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Outcomes/Effectiveness Research

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Variation in outcomes is small for CABG surgery patients treated at high-volume vs. lower volume hospitals

Many studies have shown that patients who undergo coronary artery bypass graft (CABG) surgery at high-volume hospitals that perform 500 or more such surgeries each year fare better than patients treated at lower volume hospitals. Nevertheless, patients or health plans looking for a hospital that performs high-quality CABG surgery should not equate CABG quality solely with the volume of CABG surgeries a hospital performs, cautions University of Pennsylvania investigator, Andrew J. Epstein, M.P.P.

In a study supported by the Agency for Healthcare Research and Quality (National Research Service Award training grant T32 HS00009), the researchers retrospectively analyzed the Nationwide Inpatient Sample database (national sample of hospitalizations in acute care hospitals) for 228,738 patients who underwent CABG surgery in 1998-2000 at low (12-249 cases/year), medium (250-499 cases/year), and high (500 or more cases/year) CABG volume hospitals.

Overall, 4.21 percent of CABG patients in low-volume hospitals died compared with 3.74 percent in medium-volume hospitals and 3.54 percent in high-volume hospitals, a small difference in mortality. After adjusting for other factors, there was a significant 29 percent increased risk of death for patients of low-volume hospitals, but there was an 11 percent (borderline significant) increased risk at medium-volume hospitals. On the other hand, most low-volume (85 percent) and medium-volume (89 percent) hospitals achieved comparable or better outcomes than predicted given the severity of illness of their patients, while only 6 percent of high-volume hospitals accomplished this. These findings raise concerns about the adoption of a hospital CABG volume recommendation of 500 annual cases as an effective means of ensuring high-quality care.

See "Hospital coronary artery bypass graft surgery volume and patient mortality, 1998-2000," by Saif S. Rathore, M.P.H., Mr. Epstein, Kevin G. Volpp, M.D., Ph.D., and Harlan M. Krumholz, M.D., S.M., in the January 2004 Annals of Surgery 239(1), pp. 110-117.

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