Current European Society for Vascular Surgery (ESVS) guidelines endorse a minimum open AAA repair (OAAA) center volume of 20 procedures per year as a proxy for high-quality care. By contrast, the Society for Vascular Surgery (SVS) and LeapFrog Group espouse only 10 OAAA repairs per year. Accordingly, debate persists with real-world implications regarding surgeon credentialing and healthcare resource allocation. The purpose of this analysis was to determine which endorsed threshold better discriminates OAAA repair mortality.
All elective OAAA repairs from 2010-2020 in the Vascular Quality Initiative (VQI) were identified and center level outcome comparisons were made using ESVS (≥20) vs. SVS/Leapfrog (≥10) volume thresholds. The primary outcome was in-hospital mortality. Logistic regression was used for risk-adjusted comparisons.
A total of 8,761 OAAA repair procedures were performed at 193 centers across North America. Median annual center volume was 6.6 [IQR 3.3, 9.9] OAAAs per year. Overall, in-hospital mortality was 3.5% (n = 303). The proportion of centers meeting ESVS and SVS/Leapfrog volume thresholds was only 12% (n = 22) vs. 25% (n = 48), respectively. There was an absolute difference in observed mortality of 0.3% among centers performing ≥ 20 vs. ≥ 10 OAAA repairs per year (2.6% vs. 2.9%). There was a significant linear association between center volume and mortality; however, the effect between ESVS (≥ 20) vs. SVS/LeapFrog (≥10) was small (risk decreased 0.2% per procedure; OR multiplies by 0.98 for each unit increase in volume, 95%CI .97-.99; p = 0.0003) (Figure). Moreover, there was no difference in the risk-adjusted protective effect of treatment at centers with either ≥10 or ≥20 cases per year (≥10 vs. <10, OR = 0.66 (.49 - .88), p = 0.005; ≥ 20 vs. < 20, OR = 0.63 (.45 - .87), p = 0.005; p-value for comparison of ORs = 0.78). Lastly, there was no significant difference in the projected percentage of deaths avoided based upon center volume thresholds (≥ 20, 3.3% vs. ≥10, 3.4%).
It appears that the SVS/LeapFrog recommended OAAA repair volume threshold of ≥10 discriminates perioperative mortality as effectively as ESVS ≥20 procedures per year. Moreover, it should be emphasized that a majority of North American hospitals fail to meet either the ESVS or SVS/Leapfrog operative benchmarks, calling into question the utility of competing recommended center volume guidelines. Based on these findings, a volume alone approach may fail to optimize AAA outcomes. Rather, alternative processes to align care delivery with documented high-performing centers may better serve to enhance international AAA repair.