ИСТИНА

The aim of the study was the development of the methodology of the engineering approach to the assessment of the main functional and mechanical characteristics of intravascular polymer stents. The proposed approach allows identifying general behavior patterns of this type of structure, which is necessary for the analysis and selection of the combination of material and stent design. Methods. Discussion and substantiation of the list of the main functional and mechanical requirements for intravascular stents was conducted. An engineering mechanical model of stent behavior was developed while its opening and subsequent elastic recoil. Results. A formula for estimating the value of the recoil was obtained by the methods of strength of materials, which allows moving from the functional requirements for the stent to the requirements for the mechanical properties of the material used and the geometric characteristics of the stent elements. Recoil proved to be proportional to the ratio of the yield stress to the Young's modulus of the stent material and to the square of the ratio of the length of the stent elementary cell stratum to its width. As for example according to the engineering estimates, the material for the stent with Absorb design should have large ultimate strain:   20-50% (to ensure maximum stent development); sufficiently high yield strength: y  30 MPa (so that the stent does not collapse in the vessel); maximum E/y  50 (to reduce recoil). An assessment of the suitability of some typical bioresorbable materials according to these criteria was given.