Document Type : Full Research Paper


1 Ph.D. Student, Biological Fluid Dynamics Research Laboratory, Department of Biomedical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran

2 Associate Professor, Biological Fluid Dynamics Research Laboratory, Department of Biomedical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran

3 Assistant Professor, Biological Fluid Dynamics Research Laboratory, Department of Biomedical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran



Transcatheter aortic valves have become the standard procedure for high-risk patients with severe aortic valve stenosis. This minimally invasive procedure can expand to a wider range of patients with a lower risk of surgery. The complications after the implantation and the structural malfunction of these prostheses are the obstacles of this transition. Design optimization of the stents of these prostheses can improve their performance and reduce the post-operative complications associated with them. Since all prostheses are crimped before implantation, the designs should guarantee an acceptable structural performance after expansion, especially self-expandable stents for which the fatigue behavior strongly depends on the strain. This study applies a simple, cost-effective optimization framework to optimize the geometric parameters of these stents regarding the maximum strain during the crimping process. The design parameters include diameter profile, cell size, number of repeating components, and strut cross-section. The simplified models are evaluated and verified by the 3D simulations. The results show that the middle cells' height, number of cells, and strut width have the most prominent effect on the maximum crimping strain of the stent. The maximum strain of the optimized stent in the selected design space was 0.52. This stent had a width of 0.2 mm, thickness of 0.3 mm, the number of cells and patterns of 3 and 15, respectively, and the diameter profile associated with the diameter ratio of 1.05. This framework can be applied to a wide range of stent designs and tremendously reduce the cost of stent design and optimization.


