Simplified Multistage Computational Approach to Assess the Fatigue Behavior of a Niti Transcatheter Aortic Valve During In Vitro Tests: A Proof-of-Concept Study

Lorenza Petrini; Elena Dordoni; Dario Allegretti; Desiree Pott; Maximilian Kütting; Francesco Migliavacca; Giancarlo Pennati

doi:10.1115/1.4035791

Journal of Medical Devices | Volume 11 | Issue 2 | research-article

< Previous Article Next Article >

Research Papers

Simplified Multistage Computational Approach to Assess the Fatigue Behavior of a Niti Transcatheter Aortic Valve During In Vitro Tests: A Proof-of-Concept Study

Lorenza Petrini, Elena Dordoni, Dario Allegretti, Desiree Pott, Maximilian Kütting, Francesco Migliavacca and Giancarlo Pennati

[+] Author and Article Information

Lorenza Petrini

Department of Civil and
Environmental Engineering,
Politecnico di Milano,
Milano 20133, Italy

Elena Dordoni, Dario Allegretti, Francesco Migliavacca

Laboratory of Biological Structure Mechanics,
Department of Chemistry,
Materials and Chemical
Engineering “Giulio Natta,”
Politecnico di Milano,
Milano 20133, Italy

Desiree Pott, Maximilian Kütting

Department of Cardiovascular Engineering,
Institute of Applied Medical Engineering,
Helmholtz Institute,
RWTH Aachen University,
Aachen 52062, Germany

Giancarlo Pennati

Laboratory of Biological Structure Mechanics,
Department of Chemistry,
Materials and Chemical
Engineering “Giulio Natta,”
Politecnico di Milano,
Piazza Leonardo da Vinci 32,
Milano 20133, Italy
e-mail: giancarlo.pennati@polimi.it

¹Authors contributed equally.

²Corresponding author.

Manuscript received July 29, 2016; final manuscript received January 9, 2017; published online May 3, 2017. Assoc. Editor: Marc Horner.

J. Med. Devices 11(2), 021009 (May 03, 2017) (11 pages) Paper No: MED-16-1282; doi: 10.1115/1.4035791 History: Received July 29, 2016; Revised January 09, 2017

Article

References

Figures

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 multistage 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 behavior 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.

FIGURES IN THIS ARTICLE

Purchase this Content

$25.00

Purchase

Learn about subscription and purchase options

Your Session has timed out. Please sign back in to continue.

References

Zajarias, A. , and Cribier, A. G. , 2009, “ Outcomes and Safety of Percutaneous Aortic Valve Replacement,” J. Am. Coll. Cardiol., 53(20), pp. 1829–1836. [CrossRef] [PubMed]

Dvir, D. , Webb, J. G. , Bleiziffer, S. , Pasic, M. , Waksman, R. , Kodali, S. , Barbanti, M. , Latib, A. , Schaefer, U. , Rodés-Cabau, J. , Treede, H. , Piazza, N. , Hildick-Smith, D. , Himbert, D. , Walther, T. , Hengstenberg, C. , Nissen, H. , Bekeredjian, R. , Presbitero, P. , Ferrari, E. , Segev, A. , de Weger, A. , Windecker, S. , Moat, N. E. , Napodano, M. , Wilbring, M. , Cerillo, A. G. , Brecker, S. , Tchetche, D. , Lefèvre, T. , De Marco, F. , Fiorina, C. , Petronio, A. S. , Teles, R. C. , Testa, L. , Laborde, J. C. , Leon, M. B. , and Kornowski, R. , and Valve-in-Valve International Data Registry Investigators, 2014, “ Transcatheter Aortic Valve Implantation in Failed Bioprosthetic Surgical Valves,” JAMA-J. Am. Med. Assoc., 312(2), pp. 162–170. [CrossRef]

