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Finite element analysis of stent expansion: Influence of stent geometry on performance parameters

Ischaemic heart diseases are a global health problem that have been increasing in the recent years [1]. Most of ischaemic heart diseases is caused by atherosclerosis, a clinical pathology characterized by the deposition of fatty material on the arteries walls what may lead to thickening, hardening and blocking of these blood vessels, reducing the blood flow. This situation can cause heart attack, stroke and, in extreme cases, death [1,2]. Balloon expandable stents are the most used technique in the treatment of these pathologies [1]. Although stainless steel, Niobium and CoCr alloys are the most used in stents manufacturing, new materials have been developed in the recent years, mainly biodegradables, once these solutions fulfil some unmet medical needs and do not require a second procedure to remove the device [3]. Magnesium alloys are one of the options. The main purpose of this work is the study of an AZ31 magnesium alloy stent expansion behaviour, without considering the contact definitions, by using the finite element method. A geometry composed by lozenges was simulated to study the required expansion pressure, equivalent plastic strain and other performance parameters (dogboning, foreshortening and recoil). The results were compared with those of a Palmaz-Schatz model. The obtained results showed that Lozenge model requires higher expansion pressures than Palmaz-Schatz model and has worse performance in terms of foreshortening and longitudinal recoil. In terms of dogboning, central and distal recoil the Lozenge model presents better results.