Volume-Outcome Relationships and Abdominal Aortic Aneurysm Repair

Abstract

Conclusion: There is a steady increase in perioperative survival for abdominal aortic aneurysm (AAA) repair with increasing volume of open repair, but beyond a low threshold, there is little improvement in survival with increasing volume of endovascular AAA repair. Summary: For higher-risk procedures, higher-volume institutions and higher-volume operators achieve better results. Infrarenal AAA may be repaired with open or endovascular techniques. Surgeons who favor one approach over the other may have outcomes for the opposite approach that are not as good as their favored approach. Outcomes across procedures may not be related. The authors note that to date, there have been no studies examining volume outcome relationship of AAA that take in to consideration endovascular vs open AAA repair. The authors used Medicare data to investigate if there was a relationship between institutional volume for endovascular and open AAA repair and outcome. They used this information to extrapolate potential implications for physicians referring patients for AAA repair. Data was from the period of 2001 to 2006 and was used to trend institutional volume. Outcomes were assessed with a previously assembled propensity score-matched cohort from 2001 to 2004. Medicare beneficiaries underwent 230,736 repairs of intact or ruptured AAA from 2001 to 2006. Endovascular repairs increased as a percentage of the total from 22% in 2001 to >50% in 2006. There was only a minimal shift in procedure volume to higher-volume institutions. Adjusted mortality by quintiles showed a marked decrease between the first and second quintile for endovascular repair, with only smaller decreases over quintiles 3 to 5. For open repair, adjusted mortality showed a steady decrease across the quintiles. The number of high-volume open repair hospitals decreased over time. In 2001, there were 110 high-volume open repair hospitals. with approximately 25% of repairs in these hospitals being endovascular. In 2006, only 31 hospitals were considered high-volume for open repairs, and 43% of aortic aneurysm repairs in these hospitals were endovascular. Almost 400 hospitals stopped performing open repair during the study period. Comment: The data indicate that the number of hospitals with a high volume of open AAA repair has declined dramatically. In addition, almost 400 hospitals stopped performing any open AAA repairs in the endovascular era! The data seem to justify this trend. For endovascular repair, mortality improvement occurs really only from lowest quintile to the second lowest quintile, with little improvement beyond that for increasing volumes of endovascular repair, perhaps justifying industry marketing of endovascular aortic grafts to low-volume hospitals and low-volume surgeons. On the other hand, there appears to be a relatively constant relationship between increasing open repair volumes of AAA repair and decreasing perioperative mortality after open AAA repair. Given that referring physicians frequently do not know whether a patient will undergo open or endovascular AAA repair, the authors suggest referral decisions should be made on the basis open AAA repair volume of a hospital rather than the total or endovascular repair volume. What is clear is that as endovascular repair continues to increase, there are going to be fewer hospitals with adequate open repair volume to achieve optimal results with open AAA repair.