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Patients treated by surgeons who perform more open vascular operations of various types have better outcomes following open repair of an abdominal aortic aneurysm (AAA), researchers found.

The inhospital mortality rate was 9.8% with the lowest-volume open vascular surgeons and 4.8% with the highest-volume open vascular surgeons (P<0.0001), according to J. Gregory Modrall, MD, of the University of Arkansas for Medical Sciences in Little Rock, and colleagues.

A similar pattern was seen when only open AAA repair volume was considered (10.2% versus 4.5%, P<0.0001), the researchers reported in the December issue of the Journal of Vascular Surgery.

After multivariate adjustment, however, a surgeon's volume of several vascular operations remained a significant predictor of outcomes from open AAA repair, and the volume of open AAA repairs did not.

"Our data suggest that open skills may be less operation-specific than traditionally believed," the authors wrote. "It may be more important to be a skilled 'open' vascular surgeon with a robust experience, including a wide array of open vascular operations, than it is to be an expert aortic surgeon."

They said the finding "needs to be considered for future credentialing of surgeons."

Previous studies have shown an association between higher surgeon volume and improved clinical outcomes for several types of operations, including open AAA repair, which is assumed to be related to enhanced expertise, with contributions from better patient selection and perioperative management.

But it is unclear whether general surgeon volume or operation-specific volume is more important.

Modrall and colleagues explored the issue using data from the Nationwide Inpatient Sample on patients who underwent open repair of nonruptured AAAs from 2000 to 2008.

During the study period, there were an estimated 111,533 elective open AAA repairs performed nationally by 6,857 surgeons.

The average number of open AAA repairs performed by each surgeon each year was 2.4. The average number of a composite of open vascular operations -- including carotid endarterectomy, aortobifemoral bypass, femoral-popliteal bypass, and femoral-tibial bypass -- performed by each surgeon annually was 5.3.

After dividing the surgeons into deciles according to their surgical volume, the researchers found that the inhospital mortality rate from open AAA repair increased as volume decreased, for both overall volume and operation-specific volume.

Only overall volume remained a significant predictor of mortality, however, after adjustment for patient age, gender, race, elective repair, comorbidities, expected principal source of payment, and hospital teaching status and location (OR 0.994, 95% CI 0.992 to 0.996).

In an invited commentary, Timothy Kresowik, MD, of the University of Iowa in Iowa City, noted that considering surgical volume for credentialing or certification is problematic because the linear correlation between volume and patient outcomes is weak.

In addition, he wrote, "setting arbitrary minimum thresholds is potentially associated with a perverse incentive to try to meet the target number by doing more unnecessary procedures."

Nevertheless, he said that the finding that the overall surgical volume is a better predictor of outcomes than procedure-specific volume is the important take-home message.

"I would agree with the authors' conclusion that this suggests that overall experience with related types of procedures may be a better criteria for credentialing than a procedure-specific focus."

Modrall and colleagues acknowledged some limitations of the study, including its uncertain applicability to other vascular operations, the lack of information on endovascular therapies, which became the first-line treatment for AAAs during the study period, and the large number of patients who were excluded because they could not be linked to a specific surgeon.

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