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A Quick Tour of the COMSOL Modeling Environment
Published in Guigen Zhang, Introduction to Integrative Engineering, 2017
Here, let us have a look at an example to see how useful this geometric parameterization capability is. Figure 14.16 shows an example in which a model of a coronary stent is built in COMSOL. Note that a coronary stent is a tube-shaped wire-mesh device (often made of memory alloy) used in the coronary arteries to keep the arteries open for the blood flow to the heart in the treatment of coronary heart disease.
Mechanical Effects of Cardiovascular Drugs and Devices
Published in Michel R. Labrosse, Cardiovascular Mechanics, 2018
A coronary stent is a metal scaffold placed via a delivery catheter into the coronary artery or a saphenous vein graft to maintain the lumen open for blood flow. In the short term, the device increases blood flow through the vessel. Over the long term, the device must heal into the surrounding tissue while maintaining the open lumen of the blood vessel. Stents are typically made of a metal mesh that covers only 7%–20% of the solid vessel wall beneath it. The mesh is constructed of wires that can be open- or closed-cell, coiled, laser-cut, or multilinked. The stent should be flexible enough to conform to tissue anatomy but stiff enough to provide vascular support. As observed with PCI, intimal hyperplasia results from treatment-induced injury and causes rapid restenosis of bare-metal stents in the coronary circulation in approximately 30% of patients within 12 months. Although a significant improvement over unstented PCI, this complication diminished the cost-effectiveness of the procedure. In 2003, the first drug-eluting stent (DES) was approved. The DES is a bare-metal stent that is coated with a drug-imbedded polymer that slowly releases anti-inflammatory agents into the tissue to reduce restenosis.26 Clinical results demonstrated a 90% reduction in restenosis within 12 months, a dramatic improvement in treatment longevity. Some studies have indicated that the DES presents an increased risk of late-stage thrombosis, possibly related to the depletion of the drug coating, accompanied by cessation or reduction of anticoagulant therapy. Many speculated that this complication was not observed in bare-metal stents, because they were coated with a protective layer of endothelial cells and the stent struts were “embedded” into the wall of the artery, thereby becoming an “inside the wall” support. Recommendations for the DES and late-stage thrombosis include extending antiplatelet use to 1 year and improving deployment practices to reduce malapposition. A recent innovation is the resorbable stent, which functions as a DES for the first year but gradually resorbs over time, leaving the vessel free to heal. The device is an absorbable scaffold polylactide with a drug-eluting coating; it is placed via a delivery catheter into the coronary artery or saphenous vein graft to maintain the lumen. The drug coating is intended to inhibit restenosis. The absorbable stent provides mechanical support to the treated artery and a drug agent to prevent restenosis of the treated artery. It then gradually dissolves and is absorbed by the body within approximately 3 years.
Biomimetic materials based on zwitterionic polymers toward human-friendly medical devices
Published in Science and Technology of Advanced Materials, 2022
Most cardiovascular medical devices are used in an environment in which they are in long-term contact with blood. Therefore, it is important to prevent blood coagulation, which is suppressed through the combined use of anticoagulant therapy. A coronary stent is a medical device that utilizes metal strands to patent a narrowed portion of a blood vessel [137]. A coronary stent is an endovascular treatment that is placed at a predetermined site by a catheter attached to a guidewire from the blood vessel of the thigh. When first developed, the metal surface of the strands was exposed (metal-bearing stent). However, with advances in technology, over the years, the surface was gradually coated with polymers (polymer-coated stent), and now, the polymer layer is even incorporated with drugs (drug-eluting stent). The polymer coating layer acts as a reservoir for drugs that prevent thrombus formation immediately after attachment and the thickening of blood vessels.
The optimal structural analysis of cobalt-chromium alloy (L-605) coronary stents
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
Huajie Wang, Xianying Wang, Hongliang Qian, Deda Lou, Mingming Song, Xiaoqian Zhao
The coronary stent is the most commonly used medical device in the intervention treatment of coronary heart disease, with a main function of delivering stents to the stenosis site, and expanding vessels by the stents to ensure the normal flow of blood (MA et al. 2020). Therefore, the mechanical properties of these stents have a direct influence on treatment effects.