practice, which measures surgeon experience more precisely. 3,5 Most findings on this topic are based on investigations of general surgery cases. The association between surgeons' number of years in practice and outcomes remains unclear in cardiac surgery, which has high-risk operations that may warrant examination. A few studies in cardiac surgery have examined coronary artery bypass grafting (CABG) outcome variation with conflicting results. 1,4,7 However, to our knowledge, differences in the surgeon experience-outcome association for CABG and valve procedures have not yet been studied. Valve surgery carries a higher risk profile than CABG and is more often performed by more experienced surgeons. 9,10 With more than half of the US cardiothoracic surgeons older than 55 years and nearing retirement, 11 understanding this association is timely.

Methods
We obtained surgeon-level outcomes and case volume data from the publicly available 2014-2016 New York State Cardiac Data Reporting System. 10 Reported outcomes were observed mortality rate, expected mortality rate, and risk-adjusted mortality rate (RAMR) for isolated CABG and isolated valve or concomitant valve/CABG operations. All valve operations, excluding transcatheter procedures, were grouped into a single valve category in the New York State data. Both the expected mortality rate and RAMR were calculated from a multivariable risk model developed by the New York State Department of Public Health, accounting for patient demographic characteristics and comorbidities. 10 Mortality was defined as all-cause death within 30 days of surgery or within the index hospitalization, whichever was longer.
All surgeon-level data were collected from 2014-2016 New York State outcomes data, the latest New York State surgeon-level outcomes report. Data were analyzed in April 2020. This study followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline for cohort studies. Because the data were publicly available, the Yale institutional review board waived approval and the need for patient consent.
To determine surgeons' number of years in practice, we obtained each surgeon's medical school graduation year as well as residency and fellowship completion years from the Cardiothoracic Surgery Network website. 12 Each surgeon's final year of schooling was subtracted from 2016 (when the latest New York data were published) to determine number of years in practice. For surgeons whose training history was not listed on the Cardiothoracic Surgery Network website, we searched other online resources, such as the website of the surgeon's current hospital and the Healthgrades website. 13 We excluded international medical graduates because international medical graduates may have practiced as surgeons overseas, which may have obscured the actual years in practice. For

JAMA Network Open | Surgery
Association Between Cardiac Surgeons' Number of Years in Practice and Surgical Outcomes surgeons practicing at multiple hospitals, we combined surgeon-level outcomes at those hospitals. Surgeon years in practice were categorized as early career (<10 years) and late career (Ն10 years). The 10-year threshold was determined by the inflection point that occurred in the smoothed plot of risk-adjusted mortality and the number of years in practice.

Statistical Analysis
Statistical analysis was performed using surgeon-level outcome data, surgeon case volumes, and surgeon years in practice. Continuous variables were summarized by median (interquartile range [IQR]) and categorical variables by percentages. Wilcoxon rank sum test and χ 2 test were used to compare early-career with late-career surgeon status. We examined the association between surgeon-level RAMR and surgeon years of practice via linear regression models for CABG and valve procedures, adjusting for annual surgeon volume for respective case types. Years in practice was treated as a continuous variable and was modeled as a linear term for the CABG model and cubic term for the valve model to account for the nonlinear association with outcomes in valve operations.
Although cumulative case volume in a surgeon's career may mediate the association between experience and surgical outcomes, information on the cumulative case volume was not available in this cross-sectional data set. Therefore, such an association was not evaluated. All analyses were 2-tailed with statistical significance set at P < .05. Smoothed cubic spline associating mortality and the number of years was estimated using vcov package in Python 3.6 (Python Software Foundation).

Discussion
In this cross-sectional study using a large statewide data set, fewer years in practice was associated with worse risk-adjusted outcomes in valve surgery within the first 10 years in practice, but not for CABG. This finding was consistent after adjusting for case volume. In addition, extremely long years in practice was not associated with changes in outcome.
These findings are notable for several reasons. First, we were able to investigate the outcomes of valve operations in addition to CABG and show that these operations differ in their outcome association with surgeon experience, which, to our knowledge, has not been shown before. This Our results are consistent with studies reporting low case volume being associated with worse outcomes in valve surgery. 14,15 However, our finding that CABG outcomes are not significantly associated with surgeon experience differs from previous studies that have reported mixed results, some of which show worse outcomes for older surgeons and some of which show improved outcomes. 5,7,9 Two studies that found worse CABG outcomes to be associated with older surgeons used outcome data from 1989 to 1992 and from 1998 to 1999, 1,9 which may not reflect contemporary practice patterns and training paradigms. Tsugawa and colleagues 7 used Medicare data from 2011 to 2014 and reported that older surgeon status was associated with obtaining better CABG outcomes.

Limitations
This study has limitations. Our data set was a mandatory statewide outcome reporting system, which minimized potential selection bias or a narrow scope of payer-specific databases such as Medicare data. However, the limitations of this data set include the use of single-state data, which has a limited sample size of surgeons and may not represent states with practice and referral patterns different from New York. In addition, the valve surgery outcome data are reported as a combination of mitral, aortic, and tricuspid valve operations, and risk-adjusted outcomes for each valve operation type could not be evaluated. Valve and combined valve/CABG cases were also grouped into a single category such that these 2 case types could not be evaluated individually. The sample size of surgeons with less than 10 years in practice was 28 for the valve model, which could be subject to variability, although statistical tests show significant results. Further, a variety of factors may affect surgeon-level outcomes that we were not able to measure, such as cases with cosurgeons, number of revision operations, quality of residency training, and size of hospital program.

Conclusions
In this cross-sectional study, early-career status in surgeons with fewer than 10 years in practice have worse risk-adjusted mortality for valve operations but not for CABG surgery. These findings suggest that additional valve surgery training in residency or close mentorship for early-career surgeons on valve operations may be warranted.