Original Article In-Vitro Assessment of the Effects of Transcatheter Aortic Valve Leaflet Design on Neo-Sinus Geometry and Flow BEATRICE NCHO, 1 VAHID SADRI, 2 JILLIAN ORTNER, 2 SAI KOLLAPANENI, 2 and AJIT YOGANATHAN 1,2 1 School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, USA; and 2 The Wallace H. Coulter School of Biomedical Engineering, Georgia Institute of Technology and Emory University, Technology Enterprise Park, 387 Technology Circle NW, Suite 200, Atlanta, GA 30313-2412, USA (Received 28 May 2020; accepted 16 October 2020) Associate Editor Umberto Morbiducci oversaw the review of this article. Abstract—Transcatheter aortic valve (TAV) leaflet throm- bosis is a clinical risk with potentially fatal consequences. Studies have identified neo-sinus flow stasis as a cause of leaflet thrombosis. Flow stasis is influenced by the TAV leaflets, which affect the local fluid dynamics in the aortic sinus and neo-sinus. This study evaluated the effects of TAV leaflet features on the neo-sinus flow as a measure of leaflet thrombosis risk. Five TAVs of varied leaflet length and insertion height were tested in a simulator. Hydrodynamics and leaflet kinematics through en-phase imaging were quan- tified. Velocity fields were assessed using high-speed particle image velocimetry. Regions of flow stasis and particle residence times (PRTs) were quantified. TAVs with shorter leaflet length exhibited larger orifice areas and lower transvalvular pressure gradients. Shorter leaflet length and increased leaflet insertion TAVs additionally exhibited lower neo-sinus PRTs (0.44 ± 0.21 vs 2.83 ± 0.48 cycles, p < 0.05) and higher neo-sinus peak velocities (0.15 ± 0.009 vs 0.07 ± 0.005 m/s, p < 0.05) than TAVs with longer leaflet length and lower leaflet insertion. The average neo-sinus volume positively correlated with PRT(r = 0.810, p < 0.001), and extent of flow stasis (r = 0.682, p < 0.05). These results suggest that a small neo-sinus volume may reduce flow stagnation and particle residence, potentially reducing the risk of leaflet thrombosis. We propose that leaflet design features might be proactively controlled in the design of future transcatheter aortic valves. Keywords—TAVR, Leaflet thrombosis, Neo-sinus, Leaflet length, Leaflet insertion height, Flow stasis, Leaflet kinemat- ics, Particle image velocimetry. ABBREVIATION 2D Two-dimensional LL Longer leaflet length LT Leaflet thrombosis PIV Particle image velocimetry PRT Particle residence time ROI Region of interest SL Shorter leaflet length STJ Sinotubular junction TAV Transcatheter aortic valve TAVR Transcatheter aortic valve replacement INTRODUCTION Transcatheter aortic valve replacement (TAVR) is a minimally invasive treatment for patients with severe degenerative calcific aortic stenosis. 3,12 In the past decade, this technique was primarily reserved for patients with intermediate to high surgical risk, then recently the Food and Drug Administration expanded indications of TAVR for low risk patients. 6 Short-term patient follow-up reports have indicated occurrence of several complications including leaflet thrombosis 15,20 even in low-risk patient populations 1 . Leaflet throm- bosis has been identified to be a deleterious complica- tion resulting in potentially fatal consequences. 23 Leaflet thrombosis (LT) is characterized by throm- bus covering the aortic side of a transcatheter aortic valve (TAV) leaflets. The presence of thrombus on the leaflets can reduce leaflet motion, impede forward flow, elevate the transvalvular pressure gradient, increase the load on the left ventricle; and possibly lead to heart failure, embolization, stroke and death. 4,5,9,30 Recent studies suggested that the hemodynamic environment surrounding the TAV is critical in the development of leaflet thrombosis. 19,28,29 This is because upon TAV Annals of Biomedical Engineering (Ó 2020) https://doi.org/10.1007/s10439-020-02664-0 BIOMEDICAL ENGINEERING SOCIETY Ó 2020 Biomedical Engineering Society