Relation of Race, Ethnicity and Cardiac Surgeons to Operative Mortality Rates in Primary Coronary Artery Bypass Grafting in California

The aim of this study was to evaluate whether African American, Hispanic, and Asian patients in California were more likely to undergo coronary artery bypass grafting (CABG) by cardiac surgeons with higher risk-adjusted mortality rates (RAMRs). Clinical data from the California CABG Outcomes Reporting Program were analyzed for all patients who underwent isolated CABG from 2003 to 2006 by surgeons who performed ≥10 operations. Surgeons were divided into quintiles on the basis of their RAMRs, with the top-performing surgeons in the first quintile and the lowest performing surgeons in the fifth quintile. There were 72,845 isolated CABG procedures performed by 303 surgeons, including 49,886 in white, 9,380 in Hispanic, 6,867 in Asian, and 2,750 in African American patients. African American and Asian patients underwent CABG by surgeons with higher mean RAMRs (2.90% and 2.99%, respectively) compared with the state average of 2.65% (p <0.001). Compared to white patients, Asian and Hispanic patients were more likely to be treated by surgeons in the lowest quintile (odds ratio [OR] 1.2, 95% confidence interval [CI] 1.11 to 1.3, and OR 1.38, 95% CI 1.30 to 1.48, respectively). African Americans and Hispanics were less likely to be operated on by surgeons in the top quintile compared to white patients (OR 0.80, 95% CI 0.71 to 0.90, and OR 0.81, 95% CI 0.76 to 0.87, respectively). Hispanics were less likely to be treated by surgeons in the top quintile than by surgeons in the lowest quintile (OR 0.65, 95% CI 0.60 to 0.75). In conclusion, racial and ethnic minority patients who undergo isolated CABG in California may be more likely to be operated on by cardiac surgeons with higher RAMRs.

Approximately 440,000 coronary artery bypass grafting (CABG) procedures are performed in the United States annually. Yet inadequate access to CABG has been documented for disadvantaged subpopulations, including racial and ethnic minorities. Even after controlling for the severity of disease and socioeconomic status, Hispanic and African American patients are less likely to undergo CABG than whites. When ethnic minorities do gain access to CABG, they may be more likely than whites to receive care from surgeons who have higher operative mortality rates. However, these findings are limited to selected geographic regions of the country and typically have excluded rapidly growing ethnic groups such as Asians and Hispanics. Therefore, in diverse racial and ethnic groups, the association between cardiac surgeons with higher operative mortality rates and patients’ race and ethnicity has not been fully investigated. In an effort to evaluate possible disparities in treatment by cardiac surgeons who performed isolated CABG in California, we investigated whether African Americans, Hispanics, and Asians were more likely than white patients to be operated on by surgeons with higher or lower 30-day risk-adjusted mortality rates (RAMRs).


Since January 2003, the California State Legislature has mandated that all nonfederal California-licensed hospitals providing cardiac surgery report all isolated and nonisolated CABG procedures to the Office of Statewide Health Planning and Development using a modified version of the Society of Thoracic Surgeons National Cardiac Surgery Database instrument. On a semiannual basis, all data are submitted electronically to the California CABG Outcomes Reporting Program (CCORP; Sacramento, California). These data include patient demographics, clinical characteristics, surgical provider, and observed mortalities. Detailed description of the CCORP data collection, adjudication process, and analysis method are described elsewhere. Race and ethnicity were self-reported by patients, and International Classification of Diseases, Ninth Revision, Clinical Modification, diagnosis and procedure codes were obtained by a data linkage process. Complete details on data verification process have been previously reported.

All patients who underwent isolated CABG in nonfederal California-licensed hospitals from January 1, 2003, to December 31, 2006, were identified. In addition, the cardiac surgeons of record for the procedures were noted for all cases. To maintain consistency with similar studies, surgeons with <10 isolated CABG surgeries across the specified time period were excluded from our analysis. Approximately 2/3 of all surgeons treated patients at ≤2 hospitals. In instances in which surgeons had performed cases in ≥2 hospitals, most of the surgeons’ cases (>70%) were performed at 1 institution. On the basis of this particular distribution, we could not separate surgeon-specific RAMRs from hospital effects.

