Surgeon Case Volume, Not Institution Case Volume, Is the Primary Determinant of In-Hospital Mortality After Elective Open Abdominal Aortic Aneurysm Repair
What are the relative effects of hospital and surgeon volume on outcomes after both endovascular (EVAR) and open repair of intact elective abdominal aortic aneurysms (AAAs)?
All patients undergoing repair of elective, intact AAAs in the Nationwide Inpatient Sample (NIS) from 2003-2007 were identified. Data from 11 participating states that use a physician identifier for each procedure were included. Surgeon and hospital annual volumes for EVAR and open AAA repair were determined and placed in quintiles. Multivariate models were utilized to evaluate the association of institution and surgeon volume with in-hospital mortality for EVAR and open AAA repair.
A total of 5,972 open AAAs and 8,121 EVARs were identified in the NIS over the study period. For open AAA repair, patients in high-volume hospitals as well as those operated on by high-volume surgeons experienced a significant mortality reduction. High surgeon volume conferred a greater reduction in mortality than did hospital volume. The lowest mortality was seen in high-volume surgeons despite institutional volume (8.7%, 3.6%, and 0%; p < 0.001 for low-, medium-, and high-volume surgeons at low-volume institutions and 6.7%, 4.8%, and 3.3%; p = 0.020 at medium-volume institutions). High-volume hospitals showed a similar trend, with mortality rates of 5.1%, 3.4%, and 2.8% for low-, medium-, and high-volume surgeons (p = 0.57). Multivariate analysis demonstrated that low surgeon volume independently predicted mortality (odds ratio, 2.0), whereas low-volume hospitals did not. For EVAR, neither institutional nor surgeon volume influenced outcome.
The authors concluded that for open AAA repair, there appears to be an association between in-hospital mortality and surgeon case volume, but not hospital volume. No such relationship appears to exist for EVAR.
In an age of ‘selective referral practices,’ groups such as the Leapfrog group have been at the forefront of grading hospitals for surgical treatment of diseases such as AAAs. Hospital volume figures significantly in determination of these hospital rankings. This study suggests that surgeon volume, rather than hospital volume, is the major determiner of in-hospital mortality rather than hospital volume. This is interesting in that patients intuitively grasp this fact. Patients routinely ask me how many open AAA repairs or EVARs I perform each year. I have never been asked how many my institution performs. Determining a relationship between surgeon volume and EVAR will remain difficult, as the mortality associated with EVAR is very low. Regardless, thoughtful and accurate processes for hospital ranking for open AAA repair and EVAR are mandatory.
Keywords: Hospitals, Surgical Procedures, Elective, Hospital Mortality, Aortic Aneurysm, Abdominal, Vascular Surgical Procedures
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