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CLINICAL STUDY: CORONARY BYPASS SURGERY

The role of hospital volume in coronary artery bypass grafting: is more always better?¹

^a Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan, USA
^b Health Services Research and Development Field Program, Veterans Administration Medical Center, Ann Arbor, Michigan, USA
^c Department of Medicine, University of Washington School of Medicine, Seattle, Washington, USA

Manuscript received January 23, 2001; revised manuscript received August 8, 2001, accepted August 22, 2001.

^* Reprint requests and correspondence: Dr. Kim A. Eagle, Division of Cardiovascular Disease, Department of Internal Medicine, University of Michigan Medical Center, 3910 Taubman Center, Ann Arbor, Michigan 48109-0366, USA.
keagle{at}umich.edu

OBJECTIVES: The goal of this study was to determine whether outcomes of nonemergent coronary artery bypass grafting (CABG) differed between low- and high-volume hospitals in patients at different levels of surgical risk.

BACKGROUND: Regionalizing all CABG surgeries from low- to high-volume hospitals could improve surgical outcomes but reduce patient access and choice. "Targeted" regionalization could be a reasonable alternative, however, if subgroups of patients that would clearly benefit from care at high-volume hospitals could be identified.

METHODS: We assessed outcomes of CABG at 56 U.S. hospitals using 1997 administrative and clinical data from Solucient EXPLORE, a national outcomes benchmarking database. Predicted in-hospital mortality rates for subjects were calculated using a logistic regression model, and subjects were classified into five groups based on surgical risk: minimal (<0.5%), low (0.5% to 2%), moderate (2% to 5%), high (5% to 20%), and severe (20%). We assessed differences in in-hospital mortality, hospital costs and length of stay between low- and high-volume facilities (defined as 200 annual cases) in each of the five risk groups.

RESULTS: A total of 2,029 subjects who underwent CABG at 25 low-volume hospitals and 11,615 subjects who underwent CABG at 31 high-volume hospitals were identified. Significant differences in in-hospital mortality were seen between low- and high-volume facilities in subjects at moderate (5.3% vs. 2.2%; p = 0.007) and high risk (22.6% vs. 11.9%; p = 0.0026) but not in those at minimal, low or severe risk. Hospital costs and lengths of stay were similar across each of the five risk groups. Based on these results, targeted regionalization of subjects at moderate risk or higher to high-volume hospitals would have resulted in an estimated 370 transfers and avoided 16 deaths; in contrast, full regionalization would have led to 2,029 transfers and avoided 20 deaths.

CONCLUSIONS: Targeted regionalization might be a feasible strategy for balancing the clinical benefits of regionalization with patients’ desires for choice and access.

Abbreviations and Acronyms   APR-DRG   All Patient Refined-Diagnosis Related Groups   CABG   coronary artery bypass grafting   DRG   diagnosis related group   ICD-9-CM   International Classification of Diseases, Ninth Edition

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