Medical procedures for blocked arteries often include the insertion of a metallic implant called a stent. A network of interlocking metal components called struts typically make up a stent, and enable it to unfold once surgeons guide it into a blocked blood vessel. It can be made of stainless steel, but the chromium cobalt stent is generally stronger and tolerant of motion that can occur in arteries that move or bend, such as near the kidneys. Various stents can be different sizes and some are up to 0.4 inches (10 millimeters) wide or larger, while they can be about 2.4 inches long (about 60 millimeters) long.
The struts of a chromium cobalt stent are typically thinner than those of a stainless steel one. These parts are often rounded without sharp edges, making a surgical procedure for putting stents in complex blood vessels such as the iliac arteries, in the pelvis, generally safer. Like many types of stents, it is threaded through arteries to get to the location it is needed, and then expanded with a balloon-like device.
A chromium cobalt stent is usually tolerant of fatigue that can result from forces inside a blood vessel. Motion often occurs in arteries in the pelvic area as well as those around the kidneys, particularly from respiration. Blood flow can cause pulsations in blood vessels too; any kind of motion can lead to damage to stents over time, which often requires additional surgeries or bypass of the vessel if there is significant damage to it. Damage to stents sometimes happens because of loading forces during manufacturing, which can crimp the metal, as well as from expansion during a surgical procedure.
The longer a chromium cobalt stent is, generally the more stress it is exposed to. Clinical studies have shown that this type is typically more tolerant of common stress factors, and fewer people require additional operations to open up blood vessels. Computer simulations as well as finite element analysis are often used to assess the fatigue resistance and structural integrity of a chromium cobalt stent.
Simulating motions that typically occur can help identify which part of the device is most vulnerable. The chromium cobalt stent has been found to generally tolerate respiration-induced bending over the long-term, based on study data. This same material can be used with drug eluting stents, which release medication to prevent additional blockages in an artery. Most stents, based on studies, are implanted without serious complications, and depending on the material, can last for several years without being damaged.