Optimization and Verification of a Novel Trileaflet Polymeric Prosthetic Heart Valve
Claiborne, III, Thomas Edward
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Valvular heart disease remains a significant public health issue with Calcific Aortic Valve Disease (CAVD) its most life threatening form. Current treatment for CAVD involves open-heart surgical replacement of the diseased aortic valve (AV) with either a tissue (THV) or mechanical (MHV) prosthesis, with THVs being mostly nonthrombogenic but vulnerable to structural valve deterioration (SVD) and MHVs being highly durable but thrombogenic, thus requiring lifelong anticoagulant therapy. Alternatively, recently approved transcatheter aortic valve replacement (TAVR) is now available for inoperable patients with severe aortic stenosis. TAVR currently utilizes balloon- or self-expandable THVs. Polymeric valves (PHV) promise to avoid SVD and anticoagulants by using new biostable polymers and mimicking the native AV form and function. PHVs may be better suited for TAVR, where the valve experiences potentially damaging loads during crimping and deployment, and in devices such the Total Artificial Heart, which currently utilizes MHVs. We present the development of a novel PHV using a new thermoset polyolefin, xSIBS, and the completion of one optimization cycle using our Device Thrombogenicity Emulation (DTE) methodology, the goal of which is to reduce or eliminate the need for anticoagulants by employing a combination of numerical and experimental methods to optimize device designs, including finite element analysis, fluid-structure interaction, two-phase computational fluid dynamics (CFD), computer aided design, in vitro human platelet activation state (PAS) measurements, and hydrodynamics verification testing. Key features of the PHV were altered to optimized hemodynamics, and computer numerical control machined compression molding was used to create precision valve prototypes. The optimized PHV showed reduced stress concentrations in the leaflets under diastolic pressure loads, CFD produced favorable Thrombogenic Footprints, with stress loading waveforms extracted from regions of interest and emulated in our Hemodynamic Shearing Device showing significantly lower PAS in the optimized PHV. Prototype hydrodynamics were comparable to a gold-standard THV. This work has moved PHVs closer to clinical viability.