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Publication Detail
Study of the radial force applied by transcatheter aortic valves on the left ventricular outflow tract
  • Publication Type:
  • Authors:
    Tzamtzis S, Viquerat J, Yap J, Mullen MJ, Burriesci G
  • Publication date:
  • Pagination:
    2212, ?
  • Name of conference:
    6th European Congress On Computational Methods In Applied Sciences And Engineering (ECCOMAS 2012)
  • Conference place:
    Vienna, Austria
  • Conference start date:
  • Conference finish date:
Transcatheter Aortic Valve Implantation (TAVI) avoids the need for open-heart surgery and eliminates some of the main risks associated with conventional invasive operations, such as the need for cardiac arrest/restart, general anaesthesia, thoracotomy and extracorporeal circulation; therefore it is suitable for the rapidly enlarging patients’ population excluded from surgery. Clinical experiences with this approach have clearly indicated that this is feasible and promising. However, they have also enlightened a number of limitations that still require to be addressed in order to improve the safety of the technique. In particular, one of the most critical issues in TAVI devices is the proper administration of the radial force applied by the prosthesis on the surrounding tissues to achieve a proper securing. This has to be sufficient to counter the action of the blood pressures, without perturbing the conduction system of the heart by applying excessive pressure on atrio-ventricular node and relative left bundle. This work presents a numerical study of the different mechanisms generating the force exchanged between the valve and the left ventricular outflow tract (LVOT) in the case of balloon expandable and self-expanding transcatheter aortic valves. In particular, the behaviour of the Medtronic CoreValve (self-expanding) and Edwards SAPIEN (balloon-expandable) valve devices, both of size 26, were simulated and compared. Finite element models of the frames of the two prostheses were created, based on the measurements on the actual valves, simulating the manufacturing shape-setting process in the case of the CoreValve. The material properties were determined from mechanical tests performed on valve components. The models were used to simulate in MSC.Marc the release mechanism for the two devices, and determine the hoop forces established on the LVOT. In the case of the SAPIEN, the model of the catheter balloon was included to reproduce the standard implantation procedure. Results indicate that the radial force produced by both solutions is characterised by large variability within their recommended range of implantation. In the case of the self-expanding valve, the radial force depends essentially on the diameter of the left ventricular outflow tract, while for the balloon-expandable valve it is essentially influenced by both the geometry and compliance of the host tissues. The outcomes of this study provide useful information and could support a more cautious selection of the recommended implantation sizes, as well as the development of improved solutions.
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