Volume Standards for Open Abdominal Aortic Aneurysm Repair Are Not Associated With Improved Clinical Outcomes

Abstract

Background: Volume-outcome relationships exist for many complex surgical procedures, prompting institutions to adopt surgical volume standards for credentialing. The current Leapfrog Group Hospital volume standard for open abdominal aortic aneurysm repair (OAR) is 15 per year. However, this is primarily based on data from the 1990s and may not be appropriate given the dramatic decline in OAR. We sought to quantify the proportion of hospitals meeting volume standards, the difference in perioperative outcomes between low-volume and high-volume hospitals, and the potential travel burden of volume credentialing on patients.

Methods: We identified Medicare beneficiaries for individuals aged ≥65 years undergoing OAR in 2013-2014. Hospital "all-payer" annual volume was estimated based on the national proportion of patients undergoing OAR covered by Medicare in the Vascular Quality Initiative. Hospital annual OAR volume was characterized as <5/year, 5-9/year, 10-14/year, and ≥15/year (high volume). Adjusted rates of postoperative morbidity, reoperation, failure to rescue, and mortality in 2014 were compared across volume cohorts. Distance between patients' home zip code and high-volume hospitals was calculated.

Results: A total of 21,191 OARs were performed at 1,445 hospitals between 2013 and 2014. The average hospital OAR annual volume was 7.8 (standard deviation [SD] ± 9.3) with a median of 4.5. Among the 1,445 hospitals, only 190 (13.1%) performed ≥15 OARs per year whereas 756 hospitals (53.3%) performed <5 per year. Among patients who underwent OAR in 2014, 5,395 (53.3%) received care at a hospital that performed <15 per year. There was no difference in complication, reoperation, or failure to rescue rates between high-volume and low-volume hospitals. Mortality did not significantly differ among OAR volume cohorts. Hospitals performing <5 OARs per year had a mortality rate of 5.7% compared with 5.6% at high-volume hospitals (P = 0.817). One-quarter of patients who received care at a low-volume hospital would have had to travel more than 60 miles to reach a high-volume hospital.

Conclusions: By conservative estimates, only 13% of hospitals performing OAR meet current volume standards. Triaging all patients to high-volume hospitals would require shifting over 5,000 patients annually with no associated improvement in perioperative outcomes. Implementation of the current OAR hospital volume standard may significantly burden patients and hospitals without improving surgical outcomes.