Nishimura, R. A. , Otto, C. M. , Bonow, R. O. , Carabello, B. A. , Erwin, J. P., III , Guyton, R. A. , O'Gara, P. T. , Ruiz, C. E. , Skubas, N. J. , Sorajja, P. , Sundt, T. M., III , Thomas, J. D. , Anderson, J. L. , Halperin, J. L., Albert, N. M. , Bozkurt, B. , Brindis, R. G. , Creager, M. A. , Curtis, L. H. , DeMets, D. , Guyton, R. A. , Hochman, J. S. , Kovacs, R. J. , Ohman, E. M. , Pressler, S. J. , Sellke, F. W. , Shen, W. K. , Stevenson, W. G. , Yancy, C. W. , American College of Cardiology, American College of Cardiology/American Heart Association, and American Heart Association, 2014, “ AHA/ACC Guideline for the Management of Patients With Valvular Heart Disease: A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines,” J. Am. Coll. Cardiol., 63(22), pp. e57–e185. [CrossRef] [PubMed]

Makkar, R. R. , Fontana, G. P. , Jilaihawi, H. , Kapadia, S. , Pichard, A. D. , Douglas, P. S. , Thourani, V. H. , Babaliaros, V. C. , Webb, J. G. , Herrmann, H. C. , Bavaria, J. E. , Kodali, S. , Brown, D. L. , Bowers, B. , Dewey, T. M. , Svensson, L. G. , Tuzcu, M. , Moses, J. W. , Williams, M. R. , Siegel, R. J. , Akin, J. J. , Anderson, W. N. , Pocock, S. , Smith, C. R. , Leon, M. B. , and PARTNER Trial Investigators, 2012, “ Transcatheter Aortic-Valve Replacement for Inoperable Severe Aortic Stenosis,” N. Engl. J. Med., 366(18), pp. 1696–1704. [CrossRef] [PubMed]

Adams, D. H. , Popma, J. J. , Reardon, M. J. , Yakubov, S. J. , Coselli, J. S. , Deeb, G. M. , Gleason, T. G. , Buchbinder, M. , Hermiller, J. , Jr., Kleiman, N. S. , Chetcuti, S. , Heiser, J. , Merhi, W. , Zorn, G. , Tadros, P. , Robinson, N. , Petrossian, G. , Hughes, G. C. , Harrison, J. K. , Conte, J. , Maini, B. , Mumtaz, M. , Chenoweth, S. , Oh, J. K. , and U.S. CoreValve Clinical Investigators, 2014, “ Transcatheter Aortic Valve Replacement With a Self-Expanding Prosthesis,” N. Engl. J. Med., 370(19), pp. 1790–1798. [CrossRef] [PubMed]

Haussig, S. , Schuler, G. , and Linke, A. , 2014, “ World Wide TAVI Registries: What Have We Learned?,” Clin. Res. Cardiol., 103(8), pp. 603–612. [CrossRef] [PubMed]

Bonhoeffer, P. , Boudjemline, Y. , Saliba, Z. , Merckx, J. , Aggoun, Y. , Bonnet, D. , Acar, P. , Le Bidois, J. , Sidi, D. , and Kachaner, J. , 2000, “ Percutaneous Replacement of Pulmonary Valve in a Right-Ventricle to Pulmonary-Artery Prosthetic Conduit With Valve Dysfunction,” Lancet, 356(9239), pp. 1403–1405. [CrossRef] [PubMed]

Cribier, A. , Eltchaninoff, H. , Bash, A. , Borenstein, N. , Tron, C. , Bauer, F. , Derumeaux, G. , Anselme, F. , Laborde, F. , and Leon, M. , 2002, “ Percutaneous Transcatheter Implantation of an Aortic Valve Prosthesis for Calcific Aortic Stenosis: First Human Case Description,” Circulation, 106(24), pp. 3006–3008. [CrossRef] [PubMed]

Leon, M. , Smith, C. , Mack, M. , Miller, D. , Moses, J. , Svensson, L. , Tuzcu, E. , Webb, J. , Fontana, G. , Makkar, R. , Brown, D. , Block, P. , Guyton, R. , Pichard, A. , Bavaria, J. , Herrmann, H. , Douglas, P. , Petersen, J. , Akin, J. , Anderson, W. , Wang, D. , and Pocock, S. , 2010, “ Transcatheter Aortic Valve Implantation for Aortic Stenosis in Patients Who Cannot Undergo Surgery,” N. Engl. J. Med., 363(17), pp. 1597–1607. [CrossRef] [PubMed]

