Endovascular technology, hospital volume, and mortality with abdominal aortic aneurysm surgery
Received 12 October 2007; accepted 26 January 2008. published online 28 April 2008.
Objective
To determine whether the introduction of endovascular technology changed the relationship of hospital volume to mortality with abdominal aortic aneurysm repair.
Methods
Data from all hospitals in the United States that performed abdominal aortic aneurysm surgery on Medicare patients from 2001 to 2003 were obtained from the national Medicare database. The primary outcome variable was death ≤30 days of operation or before hospital discharge. We determined the effect of total hospital volume on operative mortality for all types of repair and for endovascular and open repair separately. All analyses were adjusted for patient risk using logistic regression.
Results
The proportion of abdominal aortic aneurysms repaired with an endovascular approach increased from 27% to 39% during the 3-year study period. Hospital volume was significantly related to operative mortality in all comparisons. Mortality rates were 80% higher at hospitals in the lowest vs the highest quartile of total volume (odds ratio [OR], 1.81; 95% confidence interval [CI], 1.62-2.04) when considering all types of repair together. A similar relationship between total hospital volume and mortality was found when separately examining open repair (OR, 1.52; 95% CI, 1.33-1.73) and endovascular repair (OR, 1.68; 95% CI, 1.32-2.22). Higher-volume hospitals were more likely to use the endovascular approach. The highest-volume hospitals used the endovascular approach 44% of the time compared with only 18% at the lowest-volume hospitals. This greater use of the endovascular procedure at high-volume hospitals accounted for 37% of the difference in mortality between high- and low-volume hospitals.
Conclusion
As the endovascular repair becomes more widespread, the relationship between hospital volume and operative mortality still remains. High-volume hospitals are more likely to use the endovascular approach, and this explains a significant portion of the observed impact of hospital volume on mortality.
Michigan Surgical Collaborative for Outcomes Research and Evaluation (M-SCORE) and the Division of Vascular Surgery, Department of Surgery, University of Michigan Medical Center, Ann Arbor, Mich.
Reprint requests: Justin B. Dimick, MD, MPH, M-SCORE Offices, 211 N. Fourth Ave, Ste 301, Ann Arbor, MI 48104.
Competition of interest: Dr Dimick has served as a paid research consultant for the Leapfrog Group, a coalition of private payers, who advocate selective referral to high-volume hospitals for abdominal aortic aneurysm repair and other high-risk operations.
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