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Residual stresses in coronary artery stents
D Möller1, W Reimers, A Pyzalla
1Hahn-Meitner-Institut, Bereich Strukturforschung, Glienicker Str. 100, 14109 Berlin, Germany.
Insights
Coronary artery stents experience residual stresses from crimping and expansion, impacting their mechanical properties. Understanding these stresses is crucial for developing fail-safe criteria for coronary stents.
Area of Science:
- Biomedical Engineering
- Materials Science
- Cardiovascular Research
Background:
- Coronary heart disease, caused by coronary sclerosis, is a leading cause of death in Western countries.
- The stent technique, developed in the 1980s, is widely used to maintain arterial patency in patients with coronary artery disease.
- Stents, available in self-expanding and balloon-expanding types, are implanted via catheter to open narrowed arteries.
Purpose of the Study:
- To analyze residual stresses in coronary stents after crimping and expansion.
- To investigate the impact of these residual stresses on stent mechanical properties.
- To contribute to the development of reliable fail-safe criteria for coronary stents.
Main Methods:
- Discussion of residual stresses generated during stent crimping (compression) and expansion (implantation).
- Analysis of how these stresses are stored within the stent structure post-implantation.
- Consideration of superimposed stresses from cyclic heartbeats over a patient's lifetime.
Main Results:
- Residual stresses are inherent in both self-expanding and balloon-expanding stents after implantation procedures.
- These stresses are superimposed on the dynamic stresses from millions of heartbeats.
- The study highlights the complex mechanical environment coronary stents operate within.
Conclusions:
- Residual stresses are a critical factor in the long-term performance of coronary stents.
- Further research into these stresses is necessary for establishing robust safety and efficacy standards.
- This work supports interdisciplinary efforts to ensure the mechanical reliability of cardiovascular implants.
Abstract:
In western industrial countries, coronary heart disease is the most common cause of death. The reason is a coronary sclerosis, which by the generation of plaques narrows the inner lumen of an artery and, thus, deteriorates the blood supply. This leads to symptoms like burning pain or increased pressure in the chest, and finally to an under supply and damage of the heart muscle. In order to keep those portions of arteries that are covered by a plaque open, the stent technique was developed in the 1980s and is increasingly used since about 13 years. These stents are usually made of wires or of a slotted tube and are of two kinds: self-expanding and balloon expanding. Both types are implanted after being mounted on a catheter and expanded in the desired position. Self-expanding stents make use of the elastic deformation, while the other group of stents are expanded by a balloon, which brings about a plastic deformation of certain regions of the stent structure. Thus, after implantation, parts of these stents undergo two steps of distinct plastic deformation. First during compression, which is necessary for the mounting procedure on the catheter (crimping), and second during expansion for implantation. In this article, the residual stresses generated during crimping and expansion are presented and discussed. These stresses are stored in the structure of a portion of a stent after implantation and are superimposed on those stresses generated by the more than 700 million cyclic heart beats during the patient's life. This work is a part of several interdisciplinary research projects by the authors in order to gain reliable fail-safe criteria for the static and cyclic mechanical properties of coronary stents.