Risk Stratification of Patients Being Considered for Open Abdominal Aortic Aneurysm Repair.

Background/Objectives: Endovascular repair (EVAR) is the default for most abdominal aortic aneurysms (AAAs), yet open repair (OR) remains necessary, and the decision hinges on fitness for open surgery. No standardized preoperative tool defines who is "unfit" for OR. We derived and validated a preoperative risk score for severe major adverse events (MAE) after elective OR and examined whether high-risk patients had fewer perioperative events with EVAR. Methods: Using the Vascular Quality Initiative (VQI) Open AAA registry, we identified 9833 elective AAA OR patients without prior aortic surgery. Severe MAE was a 30-day composite of death, myocardial infarction (MI), stroke, new dialysis, or bowel ischemia. A multivariable model was converted to an integer score, validated, and benchmarked against the Revised Cardiac Risk Index (RCRI), E-PASS, and a Vascular Quality Initiative Frailty Index. High-risk (score ≥ 7) OR patients were propensity score matched 1:1 to elective EVAR patients and outcomes were compared. Results: Severe MAE occurred in 10.8% of OR patients. The 0-18-point score had an optimism-corrected C-statistic of 0.67 and calibration slope of 0.96, and it outperformed RCRI (C 0.57), E-PASS (C 0.61), and a Vascular Quality Initiative Frailty Index (C 0.63) (all ΔAUC p < 0.001). Severe MAE rose across low (4%), intermediate (9%), and high (20%) tiers; performance was stable on temporal validation (AUC 0.67, slope 0.94). Among 2357 matched high-risk pairs, severe MAE was 20.3% (OR) vs. 4.4% (EVAR) (risk difference +15.9 percentage points; relative risk 4.6), with the largest absolute benefit in the highest-risk patients. Conclusions: A simple preoperative score stratifies perioperative risk for elective open AAA repair and outperforms generic indices. High-risk patients would have had markedly fewer perioperative adverse outcomes if treated with EVAR. These associational findings can inform shared decision-making.