A stent is a cylindrical metal stent that can be of various sizes, diameters, structures and materials, depending on the intended application. This structure is used to keep a vessel of the human body or a cavity open. Fouad Bouchta, Managing Director of Reacting.ma, a company specialising for 20 years in health, science and medical research, explains the functioning and characteristics of the stent.
How is a stent implanted?
First of all, you need to understand how a stent works. It can be inserted in two ways:
- The stent is dilated by the balloon of the catheter: here the procedure is performed under local anaesthesia during an angioplasty. The practitioner moves the balloon up to the blocked artery in order to crush the atheromatous plaques, and to be able to place the stent ;
- The self-expanding stent: in this case, the stent is compressed in a thin sheath, which is removed once the stent is deployed and in place.
Characteristics of the stent
There are different kinds of materials, namely:
- Metallic, for some bare metal compounds. It is possible to find models in :
- Stainless steel: this is the most widespread model, especially for the balloon method, for its many advantages. Indeed, it offers a good visibility to X-rays, its consistency is both elastic and resistant, and it has a good biocompatibility. However, its low MRI compatibility, lower resistance or risk of injury from vessel wall damage should be noted;
- Cobalt alloy: Cobalt-chromium is the most common of these, for its strength and high radio-opacity. The risk of thrombosis is reduced by the smaller mesh size, but a risk of restenosis remains possible;
- Nickel-titanium alloy, also called nitinol: it is widely used for carotid and self-expanding stents. The diameter is often larger than the vessel in which it is installed, so as to have a constant pressure. It is prized for its elasticity and resistance to corrosion, but one must be aware of its opacity to X-rays.
- Coated: Some models have a metallic skeleton, with a passive (gold, carbon, polymer or ceramic coating) or active (drugs such as heparin or thrombomodulin) coating.
In addition to these main models, there are also drug-eluting or bioresorbable stents, which are known to be particularly biocompatible. Some models are made of a magnesium alloy (with little magnesium elution) or iron, others of polymers (PLLA). Finally, radioactive stents are more rarely available. These models are intended for brachytherapy. They can be bombarded by charged particles (and in case transforming stainless steel atoms into radioisotopes) or have radioisotopes implanted in the structure.