gms | German Medical Science

Background: Sac regression after Endovascular Aneurysm Repair (EVAR) of Abdominal Aortic Aneurysms (AAA) has been proposed as a marker of successful response to treatment. Several variables related to AAA morphology are reported to influence sac behavior post-EVAR yet little is known about the pre-operative biomechanical landscape and its value for predicting outcome such as sac regression.

Methods: Patients treated with EVAR for infrarenal AAA at the Karolinska University Hospital between 2009–2012 with one pre- and two post-operative computed tomography angiography (CTA) scans were considered for inclusion in this single-center retrospective cohort study. Biomechanical indices such as AAA wall strength and wall stress ratio as well as Intra-Luminal Thrombus (ILT) thickness and ILT stress were measured at preoperative CTAs A4Clinic (VASCOPS). AAA diameter and volume were analyzed on preoperative, 30-day and 1-year CTAs. Patients were dichotomized according to presence of sac regression, defined as ≥5mm decrease in maximal AAA diameter between the first two postoperative CTA scans. Multivariable linear regression modeling constituted analysis for risk factors of sac change. Sac regression status was correlated to rate of reintervention and survival at 5 years post EVAR.

Results: Of the 101 patients treated during the study period, 64 were included. Thirty-nine patients (61%) demonstrated sac regression compared with 25 cases (39%) with stable sac or sac increase. Mean age (73 vs 76 years), male sex (85% vs 96%) and median AAA diameter (58mm vs 58.5mm) did not differ significantly between patients with and without sac regression, respectively. Although no difference in preoperative biomechanics was seen between the groups, multivariable linear regression revealed several variables affecting sac regression. Age β (Beta) 0.31 (95%CI 0.06 – 0.56, p = 0.016), use of aspirin β 4.42 (95%CI 0.28 – 8.57, p = 0.037), Max ILT-stress β 0.25 (95%CI 0.02 – 0.48, p = 0.035) and ILT-thickness β 0.25 (95%CI 0.05 – 0.45, p = 0.012) 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. Sac regression was furthermore associated with fewer reinterventions (log rank p = 0.006) and lower mortality (log rank p = 0.009) at 5-year follow-up.

Conclusion: This pilot study, characterizing the biomechanical landscape in patients with and without sac regression demonstrated an association between preoperative measured maximal ILT stress and ILT thickness with a change in sac diameter after EVAR. Our study supports the notion that early sac regression is associated with less reinterventions and lower mortality after EVAR.

Competing interests: Professor Christian T. Gasser acts as scientific advisor to A4 Clinics 5.0 (VASCOPS, GmbH, Graz, Austria).