FINITE ELEMENT ANALYSIS OF PLLA CARDIOVASCULAR COILED STENT

Abstract

In cardiovascular field angioplasty plays an important role. It is widening of a blocked vessel by balloon catheter. Stent holds an important role in angioplasty. A stent is any medical device that supports tissue, but most commonly a stent refers to a specific medical device that is placed inside an artery after angiography to stop the artery from becoming blocked again. An arterial stent is a mesh like tube often made of metal/fiber that can expand through balloon expansion once it is inserted into an artery. The most common problems related to stents are improper expansion and restenosis inside the vessel. The balloon transfers the pressure as load to expand the stent. Restenosis is the narrowing of artery/blood vessel. This narrowing of vessel is due to the fact that stent strength decreases with time and mechanical load is passed to the surrounding tissue. This work presents the study carried out using carbon fiber composite poly-lactic acid as basic material for stent. The type of stent used was coiled. Stent expansion procedure was simulated using non-linear FEM model in Ansys, which is considered to be the best possible way to simulate expansion procedure for current design of stents. Interaction between balloon material and stent surface was modeled as frictional contact. The results of stent were analyzed with respect to stress, strain and deflection which mainly contribute to cause of restenosis. Two cases (i) Double-end constrained and (ii) single-end constrained were simulated with different boundary conditions of balloon expansion. Radial recoil, longitudinal recoil and axial displacement results were analyzed.