Piazza, N. , Bleiziffer, S. , Brockmann, G. , Hendrick, R. , Deutsch, M.-A. , Opitz, A. , Mazzitelli, D. , Tassani-Prell, P. , Schreiber, C. , and Lange, R. , 2011, “ Transcatheter Aortic Valve Implantation for Failing Surgical Aortic Bioprosthetic Valve: From Concept to Clinical Application and Evaluation—Part 1,” JACC: Cardiovasc. Interventions, 4(7), pp. 721–732. [CrossRef]

Milburn, K. , Bapat, V. , and Thomas, M. , 2014, “ Valve-in-Valve Implantations: Is This the New Standard for Degenerated Bioprostheses? Review of the Literature,” Clin. Res. Cardiol., 103(6), pp. 417–429. [CrossRef] [PubMed]

Webb, J. , Pasupati, S. , Humphries, K. , Thompson, C. , Altwegg, L. , Moss, R. , Sinhal, A. , Carere, R. , Munt, B. , Ricci, D. , Ye, J. , Cheung, A. , and Lichtenstein, S. , 2007, “ Percutaneous Transarterial Aortic Valve Replacement in Selected High-Risk Patients With Aortic Stenosis,” Circulation, 116(7), pp. 755–763. [CrossRef] [PubMed]

Piazza, N. , Grube, E. , Gerckens, U. , den Heijer, P. , Linke, A. , Luha, O. , Ramondo, A. , Ussia, G. , Wenaweser, P. , Windecker, S. , Laborde, J. , de Jaegere, P. , and Serruys, P. , 2008, “ Procedural and 30-Day Outcomes Following Transcatheter Aortic Valve Implantation Using the Third Generation (18 fr) Corevalve Revalving System: Results From the Multicentre, Expanded Evaluation Registry 1-Year Following CE Mark Approval,” Eurointervention, 4(2), pp. 242–249. [CrossRef] [PubMed]

ISO, 2013, “ Cardiovascular Implants—Cardiac Valce Prostheses,” International Standard Organization, Geneva, Switzerland.

Nordmeyer, J. , Coats, L. , Lurz, P. , Lee, T.-Y. , Derrick, G. , Rees, P. , Cullen, S. , Taylor, A. , Khambadkone, S. , and Bonhoeffer, P. , 2008, “ Percutaneous Pulmonary Valve-in-Valve Implantation: A Successful Treatment Concept for Early Device Failure,” Eur. Heart J., 29(6), pp. 810–815. [CrossRef] [PubMed]

McElhinney, D. , Hellenbrand, W. , Zahn, E. , Jones, T. , Cheatham, J. , Lock, J. , and Vincent, J. , 2010, “ Short- and Medium-Term Outcomes After Transcatheter Pulmonary Valve Placement in the Expanded Multicenter U.S. Melody Valve Trial,” Circulation, 122(5), pp. 507–516. [CrossRef] [PubMed]

McElhinney, D. B. , Cheatham, J. P. , Jones, T. K. , Lock, J. E. , Vincent, J. A. , Zahn, E. M. , and Hellenbrand, W. E. , 2011, “ Stent Fracture, Valve Dysfunction, and Right Ventricular Outflow Tract Reintervention After Transcatheter Pulmonary Valve Implantation: Patient-Related and Procedural Risk Factors in the U.S. Melody Valve Trial,” Circ. Cardiovasc. Interventions, 4(6), pp. 602–614. [CrossRef]

Fleming, G. , Hill, K. , Green, A. , and Rhodes, J. , 2012, “ Percutaneous Pulmonary Valve Replacement,” Prog. Pediatr. Cardiol., 33(2), pp. 143–150. [CrossRef]

Ussia, G. P. , Barbanti, M. , Petronio, A. S. , Tarantini, G. , Ettori, F. , Colombo, A. , Violini, R. , Ramondo, A. , Santoro, G. , Klugmann, S. , Bedogni, F. , Maisano, F. , Marzocchi, A. , Poli, A. , De Carlo, M. , Napodano, M. , Fiorina, C. , De Marco, F. , Antoniucci, D. , de Cillis, E. , Capodanno, D. , and Tamburino, C. , 2012, “ Transcatheter Aortic Valve Implantation: 3-Year Outcomes of Self-Expanding CoreValve Prosthesis,” Eur. Heart J., 33(8), pp. 969–976. [CrossRef] [PubMed]

