Customized aortic repair : an alternative approach to aortic aneurysm repair using injectable elastomer

Abstract

Despite the rise of EVAR as treatment concept for abdominal aortic aneurysms during the last two decades, this concept is not flawless. For only a selection of the aneurysms is treatable with the current EVAR grafts, due to unfavourable neck morphology and distal anatomy. Furthermore, many complications such as endoleaks do occur after EVAR, leading to stringent follow-up programs with many harmful imaging studies and a great number of secondary interventions. To overcome the anatomical limitations and potentially many of the procedure related complications, a novel treatment concept called Customized Aortic Repair (CAR) has been devised: a method of excluding the aortic aneurysm using endovascular techniques to inject a biocompatible elastomer into the aneurysm sac. The non-polymerised liquid elastomeric solution is used to fill the aneurysm sac around a balloon-catheter. After the in situ polymerisation and balloon deflation, an endoluminal mould with a patent lumen excludes the aneurysm sac. The potential of this treatment concept has been investigated in this thesis. Experiments described in this thesis taught us that filling the aneurysm sac with the elastomer in an in-vitro circulation model diminished wall movement and thereby wall-stress significantly, underlining the potential of the treatment concept. In the same circulation model, the elastomer was successfully used to exclude type II, III and IV endoleaks. Besides the several in-vitro experiments, the feasibility of the concept was tested in an in__vivo porcine experimental model (n=3). In these preliminary experiments, the aneurysms of all three pigs were successfully excluded with the elastomer. Dislodgement tests in a tensile testing machine showed that EVAR grafts (Excluder, Endurant and Anaconda), when inserted in a neck shorter then 15 mm, can be dislodged from a bovine artery sample easily. The largest force was needed to dislodge the Anaconda. When the area between the aneurysm model and the graft was filled with elastomer, the dislodgement force increased significantly with all grafts with 139-1016%. Filling the aneurysm sac with elastomer may prove to be a useful adjuvance to EVAR, diminishing the chance of graft dislodgement and type I endoleak. As the elastomer will be used endovascular, the direct contact with blood requires a low thrombogenicity of the elastomer to prevent occlusive thrombosis or embolization. The thrombogenicity of this new elastomer was tested in a validated ex- vivo model and compared to ePTFE to validate its feasibility in vivo. No significant difference in FPA production and platelet activation was observed between elastomer and ePTFE grafts (p>0.05). By scanning electron microscopy, numerous platelet aggregates were observed on the ePTFE grafts whereas just a few adhered platelets and no aggregates were observed in the elastomer grafts. This thesis underlines the large potential of the CAR-treatment concept, but also discusses its limitations.