Hospital Volume and Long-Term Survival Among Medicare Beneficiaries Undergoing Surgical Repair of Acute Type A Aortic Dissection

Abstract

Despite guideline recommendations, transfer rates to high-volume aortic centers (high-VACs) for acute type A aortic dissections (TAAD) remain suboptimal. This may be because the benefit of undergoing surgical repair of TAAD at high-VACs remains poorly quantified. Medicare beneficiaries undergoing surgical repair of TAAD from 1999-2019 were identified. Hospital and surgeon annual aortic case volumes in Medicare beneficiaries were determined. Long-term survival after surgical repair of TAAD at low-volume aortic centers (low-VACs; <6 annual aortic cases), intermediate-volume aortic centers (intermediate-VACs; 6-27 annual aortic cases), and high-VACs (>27 annual aortic cases) was compared. Overlap propensity score weighting adjusted for measured confounding variables. 15,375 Medicare beneficiaries underwent surgical repair of TAAD from 1999-2019: 4119 (26.8%) at low-VACs, 7193 (46.8%) at intermediate-VACs, and 4063 (26.4%) at high-VACs. Over the study duration, the percentage of patients transferred from an outside medical facility for TAAD increased from 33% in 1999 to 50% in 2019 (Cochran-Armitage p<0.001). Transferred patients comprised 19% of cases performed at low-VACs, 43% at intermediate-VACs, and 64% at high-VACs. Risk-adjusted median survival at high-VACs was 6.6[6.3-7.1] years compared to 4.1[3.6-4.6] years at low-VACs, an advantage of 2.5[1.8-3.0] years. Risk-adjusted median survival at high-VACs was 6.7[6.4-7.1] years compared to 5.2[4.9-5.5] years at intermediate-VACs, an advantage of 1.5[0.9-1.9] years. Survival after surgical repair of TAAD is substantially improved at high-VACs compared to both low-VACs and intermediate-VACs. Although the prevalence of transfer for TAAD has increased since 1999, policy measures aimed at improving transfer rates have the potential to further enhance outcomes in TAAD.