Bouleti, C. , Himbert, D. , Iung, B. , Alos, B. , Kerneis, C. , Ghodbane, W. , Messika-Zeitoun, D. , Brochet, E. , Fassa, A. A. , Depoix, J. P. , Ou, P. , Nataf, P. , and Vahanian, A. , 2015, “ Long-Term Outcome After Transcatheter Aortic Valve Implantation,” Heart, 101(12), pp. 936–942. [CrossRef] [PubMed]

Kovac, J. , Schuler, G. , Gerckens, U. , Müller, R. , Serruys, P. W. , Bonan, R. , Labinaz, M. , den Heijer, P. , Mullen, M. , Tymchak, W. , and Grube, E. , 2016, “ Four-Year Experience With the CoreValve Transcatheter Heart Valve,” EuroIntervention, 12(8), pp. e1039–e1046. [CrossRef] [PubMed]

Arsalan, M. , and Walther, T. , 2016, “ Durability of Prostheses for Transcatheter Aortic Valve Implantation,” Nat. Rev. Cardiol., 13(6), pp. 360–367. [CrossRef] [PubMed]

Padala, M. , Sarin, E. , Willis, P. , Babaliaros, V. , Block, P. , Guyton, R. , and Thourani, V. , 2010, “ An Engineering Review of Transcatheter Aortic Valve Technologies,” Cardiovasc. Eng. Technol., 1(1), pp. 77–87. [CrossRef]

Sun, W. , Sacks, M. , Fulchiero, G. , Lovekamp, J. , Vyavahare, N. , and Scott, M. , 2004, “ Response of Heterograft Heart Valve Bio-Materials to Moderate Cyclic Loading,” J. Biomed. Mater. Res. Part A, 69A(4), pp. 658–669. [CrossRef]

Zubiate, B. , and Sacks, M. S. , 2010, “ Effects of Cyclic Flexural Fatigue on Porcine Bioprosthetic Heart Valve Heterograft Biomaterials,” J. Biomed. Mater. Res. Part A., 94A(1), pp. 205–213. [CrossRef]

Cacciola, G. , Peters, G. W. M. , and Schreurs, P. J. G. , 2000, “ A Three-Dimensional Mechanical Analysis of a Stentless Fibre-Reinforced Aortic Valve Prosthesis,” J. Biomech., 33(5), pp. 521–530. [CrossRef] [PubMed]

Abbasi, M. , and Azadani, A. N. , 2015, “ Leaflet Stress and Strain Distributions Following Incomplete Transcatheter Aortic Valve Expansion,” J. Biomech., 48(13), pp. 3663–3671. [CrossRef] [PubMed]

Martin, C. , and Sun, W. , 2015, “ Comparison of Transcatheter Aortic Valve and Surgical Bioprosthetic Valve Durability: A Fatigue Simulation Study,” J. Biomech., 48(12), pp. 3026–3034. [CrossRef] [PubMed]

Early, M. , and Kelly, D. , 2011, “ The Consequences of the Mechanical Environment of Peripheral Arteries for Nitinol Stenting,” Med. Biol. Eng. Comput., 49(11), pp. 1279–1288. [CrossRef] [PubMed]

Harvey, S. , 2011, “ Nitinol Stent Fatigue in a Peripheral Human Artery Subjected to Pulsatile and Articulation Loading,” J. Mater. Eng. Perform., 20(4), pp. 697–705. [CrossRef]

Grujicic, M. , Pandurangan, B. , Arakere, A. , and Snipes, J. , 2012, “ Fatigue Life Computational Analysis for the Self-Expanding Endovascular Nitinol Stents,” J. Mater. Eng. Perform., 21(11), pp. 2218–2230. [CrossRef]

