IYSC08 - Factors affecting sac regression after embolization with Shape Memory Polymer Plugs in patients with EVAR.

Objectives: EVAR is increasingly used for treatment of infrarenal abdominal aortic aneurysm with improved short-term outcomes compared to open abdominal aortic aneurysm repair. However, these results are balanced by the increased need for surveillance and re-intervention in patients undergoing endovascular repair, often in the context of sac growth due to endoleak. Methods for intra-operative prevention of endoleak include a novel method of sac embolization using shape memory polymer plugs which are comprised of a porous, bioabsorable polyurethane scaffold to induce thrombosis of the aneurysm sac, cellular infiltration and tissue ingrowth. The investigational use of shape memory polymer devices for aneurysm sac management has been reported in early feasibility studies. This is the first real-world, global multicenter report to date.

Methods: A multicenter, retrospective, two-arm CTA analysis of sac volume regression was performed on 97 patients. 56 patients were treated with EVAR plus prophylactic sac management (EVAR-PSM) using shape memory polymer between 2019 and 2022, including 31 patients treated prospectively at five centers from New Zealand and the Netherlands in the AAA-SHAPE early feasibility studies (NCT04227054, NCT04751578), and 25 patients treated at nine centers from the US and Europe in a real-world setting. Forty one patients were treated with standard EVAR at a single center between 2014 and 2019, matched to the same inclusion criteria as AAA-SHAPE. Analysis of sac volume regression as a function of pre-operative thrombus burden and number of patent accessory vessels was performed for all groups, and aneurysm packing density and average plug distance from accessory vessels for EVAR PSM only was performed at baseline (30 days) and one-year follow-up.

Results: 97 patients with EVAR-PSM and 41 control patients were identified. The presence of preoperative thrombus was found to be significantly associated with sac regression in the control group (p <.02) but not in the treatment group (p>.05) (Figure 1). In the EVAR-PSM group, average plug distance from accessory vessels was found to be significantly associated with sac expansion, both on simple regression (p <.01) and on multivariate analysis (p <.01). Chi-squared analysis demonstrated patients in the EVAR-PSM group to have higher rates of sac volume regression of greater than 10% compared to the control group (Figure 2).

Conclusions: In EVAR, thrombus may play a role in preventing type II endoleak and sac expansion from accessory vessels. Shape memory polymer may play a similar role to thrombus and promote sac regression, but require careful plug deployment near accessory vessels.