The actual number of operative deaths from isolated CABG cases was defined as (1) death occurring in the hospital after CABG regardless of length of stay or (2) death occurring anywhere after hospital discharge but ≤30 days after CABG. To ensure accurate recording of deaths, these data were linked to vital statistics data from the California Department of Health Services to identify patients who died at home or at facilities other than the operating hospital ≤30 days after isolated CABG.

Using a multivariate logistic regression model, CCORP calculated and reported RAMRs and corresponding 95% confidence intervals (CIs) for all surgeons included in this study. The RAMR consists of an estimate of a surgeon’s underlying observed mortality rate divided by an estimate of the expected mortality rate for the surgeon given his or her case mix and then multiplied by the state average mortality rate. Risk adjustment considered differences in patients’ health before surgery using clinically meaningful preoperative risk factors associated with mortality. Development of the risk-adjusted mortality model has been previously described and validated. This form of standardization allowed a more accurate comparison between surgeons with different numbers of cases and those surgeons who treated sicker patients compared to healthier ones.

In this study, operative mortality performance was defined according to each surgeon’s RAMR. We characterized surgeons with lower RAMRs as having higher or “better” operative performance and surgeons with higher RAMRs as having lower or “worse” operative performance. Racial and ethnic classifications were based on federal standards. These designations were ascertained from medical records using the modified Society of Thoracic Surgeons data collection instrument that was reported to CCORP.

Baseline demographic and clinical characteristics were analyzed for the entire cohort and for 4 identified racial and ethnic subgroups (whites, African Americans, Hispanics, and Asians). Native Americans were excluded from the analysis because of the small number of patients despite aggregating data over multiple years. Differences in proportions among subgroups were compared using the chi-square test, and the means of continuous variables were examined with analysis of variance. Pearson’s correlation coefficients were calculated to examine the relation among cardiac surgeons’ RAMRs, patient volume, and patients’ race and ethnicity. Socioeconomic variables such as patient’s educational level, household income, and health insurance status were not available for analysis.

To maintain consistency with previously published studies on surgeons’ operative performance, the cohort of surgeons was divided into quintiles on the basis of their RAMRs, with the highest performing surgeons in the first quintile and the lowest performing surgeons in the fifth quintile. The distribution of patients by race and ethnicity was assessed for each operative mortality performance group to determine if minority patients were disproportionately treated by surgeons in the highest or lowest quintile. Comparisons between subgroups used white patients as the reference group to maintain consistency with previous reports that studied the effects of race and ethnicity on cardiovascular procedures. The likelihood of being treated by a surgeon in a respective quality performance group was determined by calculating unadjusted odds ratios (ORs), and statistical significance was determined by constructing the respective 95% CIs. Statistical analyses were conducted with SAS version 8.2 (SAS Institute Inc., Cary, North Carolina) and Stata version 10 (StataCorp LP, College Station, Texas).


A total of 72,845 isolated CABG procedures were performed at 121 hospitals by 303 cardiac surgeons during the study period. The cohort included 49,886 white patients (68%), 9,380 Hispanic patients (12.9%), 6,867 Asian patients (9.4%), and 2,750 African American patients (3.8%). Selected preoperative patient characteristics for each racial and ethnic group are listed in Table 1 . On average, white patients were older and had the lowest rates of co-morbidities such as diabetes mellitus, hypertension, heart failure, renal dysfunction, and moderate to severe mitral valve regurgitation. In contrast, African Americans were the youngest group but had the highest proportions of patients with hypertension, cerebrovascular accidents, moderate to severe mitral valve regurgitation, and heart failure and had the highest body mass indexes. Hispanic patients had the highest proportions of patients with diabetes mellitus and previous myocardial infarctions and the lowest mean ejection fraction at 47%. Asians had the lowest proportion of patients with cerebrovascular accidents and the lowest body mass indexes.

