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Both low- and high-risk patients benefit from undergoing coronary bypass surgery at high-volume hospitals

Evidence shows that individuals who undergo coronary artery bypass graft (CABG) surgery at hospitals that perform many such surgeries each year are less likely to die after the surgery than those who have the surgery done at low-volume hospitals. However, patient risk factors may influence the level of benefit gained from having the surgery done at high-volume centers, suggests a study supported by the Agency for Healthcare Research and Quality (HS11295).

The researchers found that patients at very low risk (less than 0.5 percent) of dying were 60 percent less likely and those at low risk (0.5-2 percent) were 25 percent less likely to die in the hospital after CABG surgery at high-volume centers (more than 500 cases/year) compared with low-volume centers.

Very high risk (greater than 10 percent) patients had only 13 percent less likelihood of dying at high- versus low-volume hospitals, while the highest risk patients (risk of dying greater than 24 percent) had better outcomes at high-volume centers. If this study of CABG patients in New York is validated by other studies, the practice of referring low-risk patients to community hospitals with low operative volumes and selectively referring only high-risk patients to high-volume, high-expertise centers may need to be reevaluated, suggests Laurent G. Glance, M.D., of the University of Rochester Medical Center. Dr. Glance cautions, however, that volume is an imperfect proxy for quality of care and should not be used as the sole basis for regionalizing care.

For this study, the researchers retrospectively analyzed data from the Cardiac Surgery Reporting System database on all patients undergoing CABG surgery in New York State who were discharged in 1996. They examined in-hospital mortality as a function of hospital procedure volume, after adjusting for severity of disease.

More details are in "Is the hospital volume-mortality relationship in coronary artery bypass surgery the same for low-risk versus high-risk patients?" by Dr. Glance, Andrew W. Dick, Ph.D., Dana B. Mukamel, Ph.D., and Turner M. Osler, M.D., F.A.C.S., in the Annals of Thoracic Surgery 76, pp. 1155-1162, 2003.

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