Derivation and validation of a practical risk score for prediction of mortality after open repair of ruptured abdominal aortic aneurysms in a U.S. regional cohort and comparison to existing scoring systems

Abstract

Objective Scoring systems for predicting mortality after repair of ruptured abdominal aortic aneurysms (RAAAs) have not been developed or tested in a United States population and may not be accurate in the endovascular era. Using prospectively collected data from the Vascular Study Group of New England (VSGNE), we developed a practical risk score for in-hospital mortality after open repair of RAAAs and compared its performance to that of the Glasgow aneurysm score, Hardman index, Vancouver score, and Edinburg ruptured aneurysm score. Methods Univariate analysis followed by multivariable analysis of patient, prehospital, anatomic, and procedural characteristics identified significant predictors of in-hospital mortality. Integer points were derived from the odds ratio (OR) for mortality based on each independent predictor in order to generate a VSGNE RAAA risk score, which was internally validated using bootstrapping methodology. Discrimination and calibration of all models were assessed by calculating the area under the receiver-operating characteristic curve (C-statistic) and applying the Hosmer-Lemeshow test. Results From 2003 to 2009, 242 patients underwent open repair of RAAAs at 10 centers. In-hospital mortality was 38% (n = 91). Independent predictors of mortality included age >76 years (OR, 5.3; 95% confidence interval [CI], 2.8–10.1), preoperative cardiac arrest (OR, 4.3; 95% CI, 1.6–12), loss of consciousness (OR, 2.6; 95% CI, 1.2–6), and suprarenal aortic clamp (OR, 2.4; 95% CI, 1.3–4.6). Patient stratification according to the VSGNE RAAA risk score (range, 0–6) accurately predicted mortality and identified those at low and high risk for death (8%, 25%, 37%, 60%, 80%, and 87% for scores of 0, 1, 2, 3, 4, and ≥5, respectively). Discrimination (C = .79) and calibration (χ2 = 1.96; P = .85) were excellent in the derivation and bootstrap samples and superior to that of existing scoring systems. The Glasgow aneurysm score, Hardman index, Vancouver score, and Edinburg ruptured aneurysm score correlated with mortality in the VSGNE cohort but failed to identify accurately patients with a risk of mortality >65%. Conclusions Existing scoring systems predict mortality after RAAA repair in this cohort but do not identify patients at highest risk. This parsimonious VSGNE RAAA risk score based on four variables readily assessed at the time of presentation allows accurate prediction of in-hospital mortality after open repair of RAAAs, including identification of those patients at highest risk for postoperative mortality.

Strategy of endovascular versus open repair for patients with clinical diagnosis of ruptured abdominal aortic aneurysm: the IMPROVE RCT

“…Previous risk scores have been derived but are generally based on in-hospital mortality as an outcome and are therefore sensitive to changes and improvement in critical care. 93 Furthermore, few of these risk scores have been validated externally. We therefore used the opportunity presented by the collection of individual patient data from the three largest ruptured AAA trials undertaken worldwide and two observational cohorts [ …”

“…We compared the developed IMPROVE risk scores with previously published risk scores, namely the Vascular Study Group of New England risk score, 93 the Hardman index 30 and the Vancouver risk score. 94 The derivation of each score is given in Appendix 2, Table 41.…”

Editor's Choice - External Validation of Models Predicting Survival After Ruptured Abdominal Aortic Aneurysm Repair

“…These results are in accordance with previous disappointing results on discrimination, 27 but in conflict with previous fairly accurate results on calibration. 23 Therefore, the accuracy of the Vancouver Figure 4. The calibration plots of the Vancouver score before and after recalibration.…”

“…These results are in conflict with one validation study with sufficiently accurate discrimination, 25 but in accordance with another validation study with insufficiently accurate discrimination. 23 Concerning calibration, one previous validation reported an observed death rate of 50% in patients with a predicted death rate of 80% (estimated from figure). 23 Because results regarding the ERAS are conflicting, the present authors question its precision.…”

“…23 Concerning calibration, one previous validation reported an observed death rate of 50% in patients with a predicted death rate of 80% (estimated from figure). 23 Because results regarding the ERAS are conflicting, the present authors question its precision.…”