Meoli, A. , Dordoni, E. , Petrini, L. , Migliavacca, F. , Dubini, G. , and Pennati, G. , 2013, “ Computational Modeling of In Vitro Set-Ups for Peripheral Self-Expanding Nitinol Stents: The Importance of Stent-Wall Interaction in the Assessment of the Fatigue Resistance,” Cardiovasc. Eng. Technol., 4(4), pp. 474–484. [CrossRef]

Dordoni, E. , Meoli, A. , Wu, W. , Dubini, G. , Migliavacca, F. , Pennati, G. , and Petrini, L. , 2014, “ Fatigue Behavior of Nitinol Peripheral Stents: The Role of Plaque Shape Studied With Computational Structural Analyses,” Med. Eng. Phys., 36(7), pp. 842–849. [CrossRef] [PubMed]

Meoli, A. , Dordoni, E. , Petrini, L. , Migliavacca, F. , Dubini, G. , and Pennati, G. , 2014, “ Computational Study of Axial Fatigue for Peripheral Nitinol Stents,” J. Mater. Eng. Perform., 23(7), pp. 2606–2613. [CrossRef]

Kumar, G. P. , Cui, F. , Danpinid, A. , Su, B. , Hon, J. , and Leo, H. , 2013, “ Design and Finite Element-Based Fatigue Prediction of a New Self-Expandable Percutaneous Mitral Valve Stent,” Comput. Aided Des., 45(10), pp. 1153–1158. [CrossRef]

Vaesken, A. , Khoffi, F. , Heim, F. , Dieval, F. , and Chakfe, N. , 2016, “ Fiber Heart Valve Prosthesis: Early In Vitro Fatigue Results,” J. Biomed. Mater. Res. B Appl. Biomater., 104(5), pp. 986–992 [CrossRef] [PubMed]

Yousefi, A. , Vaesken, A. , Amri, A. , Dasi, L. P. , and Heim, F. , 2016, “ Heart Valves From Polyester Fibers vs. Biological Tissue: Comparative Study In Vitro,” Ann. Biomed. Eng. (Online).

Bezuidenhout, D. , Williams, D. F. , and Zilla, P. , 2015, “ Polymeric Heart Valves for Surgical Implantation, Catheter-Based Technologies and Heart Assist Devices,” Biomaterials, 36, pp. 6–25. [CrossRef] [PubMed]

Funakubo, H. , 1987, Shape Memory Alloys, Gordon and Breach Science Publishers, New York.

Otsuka, K. , and Wayman, C. M. , 1998, Shape Memory Materials, Cambridge University Press, Cambridge, UK.

Robertson, S. W. , and Ritchie, R. O. , 2007, “ In Vitro Fatigue-Crack Growth and Fracture Toughness Behavior of Thin-Walled Superelastic Nitinol Tube for Endovascular Stents: A Basis for Defining the Effect of Crack-Like Defects,” Biomaterials, 28(4), pp. 700–709. [CrossRef] [PubMed]

Petrini, L. , Wu, W. , Dordoni, E. , Meoli, A. , Migliavacca, F. , and Pennati, G. , 2012, “ Fatigue Behavior Characterization of Nitinol for Peripheral Stents,” Funct. Mater. Lett., 5(1), p. 1250012. [CrossRef]

Auricchio, F. , Taylor, R. L. , and Lubliner, J. , 1997, “ Shape-Memory Alloys: Macromodeling and Numerical Simulations of the Superelastic Behavior,” Comput. Methods Appl. Mech. Eng., 146(1), pp. 281–312. [CrossRef]

Auricchio, F. , 2001, “ A Robust Integration-Algorithm for a Finite-Strain Shapememory-Alloy Superelastic Model,” Int. J. Plast., 17(7), pp. 971–990. [CrossRef]

Zhao, S. , Gu, L. , and Froemming, S. , 2012, “ Performance of Self-Expanding Nitinol Stent in a Curved Artery: Impact of Stent Length and Deployment Orientation,” ASME J. Biomech. Eng., 134(7), p. 071007. [CrossRef]

Azaouzi, M. , Makradi, A. , and Belouettar, S. , 2012, “ Deployment of a Self-Expanding Stent Inside an Artery: A Finite Element Analysis,” Mater. Des., 41, pp. 410–420. [CrossRef]