Table 1

Demographic and clinical characteristics for the cohort and individual racial and ethnic groups, 2003 to 2006

Variable Entire Cohort White African American Hispanic Asian p Value Overall
Patients 72,845 49,886 2,750 9,380 6,867
Age (years) 66.1 66.9 63.3 64.2 65.4 <0.0001
Body mass index (kg/m 2 ) 28.5 28.8 29.5 28.9 25.8 <0.0001
Creatinine (mmol/L) 1.30 1.28 1.37 1.33 1.33 <0.0001
Ejection fraction (%) 48.3 48.5 47.5 47.0 48.7 <0.0001
Women 26.1% 24.6% 40.1% 29.7% 26.6% <0.0001
Hypertension 80.5% 78.5% 89.6% 84.7% 86.2% <0.0001
Diabetes mellitus 39.8% 33.9% 48.0% 57.6% 50.4% <0.0001
Hepatic failure 0.4% 0.3% 0.5% 0.4% 0.3% NS
Atrial fibrillation 4.9% 5.5% 3.7% 3.1% 4.2% <0.0001
Cerebrovascular accident 12.8% 13.1% 14.8% 12.6% 11.7% <0.0001
Peripheral vascular disease 13.6% 14.1% 16.2% 14.3% 8.9% <0.0001
Myocardial infarct 48.2% 47.4% 53.5% 53.9% 44.1% <0.0001
Shock 2.3% 2.2% 2.0% 2.3% 2.4% NS
Heart failure 17.3% 16.1% 23% 21.7% 18.2% <0.0001
Ejection fraction <30% 8.8% 8.2% 10.3% 10.6% 9.3% <0.0001
New York Heart Association class IV 28.3% 28.2% 32.4% 30.3% 23.9% <0.0001
Previous CABG 4.2% 4.8% 3.7% 2.6% 2.3% <0.0001
Moderate/severe mitral valve regurgitation 3.7% 3.5% 4.7% 3.9% 4.5% 0.0011
Isolated CABG
Elective 35.9% 37.0% 31.8% 32.0% 36.6% <0.0001
Urgent 58.5% 57.3% 63.3% 62.5% 58.5% <0.0001
Emergency/salvage 5.6% 5.6% 4.9% 5.7% 4.9% NS
Left main coronary artery stenosis ≥50% 31.8% 32.2% 30.5% 30.8% 31.0% 0.0149
≥3 diseased coronary arteries 78.5% 78.0% 77.9% 79.2% 79.9% <0.0001
Internal mammary artery grafting 89.1% 89.1% 88.3% 88.6% 89.0% NS
Sustained ventricular tachycardia or ventricular fibrillation 2.2% 2.4% 2.4% 1.9% 1.8% 0.0003

Data are expressed as numbers, means, or percentages.

A p value >0.05 was considered nonsignificant.

African American and Asian patients had higher mean RAMRs (2.90% and 2.99%, respectively) compared to white (2.58%) and Hispanic (2.55%) patients or to the state average of 2.65% (p <0.001; Figure 1 ). When the cohort was separated into quintiles, the lowest operative performance group (quintile 5) had higher proportions of Hispanic and Asian patients (13.3% and 11.8%, respectively) than of African American and white patients (10.0% and 10.2%, respectively; Table 2 ). In contrast, the highest operative performance group (quintile 1) included the lowest proportions of Hispanic and African American patients (10.7% and 10.5%, respectively). Surgeon volume was not significantly associated with RAMR (Pearson’s correlation coefficient = −0.115, p = 0.24). Furthermore, the relation between surgeon volume and race and ethnicity was also not statistically significant (Pearson’s correlation coefficient = −0.017, p = 0.18).

Dec 22, 2016 | Posted by in CARDIOLOGY | Comments Off on Relation of Race, Ethnicity and Cardiac Surgeons to Operative Mortality Rates in Primary Coronary Artery Bypass Grafting in California

Full access? Get Clinical Tree

Get Clinical Tree app for offline access