IYSC08 - Aortic Biomechanics and Early Sac Regression After Endovascular Aneurysm Repair

Objectives: Early sac regression, within the first postoperative year, may act as a surrogate marker for success of Endovascular Aneurysm Repair (EVAR) and is associated with improved surgical outcomes as well as long-term survival. Little is known about the preoperative biomechanical landscape and its value for predicting outcome such as sac regression.

Methods: Between January 2009 and June 2012, all patients undergoing bifurcated EVAR for Abdominal Aortic Aneurysm at the Vascular Surgery Department of Karolinska University Hospital were considered for inclusion in this retrospective observational cohort study. Finite element analysis was performed on all preoperative CTAs using A4 Clinics, yielding biomechanical variables such as AAA wall strength and wall stress ratio as well as Intra-Luminal Thrombus (ILT) thickness and ILT stress. The preoperative, 30-day and 1-year CTAs were reviewed for measurement of maximal AAA diameter (dMax) and volume, using 3Mensio Vascular. Sac regression, was defined as ≥5mm maximal diameter decrease between the first and second postoperative follow-up CTA. Multivariable linear regression modeling constituted analysis for risk factors of sac change.

Results: Sixty-four patients were included. Thirty-nine (61%) out of the sixty-four patients included presented with sac regression. Twenty-five had a stable sac or sac increase. No significant difference in demographics was seen between the groups; mean age was 73 vs 76 years, male sex 85% vs 96% and median AAA diameter was 58mm vs 58.5mm, respectively. Univariable analysis of preoperative biomechanical characteristics were similar between cases with and without sac regression. The multivariable linear regression however, revealed several variables affecting sac regression. Max ILT-stress β (Beta) 0.25 (95%CI 0.02 – 0.48, p = 0.035), ILT-thickness β 0.25 (95%CI 0.05 – 0.45, p = 0.012), age β 0.31 (95%CI 0.06 – 0.56, p = 0.016) and use of aspirin β 4.42 (95%CI 0.28 – 8.57, p = 0.037), significantly decreased sac regression whilst dMax at 1 month postoperatively β -0.50 (95%CI -0.83 – (-0.16), p = 0.004) and current or former smoking status β -5.41 (95%CI -10.6 – (-0.18), p = 0.43) positively influenced sac change within the first postoperative year. Cases with sac regression had fewer reinterventions (log rank p = 0.006) and lower 5-year mortality (log rank p = 0.009).

Conclusions: This pilot study, showed an association between preoperative maximal ILT stress and ILT thickness with sac change after EVAR. A majority of the study cohort responded well to EVAR and demonstrated early sac regression including less reinterventions and lower mortality.