A Preclinical Model For Assessing Novel Bioabsorbable Polymers For Transcatheter Aortic Valve Replacement
Gregory Fontana1, Christophe Naz2, Susana Lopes2, Oleg Svanidze2, Martijn Cox2, Nicolas Borenstein3, Christian Spaulding4.
1Los Robles Hospital and Medical Center, Thousand Oaks, CA, USA, 2Xeltis, Eindhoven, Netherlands, 3IMM Recherche, Paris, France, 4Hopital Europeen Georges Pompidou, Paris, France.
OBJECTIVE: There is a clear trend for Transcathether Aortic Valve Replacement (TAVR) being performed in younger and lower risk patients. To sustain the current trend there is a need to develop alternative materials that can overcome the durability limitations of the animal tissue used in current TAVR devices. We have developed a preclinical model for the assessment of novel bioabsorbable polymer materials that allow formation of a new valve via Endogenous Tissue Restoration (ETR).
METHODS: An ovine model was chosen for its rapid calcification mechanism and modest growth, allowing long term follow-up to assess ETR. Delivery route was transapical as it provides easy access to the ovine aortic root. The bioabsorbable polymer materials were electrospun and mounted on a self-expandable nitinol frame. The frame included three feelers for clipping the native cusps, thus allowing adequate anchoring into the short ovine aortic root, as previously reported. A series of pilot implants (n=7) were performed to trigger further design modifications.
RESULTS: All pilot implantation procedures were successful. Modifications were made to improve subacute outcomes. Feelers were cushioned to avoid perforation of the native cusps. Due to the proximity of the aortic and mitral valves in the ovine model, cushioning of the inflow crowns was included to avoid damaging the mitral leaflets. After initial design optimization, over 50 implantations were performed with a procedural success rate of 96%. Acute performance showed none-to-trace regurgitation and peak pressures of 7.5±2.7mmHg. Chronic studies with 5 different bioabsorbable polymer materials with 3, 6 and 12 months follow-up are on-going.
CONCLUSIONS: The transapical ovine model is a reproducible and effective tool for assessing novel materials for TAVR. While there are challenges specific to the ovine anatomy, these can be overcome by modifying stent design and proper cushioning to avoid abrasion. Chronic studies with several novel bioabsorbable polymer materials are on-going. They could potentially be applied in combination with any commercially available frames and delivery systems including those designed for the transfemoral approach.
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