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Structural Analysis of Stenotic Aortic Valves: Application to Percutaneous Aortic Valve Implantation

Hoda Maleki1, Shahrokh Shahriairi1, Michel Labrosse2, Louis-Gilles Durand3, Lyes Kadem1.
1Concordia University, Montreal, QC, Canada, 2University of Ottawa, Ottawa, ON, Canada, 3Institut de Recherches Cliniques de Montreal, Montreal, QC, Canada.


Structural Analysis of Stenotic Aortic Valves: Application to Percutaneous Aortic Valve Implantation
Objectives: Percutaneous aortic valves (PAVs) allow valve replacement without open chest surgery in patients with elevated surgical risks. The promising clinical results obtained using this technique encourages its application to a larger population and mainly younger patients. However, such population is characterized by more calcified leaflets and significantly higher aortic valve mass. PAV replacement might, therefore, fail or be sub-optimal under such conditions. It is then important to develop parameters that can characterize noninvasively the properties of the native calcified aortic valve prior to PAV valve replacement. Our hypothesis is that this can be achieved through a combination clinical data (geometrical orifice area (GOA) and pressure waveforms) and numerical simulations of the native calcified aortic valve.
Methods: A finite element model (FEM) of the aortic valve and the ascending aorta has been developed. Aortic valve material properties were simulated as hyperelastic, nonlinear and anisotropic. GOA and aorta and left ventricular pressure waveforms have been determined in vitro using two validated silicone models of aortic stenosis (AS) with GOAs of 1.4 cm2 (moderate AS) and 0.94 cm2 (severe AS). Our algorithm consisted of modifying the material properties of the FEM aortic valve until the numerical GOA corresponds to the in vitro GOA under the same pressure conditions.
Results: Our results show:
• Stenotic aortic valve material properties can be characterized by modifying only one parameter (C1) of the material properties. The material properties of the moderate and severe models of AS tested in vitro correspond then to values of C1 of 0.95 and 3.25 MPa, respectively.
• Our model was capable of correctly reproducing the opening and closure of silicone AS models (see Fig.1).
• Aortic regurgitation, a common occurrence in patients with AS, was also obtained numerically.
Conclusion: This combined numerical and experimental work allowed the development of an algorithm allowing the estimation of stenotic valve stiffness before implanting a percutaneous heart valve.
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