Pelton, A. , Schroeder, V. , Mitchell, M. , Gong, X. , Barney, M. , and Robertson, S. , 2008, “ Fatigue and Durability of Nitinol Stents,” J. Mech. Behav. Biomed. Mater., 1(2), pp. 153–164. [CrossRef] [PubMed]

Runciman, A. , Xu, D. , Pelton, A. R. , and Ritchie, R. O. , 2011, “ An Equivalent Strain/Coffin-Manson Approach to Multiaxial Fatigue and Life Prediction in Superelastic Nitinol Medical Devices,” Biomaterials, 32(22), pp. 4987–4993. [CrossRef] [PubMed]

Morgan, N. B. , Painter, J. , and Moffat, A. , 2003, “ Mean Strain Effects and Microstructural Observations During In Vitro Fatigue Testing of NiTi,” SMST-2003: Proceedings of the International Conference on Shape Memory and Superelastic Technologies, A. R. Pelton and T. W. Duerig, eds., International Organization on SMST, Pacific Grove, CA, pp. 303–310.

Robertson, S. W. , Pelton, A. R. , and Ritchie, R. O. , 2012, “ Mechanical Fatigue and Fracture of Nitinol,” Int. Mater. Rev., 57(1), pp. 1–36. [CrossRef]

Figures

Fig. 1

Experimental setup and tested valve prototype: (a) self-expandable transcatheter aortic valve within the silicone compartment, (b) multichambers durability tester with a detail of the mounted compartment and valve, (c) sketch of the durability tester describing the main components, and (d) typical pressure waveforms (TOP and BOTTOM) applied during a durability test, with a maximum pressure drop (Δp) of about 100 mmHg (13.3 kPa)

View Large | Save Figure | Download Slide (.ppt)

Fig. 2

Boundary conditions for fatigue simulations (for sake of visualization clearness, a third of the full geometry is shown): instead of considering all the three valve components and the sole internal negative pressure as in reality (a), the leaflets are not considered and the reaction forces exerted by the leaflets on the stent-frame are applied while the pressure acts only on the compartment inner surface (b)

View Large | Save Figure | Download Slide (.ppt)

Fig. 3

Numerical simulations workflow: Boxes and ellipses represent geometrical models and FE analyses (FEA), respectively. At the end of the process, the mean and alternating strains throughout the stent-frame are calculated to be used in the constant-life diagram for fatigue evaluation.

View Large | Save Figure | Download Slide (.ppt)

Fig. 4

Creation of the aortic valve stent-frame FE model: (a) 2D planar sketch for the laser cutting process, (b) 3D valve model in the postlaser cutting configuration, (c) surfaces used to simulate the valve expansion process

View Large | Save Figure | Download Slide (.ppt)

Fig. 5

Comparison between (a) the expanded stent-frame model and (b) the real expanded valve configuration in terms of diameters measured (mm) at five different levels

View Large | Save Figure | Download Slide (.ppt)

Fig. 6

(a) Average experimental tensile result versus computational fit and (b) material model parameters NiTi

View Large | Save Figure | Download Slide (.ppt)

Fig. 7

Crimp and deployment of the valve stent-frame model inside the compartment: (a) undeformed configuration with fully expanded valve, silicone compartment and cylindrical rigid surface for crimp—the imposed boundary conditions are indicated, (b) stent-frame crimped configuration, (c) after self-expansion inside the compartment, and (d) stand-alone model of the deformed valve stent-frame after the deployment inside the silicone compartment

View Large | Save Figure | Download Slide (.ppt)

Fig. 9

Crimping results. Numerical results in terms of equivalent Von Mises strain, with valve crimped at 14 mm (a) and 10 mm OD (b). Boxes detail the most stressed zones, corresponding to the bottom leaflet attachment tip and V-strut tip. (c) Images of the most critical zones (dashed lines) throughout the valve, before (left) and after (right) a crimping test down to 10 mm OD and subsequent self-expansion: the valve does not recover its original shape.

