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Hospital volume doesn't explain racial disparity in cardiovascular procedure deaths

January 16, 2006

Results raise concerns about over-reliance on high volume as an indicator of health care quality
Although hospitals that perform fewer cardiovascular procedures tend to have higher death rates than higher-volume hospitals, and although African-American and Hispanic patients tend to be treated at lower-volume hospitals, differences in volume do not explain racial disparities in cardiovascular procedure death rates, according to a new study in the Jan. 17, 2006, issue of the Journal of the American College of Cardiology.

"Our results have two important implications: one, clinicians should recognize that black patients face markedly higher mortality after some cardiovascular procedures, with up to a two-fold increase in the risk of post-procedure death; and two, although better access to high-volume hospitals may improve outcomes for both white and minority patients, this increased use of high-volume hospitals is unlikely to eliminate racial differences in post-procedure mortality. Future research should explore other factors that could explain racial differences in death rates following these cardiovascular procedures and develop interventions to reduce these mortality rates," said Amal N. Trivedi, M.D., M.P.H., from Brigham and Women's Hospital and Harvard Medical School in Boston, Massachusetts.

Studies of health care quality have consistently indicated that "practice makes perfect;" that is, other things being equal, patients tend to fare better when they are treated by practitioners and institutions that perform a certain number of specific procedures per year. Since black and Hispanic patients are more likely to be treated at hospitals that perform fewer cardiovascular procedures, the volume-quality link was considered to be one possible explanation for higher death rates among minority patients following cardiovascular procedures.

The researchers focused in on that hypothesis by using data on hundreds of thousands of heart bypass surgeries, angioplasty procedures, abdominal aortic aneurysm repairs and carotid endarterectomy procedures performed from 1998 to 2001. The data were contained in the Nationwide Inpatient Sample, a collection of information from nearly 1,000 non-governmental hospitals across the United States.

The analysis confirmed that African-American and Hispanic patients were more likely to receive cardiovascular procedures at lower-volume hospitals. However, statistically adjusting for hospital volume did not significantly close the gap between black and white mortality. Hispanic patients in this database had about the same outcomes as white patients with similar conditions and risk factors.

Dr. Trivedi said that further studies are needed to explain why black patients are more likely to die after cardiovascular procedures.

"The primary limitation of this study is that we used administrative data from hospital discharges and did not have access to detailed clinical information. It is therefore possible that these unmeasured aspects of clinical severity may have partially explained some portion of the relationship between race, volume and post-procedure mortality," he said.

John S. Rumsfeld, M.D., Ph.D., F.A.C.C., from the Denver Veterans Affairs Medical Center and the University of Colorado Health Sciences Center in Denver, who co-authored an editorial in the journal with Andrew J. Epstein, Ph.D., M.P.P. from the Yale School of Public Health in New Haven, Connecticut, said the results of this study indicate that efforts to eliminate racial disparities in cardiovascular outcomes should focus on improving health care quality, not just sending minority patients to higher-volume hospitals.

"The study is important because it points us away from hospital procedure volume alone as a quality metric and as a target for quality improvement to eliminate racial disparities in outcome following cardiovascular procedures," Dr. Rumsfeld said. "At the same time, this study reinforces that there are racial disparities in outcome following cardiovascular procedures. Most likely, this means that racial minorities are receiving lower quality of care. This quality lies not so much in the hospital volume of procedures, but more likely in the skill of the individual operators, the skill of the care teams and in the systems of care at the hospitals."

American College of Cardiology