Design Method of Self-expanding Stent Suitable for Diverse Clinical Manifestation Based on Mechanical Properties

Stent placement has received a great deal of attention as a minimally invasive procedure for treating, for example, vascular stenotic lesions associated with coronary atherosclerosis. However, the long-term placement of stents can lead to the severe problem of in-stent restenosis in blood vessels. In-stent restenosis results from neointimal thickening from the hyperplasia of smooth muscle cells, caused by the stimulus of the force of the stent on the vascular wall. In the present study, a method to design a bare metal stent suitable for diverse clinical manifestation is proposed for lowering the risk of in-stent restenosis. The proposed method consists of a design method and a modification method. In the design method, a stent with mechanical properties sufficient to expand the stenotic part in a blood vessel is designed by applying the mechanical properties of the host blood vessel. The force on the vascular wall when inserting the designed stent is concentrated at both ends of the stent, and the force concentration provokes the hyperplasia of smooth muscle cells. As a result, the risk of in-stent restenosis increases. The modification method was introduced into the proposed method to solve the problem of force concentration. After modification, the force concentration at the stent ends was markedly relaxed. This new-generation stent has a nonuniform shape along its axial direction. Thus, the proposed method will enable us to provide a suitable stent with a lower risk of in-stent restenosis.