A new study in the March 2011 issue of the Journal of Vascular Surgery has revealed that for open repair of intact elective abdominal aortic aneurysms, surgeon annual volume rather than institutional volume is more strongly associated with decreased in-hospital mortality.
Previous studies have primarily centered on institutional volume rather than individual surgeon volume; therefore researchers wanted to statistically determine the relative effects of both in-hospital mortality after open and endovascular aneurysm repairs (EVAR) for abdominal aortic aneurysms.
Co-author Andres Schanzer, a surgeon from the division of vascular and endovascular surgery at the University of Massachusetts Medical School in Worcester, said that the Nationwide Inpatient Sample (2003-2007) was used to identify all patients who underwent open repair (5,972) or EVAR (1,821) for non-ruptured abdominal aortic aneurysms in 11 participating states that record a unique physician identifier for each procedure were reviewed.
Surgeon and institution volume were defined as low (first quintile), medium (second, third, or fourth quintile), and high (fifth quintile). Stratification by institution volume and then by surgeon volume was performed to analyse in-hospital mortality. Multivariable models were used to evaluate the association of institution and surgeon volume with mortality for open repair and EVAR, controlling for potential confounders.
Schanzer said that for open abdominal aortic aneurysm repair, a significant mortality reduction was associated with both annual institution volume (low less than 7, medium 7-30, and high less than 30) and surgeon volume (low less than 2, medium 3-9, and high more than 9). He added that high surgeon volume conferred a greater mortality reduction than did high institution volume.
When low and medium volume institutions were stratified by surgeon volume, mortality after open abdominal aortic aneurysms repair was inversely proportional to surgeon volume (8.7%, 3.6 %, and 0% for low, medium, and high-volume surgeons at low-volume institutions; and 6.7%, 4.8%, and 3.3% for low, medium, and high-volume surgeons at medium-volume institutions). High-volume institutions stratified by surgeon volume demonstrated the same trend (5.1%, 3.4%, and 2.8%) however this finding was not statistically significant.
“We believe that it is a shortcoming of publicly reported data and volume-based studies to consider EVAR and open abdominal aortic aneurysms repair together, as it can be misleading,” added Schanzer. “For example, from an open surgical perspective, it is inappropriate to categorise a centre as a high volume abdominal aortic aneurysms institution based on the fact that they perform 50 EVAR’s per year and 5 open abdominal aortic aneurysms repairs per year. The reverse also is true, from an EVAR perspective, at a centre that performs 50 open abdominal aortic aneurysms repairs per year and 5 EVARs per year.”
Researchers added that their data indicated that a strategy of open aneurysm repair regionalisation that is based solely on institution volume is misguided; in contrast, elective EVAR of intact abdominal aortic aneurysms show universally low mortality rates (2% or less) can be expected regardless of surgeon or hospital experience.
“Regionalisation of abdominal aortic aneurysms should focus on open repair because EVAR outcomes are equivalent across volume levels and payers may need to re-evaluate strategies that encourage open abdominal aortic aneurysm repair at high-volume institutions if specific surgeon volume is not considered,” concluded Schanzer.