View Large | Save Figure | Download Slide (.ppt)

Fig. 8

Simulation to deduce the forces acting on the stent frame due to closing pressure, as transmitted by the leaflets: (a) deformed valve stent-frame model as after the deployment inside the silicone compartment, with added PU leaflets almost closed—the portion used for the simulation of leaflets closure is highlighted, (b) boundary conditions for the simulation of leaflet closure against a fixed rigid wall, (c) valve configuration after simulation of leaflets coaptation, and (d) the forces acting on the stent are evaluated to be used for the fatigue analysis

View Large | Save Figure | Download Slide (.ppt)

Fig. 10

Alternating equivalent strain values (ε_a) through the stent-frame, in case of different compartments: low (LO) and high (HO),oversizing, standard (SS) lower (LS) and higher (HS) stiffness. Peculiar stent-frame zones (TLA = top leaflets attachment edge, MLA = medium leaflets attachment edge, V-S = V-strut tip, BLA = bottom leaflets attachment edge) are shown in detail, with bolded boxes corresponding to areas where ε_a reach the maximum values.

View Large | Save Figure | Download Slide (.ppt)

Fig. 11

Numerical results obtained for Δp = 100 mmHg: Constant-life diagrams for low (a) and high oversizing (b) compartments with different stiffness (LS, SS, HS). ε_a = alternating strains, ε_m = mean strains, E_comp = compartment elastic modulus.

View Large | Save Figure | Download Slide (.ppt)

Fig. 12

(a) Constant-life diagram for the simulations mimicking the two in vitro investigated cases (HO-LS: compartment with high oversizing and soft compartment, LO-SS: compartment with low oversizing and standard material) and increased pressure drop across the leaflets (Δp = 150 mmHg = 20 kPa). For HO-LS case, some points of the stent-frame reach very high values of alternating strains, indicating a very likely fatigue failure. (b) Stent frame failure as experimentally observed: the fracture location, at the upper leaflet attachment edge, corresponds to the most risky points indicated by FEA. ε_a = alternating strains, ε_m = mean strains.

$(a) Constant-life diagram for the simulations mimicking the two in vitro investigated cases (HO-LS: compartment with high oversizing and soft compartment, LO-SS: compartment with low oversizing and standard material) and increased pressure drop across the leaflets (Δp = 150 mmHg = 20 kPa). For HO-LS case, some points of the stent-frame reach very high values of alternating strains, indicating a very likely fatigue failure. (b) Stent frame failure as experimentally observed: the fracture location, at the upper leaflet attachment edge, corresponds to the most risky points indicated by FEA. εa = alternating strains, εm = mean strains.$

View Large | Save Figure | Download Slide (.ppt)

Tables

Errata

Discussions

Web of Science® Times Cited: 0

Some tools below are only available to our subscribers or users with an online account.

PDF
Email

You must be logged in as an individual user to share content.

Return to: Simplified Multistage Computational Approach to Assess the Fatigue Behavior of a Niti Transcatheter Aortic Valve During In Vitro Tests: A Proof-of-Concept Study

Copyright in the material you requested is held by the American Society of Mechanical Engineers (unless otherwise noted). This email ability is provided as a courtesy, and by using it you agree that you are requesting the material solely for personal, non-commercial use, and that it is subject to the American Society of Mechanical Engineers' Terms of Use. The information provided in order to email this topic will not be used to send unsolicited email, nor will it be furnished to third parties. Please refer to the American Society of Mechanical Engineers' Privacy Policy for further information.
Share
Get Citation

Petrini L, Dordoni E, Allegretti D, et al. Simplified Multistage Computational Approach to Assess the Fatigue Behavior of a Niti Transcatheter Aortic Valve During In Vitro Tests: A Proof-of-Concept Study. ASME. J. Med. Devices. 2017;11(2):021009-021009-11. doi:10.1115/1.4035791.

Download citation file:

RIS (Zotero)

EndNote

BibTex

Medlars

ProCite

RefWorks

Reference Manager

© Copyright
Get Alerts

Processing your request... Please Wait.

Simplified Multistage Computational Approach to Assess the Fatigue Behavior of a Niti Transcatheter Aortic Valve During In Vitro Tests: A Proof-of-Concept Study

Abstract

FIGURES IN THIS ARTICLE

References

Figures

Tables

Errata

Discussions

Related Content

Journals

Conference Proceedings

eBooks