Measure What Matters: Institutional Outcome Data Are Superior to the Use of Surrogate Markers to Define “Center of Excellence” for Abdominal Aortic Aneurysm Repair

Abstract

Outcome analysis is increasingly being used to develop health-care policy and direct patient referral. For example, the Leapfrog Group health-care quality initiative has proposed "evidence-based hospital" referral criteria for specific procedures including elective abdominal aortic aneurysm repair (AAA-R). These criteria include an annual hospital AAA operative volume exceeding 50 cases and provision of intensive care unit (ICU) care by board-certified intensivists. Outcomes after AAA-R are reportedly influenced by presentation (intact vs. ruptured), operative approach (endovascular vs. open, transperitoneal vs. retroperitoneal), surgeon subspecialty, case volume (hospital and surgeon), and provision of postoperative care by an intensivist. The purpose of this study was to compare our single-center results with those of high-volume centers to assess the validity of the concept that surrogate markers, such as case volume or intensivist involvement, can be used to estimate procedural outcome. A retrospective review was performed of AAA-Rs at one low-volume academic medical center from January 1994 to March 2005. Demographic data, aneurysm diameter and location, operative indications, and repair approach were documented. Postoperative complications, mortality rates, and hospital and ICU length of stay (LOS) were noted and compared to established benchmarks. During the study period, 270 patients underwent AAA-R (annual mean = 27 hospital cases and 13.4 cases/attending vascular surgeon). ICU care was provided by a dedicated vascular surgery service without routine intensivist involvement. Open, elective, infrarenal AAA-R was performed in 161 patients (60%), with a 2.5% hospital mortality rate (30-day, 3.1%). Thirty-three (12%) patients underwent elective endovascular aneurysm repair (EVAR), with no mortality. Both ICU (3.7 vs. 1.4 days, p = 0.03) and hospital (9.2 vs. 2.8 days, p = 0.002) LOS were significantly reduced after EVAR compared to open repair. Hospital LOS was significantly lower after open retroperitoneal repair compared to transperitoneal repair (6.1 vs. 10.3 days, p = 0.001). Thirty-five patients (13%) underwent ruptured AAA-R, with only 34.3% mortality (in-hospital and 30-day). Forty-one patients (15%) underwent repair of complex aortic aneurysms, with 14.1% mortality. There are increasing societal and economic pressures to direct patient referrals to "centers of excellence" for specific surgical procedures. Although our institution meets neither of the Leapfrog Group's proposed criteria, our mortality and LOS for both intact and ruptured infrarenal AAA-R are equivalent or superior to published benchmarks for high-volume hospitals. Individual institutional outcome results such as these suggest that patient referral and care should be based upon actual, carefully verified outcome data rather than utilization of surrogate markers such as case volume and subspecialist involvement in postoperative care.