An endovascular stent graft is a meshed metal tube inserted in a section of a blood vessel that has developed a pathology, such as abnormal constriction resulting reduction in blood flow. The hollow stent can be expanded to the vessel’s proper diameter. In time, the inner wall of the blood vessel grows to envelope the stent, which becomes a permanent support structure. The stent is surgically guided into place by a radiologist, who injects the circulatory system with a dye visible to x-ray and other radio imaging scans.
There are several types of stents made of different materials for different medical applications. The most common endovascular stent is a thin tube made of bare metal wires woven together in such a way that the tube’s diameter can be stretched. Modern stents are often drug eluting, slowly releasing medication that reduces tissue damage at the site of the stent. The stent is introduced through a large blood vessel such as the femoral artery in the leg. Attached to the tip of a long, flexible instrument called a catheter, it is threaded through the body’s network of blood vessels with the aid of radiological imaging to the precise location for vascular therapy.
Although some surgical stents are temporary measures and eventually removed, an endovascular stent graft is meant to be permanent. It is designed to graft with, and become part of, the inner lining of a blood vessel. When the stent is expanded to fill the diameter of the blood vessel, its wire mesh spreads apart into a lattice which allows regenerative endothelial tissue to fill its spaces. Within a few weeks, the stent becomes a semi-flexible structural scaffold embedded within the inner wall of the blood vessel.
An endovascular stent graft can be used to strengthen the walls of a blood vessel that has weakened, a condition called an aneurysm. It is normally used with a surgical procedure called a balloon angioplasty. The stent is fitted like a sleeve onto a slender, inflatable balloon at the end of a catheter. When the radiologist has positioned the catheter, the balloon is inflated, forcing the stent to expand to the correct, normal diameter of the blood vessel. With the stent in place, the balloon is deflated and the catheter is removed.
The most common purpose of an endovascular stent graft is to enlarge a blood vessel that has become constricted, a condition called stenosis. One common cause of this is excessive cholesterol in the blood that hardens into plaque. If the blocked vessel is the coronary artery, which supplies oxygen and nutrients to the heart muscles, stenting may make up to 70 percent of corrective surgery. It is a well-practiced procedure.
Since the inflation pressure of a balloon catheter can be precisely controlled, catastrophic injury to the blood vessel during surgery is a rare complication from an endovascular stent graft procedure. The most common post-operative recovery concern is restenosis, when the blood vessel reacts to the presence of a foreign object and reverts to a constricted condition. It can be caused by fibrosis, or scarring of the vessel wall, and more seriously, thrombosis, or the development of blood clots. Drug-eluting stents have decreased this possibility, but it is imperative to adhere to a supervising physician’s prescription regimen of blood thinning and anti-blood clotting medication.
