Higher-volume hospitals have lower mortality rates after open repairs of complex abdominal aortic aneurysms (AAAs). However, the clinical mechanisms underlying this association remain elusive. We assessed whether rates of postoperative complications versus failure to rescue (defined as death after a major postoperative complication) better explained lower mortality rates among higher-volume hospitals after open repairs of complex AAAs. Using the 2004 to 2018 Vascular Quality Initiative, we identified all patients who underwent open repairs of complex AAAs, where the proximal clamp site was above at least one renal artery. After dividing patients into quintiles by annual hospital volume, we compared risk-adjusted rates of 30-day postoperative mortality, complications, and failure to rescue between the lowest volume and highest volume hospitals. Multivariable logistic regressions adjusted for clinical and intraoperative factors (ie, proximal clamp site, ischemia time, iliac aneurysmal disease), and hospital clustering. We identified 3566 patients (median age, 71 years; 81% male; 92% Caucasian; median aneurysm size, 5.9 cm) undergoing open repairs of complex AAAs. The risk-adjusted mortality rate was 2.5 times greater among lower volume hospitals relative to higher volume hospitals (7.4% vs 3.0%; P < .01). While risk-adjusted complication rates were respectively similar (29.5% vs 26.9%; P = .06), risk-adjusted failure-to-rescue rates were 2.3 times greater among lower volume hospitals relative to their higher volume counterparts (6.3% vs 2.7%; P = .02) (Table). The most common postoperative complications included renal dysfunction (25%), cardiac dysrhythmia (14%), and pneumonia (14%), with their specific rates of failure to rescue varying from 12% to 22%. Higher volume hospitals have lower mortality rates after open repairs of complex AAAs because they better “rescue” patients from complications, relative to their lower volume counterparts. Understanding the clinical mechanisms underlying this association, from macroscopic hospital factors to communication and culture, in addition to the regionalization of open repairs of complex AAAs, may improve patient outcomes.TableMultivariate logistic regressions assessing the association between hospital volume and all three outcomesHigh-volume hospitalsLow-volume hospitalsaOR (95%-CI)aP valueaMortality3.0%7.4%2.51 (1.42-4.42)<.01Complications27.1%29.2%1.31 (0.91-1.90)0.15Failure-to-rescue2.7%6.3%2.30 (1.16-4.57)0.02aAdjusted for hospital volume quintiles, patient age, gender, race, insurance, BMI, smoking history, aneurysm diameter, operative approach, intraoperative ischemia time, prior aortic surgery, presence of iliac aneurysms, comorbidities (COPD, CKD, heart disease, DM, PVD, carotid artery stenosis or endarterectomy) and hospital-level clustering. Reference: high-volume hospitals. Open table in a new tab