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Original Article
April 2008

Volume-Outcome Relationship for Coronary Artery Bypass Grafting in an Era of Decreasing Volume

Author Affiliations

Author Affiliations: Department of Surgery, Medical School (Drs Ricciardi, Virnig, Ogilvie, and Dahlberg), and Division of Health Services Research, School of Public Health (Dr Virnig), University of Minnesota, Minneapolis; Division of Clinical Care Research, Department of Medicine, New England Medical Center, Tufts University School of Medicine, Boston, Massachusetts (Dr Selker); and Department of Surgery, St Michael's Hospital, University of Toronto, Toronto, Ontario, Canada (Dr Baxter). Dr Ricciardi is now with the Department of Colon and Rectal Surgery, Lahey Clinic, Tufts University, Burlington, Massachusetts.

Arch Surg. 2008;143(4):338-344. doi:10.1001/archsurg.143.4.338

Hypothesis  We hypothesized that the recent reduction in procedure volume for coronary artery bypass grafting (CABG) has led to an increase in the in-hospital mortality rate.

Design  Hospital discharge data from the Nationwide Inpatient Sample from January 1, 1988, through December 31, 2003.

Setting  A 20% random sample of patients admitted to US hospitals.

Patients  All patients who underwent CABG or percutaneous transluminal coronary interventions. Facilities performing CABG were assigned to standard volume cutoffs.

Main Outcome Measures  Rates of cardiac procedures and the proportion of hospitals meeting standard volume cutoffs, as well as the CABG mortality rate.

Results  During our 16-year study period, the rate of CABG increased from 7.2 cases per 1000 discharges in 1988 to 12.2 cases in 1997 but then decreased to 9.1 cases in 2003, while the rate of percutaneous interventions tripled. For CABG, the proportion of high-volume hospitals declined from 32.5% in 1997 to 15.5% in 2003. Despite shifts between high- and low-volume hospitals, the CABG mortality rate steadily declined from 5.4% in 1988 to 3.3% in 2003. Hospitals performing the lowest volume of CABG experienced the largest decrease in the in-hospital mortality rate.

Conclusions  Since 1997, CABG volume has declined in the setting of a decrease in in-hospital mortality. A lower mortality rate in the setting of reduced CABG volume is a counterintuitive finding, suggesting that procedure volume is an insufficient predictor of outcome on which to base regionalization strategies.