Effect of Surgeon and Hospital Volume on Mortality After Aortic Aneurysm Repair
Are surgeon and hospital procedure volumes associated with mortality following endovascular (EVAR) or open repair of abdominal aortic aneurysms (AAAs)?
Medicare beneficiaries who underwent AAA repair from 2001-2008 were analyzed. Surgeon and hospital volumes were measured over the year preceding each procedure and categorized into quintiles. Multilevel logistic regression models evaluated effects of surgeon volume, adjusting for hospital volume, on mortality.
122,495 AAA repairs (77,044 EVAR and 45,451 open) were studied. Hospital volume, but not surgical volume, was associated with mortality after EVAR (1.9% for hospital quintile 1 [0-9 EVARs] vs. 1.4% for quintile 5 [49-198 EVARs]; p < 0.01). After open AAA repair, perioperative mortality decreased with higher surgeon volume (6.4% for quintile 1 [0-3 open repairs] vs. 3.8% for quintile 5 [14-62 open repairs; p < 0.01] and hospital volume (6.3% for quintile 1 [0-5 open repairs] vs. 3.8% for quintile 5 [14-62 open repairs]; p < 0.01).
Perioperative mortality after open AAA repair is associated with both surgeon and hospital volume. In contrast, only a weak association with hospital volume (and no association with surgeon volume) was observed for mortality after EVAR. The authors concluded that open aortic surgery should be concentrated in high-volume hospitals and surgeons.
The quintile cut-points from this analysis are every bit as important as the model findings and conclusions, which suggest that lower perioperative mortality could be achieved through concentration of open AAA repair at high-volume centers. Defining ‘high volume’ would affect access and provider availability, while reduction of open repair volume at ‘mid-volume’ centers would potentially affect ability to offer open repair for symptomatic or ruptured AAA (where patient transfer may be unsafe) as experience diminishes. Although the authors allude to mortality reductions observed in the United Kingdom through similar approaches in the discussion, differences in health systems and scale might make implementation in the United States more complex, particularly if the redistribution of volume leads to delays in repair. Concentration of open repairs at high-volume centers would also concentrate training in open surgical repair, potentially reducing the pool of surgeons able to offer this technique. Lack of anatomic data is a major limitation of this study and prevented adjustment for aneurysm diameter, extent, and other factors related to risk and selection.
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