The bare metal stent is a tubular medical device with latticed mesh walls. It is surgically inserted into peripheral or coronary arteries to expand their diameter and improve blood flow when cardiovascular disease has caused narrowing of the vessel. They are made from various metals and are designed to improve on the balloon angioplasty procedure that has a higher rate of complications. Patients who have a bare metal stent implanted may experience restenosis — a renewed narrowing of the blood vessel following implantation. Blood clots, or thrombosis, and the formation of lesions are two other complications that can occur.
Metals capable of being machined to be flexible enough to conform to the artery wall's shape are used to make these stents. These materials include stainless steel, nitinol, and cobalt chromium. The stents range in diameter from about 2 mm to 4 mm and and are typically between 8 mm and 38 mm long, depending on the length of the arterial blockage. The walls of the stent, which exert expansion pressure on the surrounding artery, are made with various strut configurations including coil, serpentine, and corrugated designs. The thinnest struts have a lower restenosis rate and are sometimes lined with heparin, carbon, or platinum to reduce the risk of thrombosis.
The procedure for implanting a bare metal stent involves the use of a guide wire and a guiding catheter together with a balloon-tipped catheter with the stent attached. The guiding catheter is inserted into the femoral artery and positioned at the point of arterial blockage. The guide wire is then inserted into the catheter and the balloon-tipped catheter with its stent is fed through it to the blockage. The balloon is inflated to dilate the blood vessel and then removed, leaving the bare metal stent in place pressing against the artery walls. During recovery, the artery wall tissue grows into the latticed wall of the stent.
To combat restenosis, the patient may be given brachytherapy — a radiation dose delivered via a catheter that reduces thickening and scarring of the artery wall tissue. Anti-coagulant drugs are also given for this purpose. Experiments with anti-coagulants have led to the development of drug-eluting stents. Designed similarly to a bare metal stent, they slowly release chemicals that inhibit cellular growth and thus reduce restenosis. They have been statistically shown to lower rates of serious complications such as myocardial infarction.
