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External validation of a prognostic model for survival of patients with abdominal aortic aneurysms

External Validation of a Prognostic Model for Survival of Patients With Abdominal Aortic Aneurysms Treated by Endovascular Aneurysm Repair.

Eur J Vasc Endovasc Surg. 2024 May;67(5):718-725. Dabravolskaité V, Aweys MM, Venermo M, Hakovirta H, Mufty H, Zimmermann A, Makaloski V, Meuli L. Epub 2023 Nov 22. PMID: 37995960. https://www.ejves.com/article/S1078-5884

Objective

  • Current guidelines recommend monitoring the diameter of small and asymptomatic abdominal aortic aneurysms (AAA) due to the low risk of rupture.
  • Elective AAA repair is recommended for diameters ≥ 5.5 cm in men and ≥ 5.0 cm in women (or less depending on the DAP of the native aorta in women)
  • However, data supporting the effectiveness of elective treatment for all patients above these thresholds diverge. For a subgroup of patients, life expectancy could be very short and elective AAA repair at the current threshold may not be justified. This study aimed to externally validate a predictive survival model for patients with asymptomatic AAA treated by endovascular aneurysm repair (EVAR).

Methods This is an international multicentre retrospective observational cohort study. Data were collected from four European aortic centres treating patients between 2001 and 2021. The initial model included age, estimated glomerular filtration rate (eGFR) and chronic obstructive pulmonary disease (COPD) as independent predictors of survival. Model performance was measured by discrimination and calibration.

Results The validation cohort included 1,500 patients with a median follow-up of 65 months, during which 54.6% of patients died.

External validation showed slightly decreased discriminatory ability and signs of overfitting in model calibration. However, a high-risk subgroup of patients with impaired survival rates was identified:

  • octogenarians with eGFR < 60 or COPD,
  • septuagenarians with eGFR < 30
  • septuagenarians with eGFR < 60 and COPD with survival rates of only 55.2% and 15.5% at five and 10 years, respectively. The validated prognostic model identifies a high-risk subgroup of patients with asymptomatic abdominal aortic aneurysm (AAA) and a survival rate of only 16% at 10 years. The benefit of endovascular aneurysm repair in these patients must be questioned, provided the AAA does not carry a significant risk of rupture.

Conclusion EVAR is an interesting therapeutic option for AAA, particularly for patients who cannot benefit from open repair. Nevertheless, not all of these patients will benefit from EVAR, and an individualised treatment recommendation must take life expectancy into account. This study provides risk stratification to identify patients who may not benefit from EVAR using current diameter thresholds.

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