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Thursday, May 11, 2006 - 10:50 AM
MEM14.1

The V-Crown – A Novel Proximal NiTi-Structure for Thoracic Aortic Arch Stentgrafts

R. Kaufmann, Jotec GmbH, Hechingen, Germany; M. Mertmann, Memry GmbH, Weil am Rhein, Germany

The paper describes all design and manufacturing related aspects of the development of the so-called V-Crown, a proximal superelastic NiTi structure for use in therapy of thoracic aortic aneurysms or dissections. The V-crown facilitates the implantation of the thoracic stentgraft system ‘E-vita’ far beyond the subclavian artery within the aortic arch. Due to this, formerly contraindicated lesions can now  be treated.
Besides the description of the relevant design features this paper deals with the applied thermo-mechanical treatment of the NiTi wire which is used for the manufacturing of the superelastic zig-zag structure. Furthermore, a crimping process has been applied to close the open wire ends. The material used for the closure is also a NiTi tubular component which was made out of a superelastic tube. The crimping is carried out at a temperature around 500 °C in order to give the material enough workability for the necessary complex deformation.
Results of the stress-strain analysis achieved by FEA at reference models as well as animal tests are presented. Finally, first clinical cases demonstrated that the developed stent concept provides a reliable and stable design option for endovascular aortic arch therapy. The European market approval is already granted.

Summary: Stentgrafting of thoracic aortic aneurysms or dissections becomes a more and more common therapy in opposite to the classical surgical approach. Based on anatomic constraints and requirements also related to deployment technology, a proximal superelastic NiTi-wire structure, the so called V-crown, was developed. The V-crown facilitates the implantation of the thoracic stentgraft system ‘E-vita’ far beyond the subclavian artery within the aortic arch. Due to this, formerly contraindicated lesions can now be treated. The paper describes relevant design features and manufacturing technologies. The main parameters of thermo-mechanical NiTi wire treatment as well as the wire fixation by means of crimping are discussed. Results of the stress-strain analysis achieved by FEA at reference models as well as animal tests are presented. Finally, first clinical cases demonstrated that the V-crown concept provides a reliable and stable design option for endovascular aortic arch therapy. The European market approval is already granted.