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Simplified multi-stage computational approach to assess the fatigue behavior of a NiTi transcatheter aortic valve during in vitro tests: a proof-of-concept study.

[+] Author and Article Information
Lorenza Petrini

Department of Civil and Environmental Engineering, Politecnico di Milano, Italy
lorenza.petrini@polimi.it

Elena Dordoni

Laboratory of Biological Structure Mechanics, Department of Chemistry, Materials and Chemical Engineering 'Giulio Natta', Politecnico di Milano, Italy
elena.dordoni@hotmail.it

Dario Allegretti

Laboratory of Biological Structure Mechanics, Department of Chemistry, Materials and Chemical Engineering 'Giulio Natta', Politecnico di Milano, Italy
dario.allegretti@polimi.it

Desiree Pott

Department of Cardiovascular Engineering, Institute of Applied Medical Engineering - Helmholtz Institute - RWTH Aachen University, Aachen, Germany
pott@ame.rwth-aachen.de

Maximilian Kütting

Department of Cardiovascular Engineering, Institute of Applied Medical Engineering - Helmholtz Institute - RWTH Aachen University, Aachen, Germany
max@kuetting.de

Francesco Migliavacca

Laboratory of Biological Structure Mechanics, Department of Chemistry, Materials and Chemical Engineering 'Giulio Natta', Politecnico di Milano, Italy
francesco.migliavacca@polimi.it

Giancarlo Pennati

Laboratory of Biological Structure Mechanics, Department of Chemistry, Materials and Chemical Engineering 'Giulio Natta', Politecnico di Milano, Italy
giancarlo.pennati@polimi.it

1Corresponding author.

ASME doi:10.1115/1.4035791 History: Received July 29, 2016; Revised January 09, 2017

Abstract

Nowadays, transcatheter aortic valve (TAV) replacement is an alternative to surgical therapy in selected high risk patients for the treatment of aortic stenosis. However, left ventricular contraction determines a severe cyclic loading for the implanted stent-frame, undermining its long-term durability. Technical standards indicate in vitro tests as a suitable approach for the assessment of TAV fatigue behavior: generally, they do not specify test methods but require to test TAV in the worst loading conditions. The most critical conditions could be different according to the specific valve design, hence the compartment where deploying the valve has to be properly identified. A fast and reliable computational methodology could significantly help to face this issue. In this paper, a numerical approach to analyze Nickel-Titanium TAV stent-frame behavior during in vitro durability tests is proposed. A simplified multi-stage strategy was adopted where, in each stage, only two of the three involved components are considered. As a proof-of-concept the method was applied to a TAV prototype. Despite its simplifications, the developed computational framework gave useful insights into the stent-frame failures behaviour during a fatigue test. Numerical results agree with experimental findings. In particular, the most dangerous condition was identified among a number of experimental tests, where different compartments and pressure gradients were investigated. The specific failure location was also correctly recognized. In conclusion, the presented methodology provides a tool to support the choice of proper testing conditions for the in vitro assessment of TAV fatigue behavior.

Copyright (c) 2017 by ASME
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