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Transcatheter Aortic Valve Leaflet Characteristics Influence Neo-Sinus Geometry And Leaflet Thrombosis Potential
Beatrice E. Ncho, Ph.D, Vahid Sadri, Ph.D, Andrew W. Siefert, Ph.D, Ajit P. Yoganathan, Ph.D.
Georgia Institute of Technology, ATLANTA, GA, USA.

OBJECTIVE: Leaflet thrombosis (LT) is a documented complication after transcatheter aortic valve replacement due to its possible influence on valve performance and durability. Although causes are not clearly defined, studies show the thrombus to be primary located around the bottom leaflet insertion of the valve. This region termed the 'neo-sinus' is unique, and studies report that its local flow characteristics provide understanding of flow stasis, which could exacerbate or diminish leaflet thrombosis. This study sought to investigate varied leaflet design characteristics and their effect on neo-sinus flow stasis.
METHODS: Eight custom transcatheter aortic valve (TAV) models of varied leaflet insertion heights (low - 0, mid - 7 and high 12 mm), leaflet length ( SL - 12 mm and LL - 15 mm) and leaflet material (BP- bovine and PP-porcine pericardium) were developed and tested in a pulsatile simulator. En-face high speed imaging and particle image velocimetry methods were used to quantify the leaflet kinematics and neo-sinus flow characteristics. Comparisons of pressure gradients, orifice areas, neo-sinus velocity fields and particle residence times (PRT) were made to investigate effects of design characteristics.
RESULTS: Porcine pericardium leaflet material (PP), shorter leaflet length (SL) and increased leaflet insertion height characteristics were observed to reduce transvalvular pressure gradients, increase effective orifice areas, and decrease valve opening times (Table 1). In addition, these leaflet characteristics demonstrated reduced neo-sinus geometry, increased velocities, and reduced PRTs corresponding to decreased flow stasis.
CONCLUSIONS: The outcomes from this study provide new insights to the potential implications of TAV selection given valve design contributes to minimizing flow stasis, and could reduce risk of leaflet thrombosis.

Table 1. Hydrodynamics, Leaflet Kinematics, Neo-sinus Geometry and Flow Results from 8 TAV models.
TAV IDTransvalvular pressure gradient (mmHg)Effective Orifice Area (cm2)Rapid valve opening time (ms)Estimated Neo-sinus volume (cm3)Neo-sinus peak velocity (m/s)Neo-sinus PRT (Cardiac cycles)
BP-Low-LL16 0.51.4 0.0366 4.21.490.0762.3
BP-Mid-LL16 0.41.4 0.0348 5.70.880.150.6
BP-High-LL15 0.11.8 0.0034 4.20.380.160.6
BP-Low-SL15 0.31.5 0.0053 2.71.120.121.8
BP-Mid-SL9.8 0.22.1 0.0149 8.20.870.150.6
PP-Low-LL16 0.11.5 0.0239 4.21.350.140.9
PP-Mid-LL9.8 0.51.9 0.0423 2.70.800.240.4
PP-High-LL10 0.12.2 0.0121 2.20.390.180.3


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