Main Subjects

  1. Baumgartner, J. Hung, J. Bermejo, J.B. Chambers, A. Evangelista, B.P. Griffin, B. Iung, C.M. Otto, P.A. Pellikka, M. Quiñones, "Echocardiographic assessment of valve stenosis: EAE/ASE recommendations for clinical practice", Eur. J. Echocardiogr. 10 (2009) 1–25.
  2. P.J.P. Fanning, D.G.D.G. Platts, D.L.D.L. Walters, J.F.J.F. Fraser, "Transcatheter aortic valve implantation (TAVI): Valve design and evolution", Int. J. Cardiol. 168 (2013) 1822–31.
  3. J. Mack, M.B. Leon, C.R. Smith, D.C. Miller, J.W. Moses, E.M. Tuzcu, J.G. Webb, P.S. Douglas, W.N. Anderson, E.H. Blackstone, S.K. Kodali, R.R. Makkar, G.P. Fontana, S. Kapadia, J. Bavaria, R.T. Hahn, V.H. Thourani, V. Babaliaros, A. Pichard, H.C. Herrmann, D.L. Brown, M. Williams, M.J. Davidson, L.G. Svensson, J. Akin, "5-year outcomes of transcatheter aortic valve replacement or surgical aortic valve replacement for high surgical risk patients with aortic stenosis (PARTNER 1): A randomised controlled trial", Lancet. 385 (2015) 2477–2484.
  4. Sedrakyan, S.S. Dhruva, J. Shuhaiber, "Transcatheter Aortic Valve Replacement in Younger Individuals", JAMA Intern. Med. 177 (2017) 159.
  5. J. Popma, G. Michael Deeb, S.J. Yakubov, M. Mumtaz, H. Gada, D. O’Hair, T. Bajwa, J.C. Heiser, W. Merhi, N.S. Kleiman, J. Askew, P. Sorajja, J. Rovin, S.J. Chetcuti, D.H. Adams, P.S. Teirstein, G.L. Zorn, J.K. Forrest, D. Tchétché, J. Resar, A. Walton, N. Piazza, B. Ramlawi, N. Robinson, G. Petrossian, T.G. Gleason, J.K. Oh, M.J. Boulware, H. Qiao, A.S. Mugglin, M.J. Reardon, "Transcatheter aortic-valve replacement with a self-expanding valve in low-risk patients", N. Engl. J. Med. 380 (2019) 1706–1715.
  6. P. Bocchino, F. Angelini, B. Alushi, F. Conrotto, G.M. Cioffi, G. Tersalvi, G. Senatore, G. Pedrazzini, G.M. De Ferrari, L. Biasco, "Transcatheter Aortic Valve Replacement in Young Low-Risk Patients With Severe Aortic Stenosis: A Review", Front. Cardiovasc. Med. 7 (2020) 342.
  7. Doshi, "Extended benefits of TAVR in young patients with low-intermediate risk score: proceed with care", EuroIntervention. 14 (2018) e485.
  8. Athappan, E. Patvardhan, E.M. Tuzcu, L.G. Svensson, P.A. Lemos, C. Fraccaro, G. Tarantini, J.M. Sinning, G. Nickenig, D. Capodanno, C. Tamburino, A. Latib, A. Colombo, S.R. Kapadia, "Incidence, predictors, and outcomes of aortic regurgitation after transcatheter aortic valve replacement: Meta-analysis and systematic review of literature", J. Am. Coll. Cardiol. 61 (2013) 1585–1595.
  9. Cannata, D. Regazzoli, G. Barberis, M. Chiarito, P.P. Leone, V. Lavanco, G.G. Stefanini, G. Ferrante, P. Pagnotta, R. Bragato, E. Corrada, L. Torracca, G. Condorelli, B. Reimers, "Mitral Valve Stenosis after Transcatheter Aortic Valve Replacement: Case Report and Review of the Literature", Cardiovasc. Revascularization Med. 20 (2019) 1196–1202.
  10. Campelo-Parada, L. Nombela-Franco, M. Urena, A. Regueiro, P. Jiménez-Quevedo, M. Del Trigo, C. Chamandi, T. Rodríguez-Gabella, V. Auffret, O. Abdul-Jawad Altisent, R. DeLarochellière, J.-M. Paradis, E. Dumont, F. Philippon, N. Pérez-Castellano, R. Puri, C. Macaya, J. Rodés-Cabau, "Timing of Onset and Outcome of New Conduction Abnormalities Following Transcatheter Aortic Valve Implantation: Role of Balloon Aortic Valvuloplasty", Rev. Española Cardiol. (English Ed. 71 (2018) 162–169.
  11. Cao, S.C. Ang, M.P. Vallely, M. Ng, M. Adams, M. Wilson, "Migration of the transcatheter valve into the left ventricle"., Ann. Cardiothorac. Surg. 1 (2012) 243–244.
  12. Morganti, N. Brambilla, A.S. Petronio, A. Reali, F. Bedogni, F. Auricchio, "Prediction of patient-specific post-operative outcomes of TAVI procedure: The impact of the positioning strategy on valve performance", J. Biomech. 49 (2016) 2513–2519.
  13. Finotello, R.M. Romarowski, R. Gorla, G. Bianchi, F. Bedogni, F. Auricchio, S. Morganti, "Performance of high conformability vs. high radial force devices in the virtual treatment of TAVI patients with bicuspid aortic valve", Med. Eng. Phys. 89 (2021) 42–50.
  14. Mao, Q. Wang, S. Kodali, W. Sun, P.A. Root, "Numerical Parametric Study of Paravalvular Leak Following a Transcatheter Aortic Valve Deployment into a Patient-Specific Aortic Root", J. Biomech. Eng. 140 (2018) 1–11.
  15. Bianchi, G. Marom, R.P. Ghosh, O.M. Rotman, P. Parikh, L. Gruberg, D. Bluestein, "Patient-specific simulation of transcatheter aortic valve replacement: impact of deployment options on paravalvular leakage", Biomech. Model. Mechanobiol. 18 (2019) 435–451.
  16. Luraghi, F. Migliavacca, A. García-González, C. Chiastra, A. Rossi, D. Cao, G. Stefanini, J.F. Rodriguez Matas, "On the Modeling of Patient-Specific Transcatheter Aortic Valve Replacement: A Fluid–Structure Interaction Approach", Cardiovasc. Eng. Technol. 10 (2019) 437–455.
  17. P. Ghosh, G. Marom, M. Bianchi, K. D’souza, W. Zietak, D. Bluestein, "Numerical evaluation of transcatheter aortic valve performance during heart beating and its post-deployment fluid–structure interaction analysis", Biomech. Model. Mechanobiol. 19 (2020) 1725–1740.
  18. Rocatello, G. De Santis, S. De Bock, M. De Beule, P. Segers, P. Mortier, "Optimization of a Transcatheter Heart Valve Frame Using Patient-Specific Computer Simulation", Cardiovasc. Eng. Technol. 10 (2019) 456–468.
  19. Carbonaro, D. Gallo, U. Morbiducci, A. Audenino, C. Chiastra, "In silico biomechanical design of the metal frame of transcatheter aortic valves: multi-objective shape and cross-sectional size optimization", Struct. Multidiscip. Optim. (2021) 0–3.
  20. Barati, N. Fatouraee, M. Nabaei, F. Berti, L. Petrini, F. Migliavacca, J.F. Rodriguez Matas, "A computational optimization study of a self-expandable transcatheter aortic valve", Comput. Biol. Med. 139 (2021) 104942.
  21. Petrini, W. Wu, E. Dordoni, A. Meoli, F. Migliavacca, G. Pennati, "Fatigue behavior characterization of nitinol for peripheral stents", Funct. Mater. Lett. 5 (2012).
  22. R. Pelton, V. Schroeder, M.R. Mitchell, X.Y. Gong, M. Barney, S.W. Robertson, "Fatigue and durability of Nitinol stents", J. Mech. Behav. Biomed. Mater. 1 (2008) 153–164.
  23. Qiu, M. Barakat, B. Hopkins, S. Ravaghi, A.N. Azadani, "Transcatheter aortic valve replacement in bicuspid valves: The synergistic effects of eccentric and incomplete stent deployment", J. Mech. Behav. Biomed. Mater. 121 (2021) 104621.
  24. Dordoni, "Fatigue analysis of Nitinol cardiovascular devices". PhD Thesis, Politecnico di Milano, 2014.
  25. Pfensig, S. Kaule, R. Ott, C. Wüstenhagen, M. Stiehm, J. Keiler, A. Wree, N. Grabow, K.P. Schmitz, S. Siewert, "Numerical simulation of a transcatheter aortic heart valve under application-related loading", Curr. Dir. Biomed. Eng. 4 (2018) 185–189.
  26. Bosmans, N. Famaey, E. Verhoelst, J. Bosmans, J. Vander Sloten, "A validated methodology for patient specific computational modeling of self-expandable transcatheter aortic valve implantation", J. Biomech. 49 (2016) 2824–2830.
  27. Pant, G. Limbert, N.P. Curzen, N.W. Bressloff," Multiobjective design optimisation of coronary stents", Biomaterials. 32 (2011) 7755–7773.
  28. S. Cabrera, C.W.J. Oomens, F.P.T. Baaijens, "Understanding the requirements of self-expandable stents for heart valve replacement: Radial force, hoop force and equilibrium", J. Mech. Behav. Biomed. Mater. 68 (2017) 252–264.
  29. Masoumi Khalil Abad, D. Pasini, R. Cecere, "Shape optimization of stress concentration-free lattice for self-expandable Nitinol stent-grafts", J. Biomech. 45 (2012) 1028–1035.