A drug-eluting stent (DES) is a medical implant consisting of a tube, made of a mesh-like material. It is used to treat atherosclerosis, the narrowing of arteries. It alleviates the symptom both mechanically (by providing a supporting scaffold inside the artery) and pharmacologically (by slowly releasing a pharmaceutical compound). A DES is inserted into a narrowed artery using a delivery catheter usually inserted through a larger artery in the groin or wrist. The stent assembly carries the DES mechanism towards the front of the catheter, and is usually composed of the collapsed stent over a collapsed polymeric balloon mechanism which is inflated to expand the stent once in position. The stent expands and embeds into the occluded artery wall, keeping the artery open, thereby improving blood flow. The mesh design allows for stent expansion and also for new healthy vessel endothelial cells to grow through and around it, securing it in place.
A DES differs from other types of stents in that it keeps a blood vessel open mechanically and also delivers a small amount of a drug directly into the blood vessel wall for a limited period of time. The drug is chemically attached to the wall of the stent. After the stent has been positioned and the clogged vessel reopened, the stent delivers a small amount of the drug into the blood vessel interior wall. This delivery allows time for stent embedding and reduces the chances of the stent interior becoming blocked. Only a small amount of tissue growth inhibiting drug is carried by the stent, just enough to allow time for blood vessel embedding and for it to function mechanically to keep a vessel open.
DESs are commonly used in the treatment of narrowed arteries in the heart (coronary artery disease (CAD)), but also elsewhere in the body, especially the legs (peripheral artery disease). Since coronary stenting became routine following US FDA approval in 1994, it has matured into a primary minimally invasive treatment tool in managing CAD. Coronary artery stenting is inherently tied to percutaneous coronary intervention (PCI) procedures. PCI is a minimally invasive procedure performed via a catheter (not by open-chest surgery), it is the medical procedure used to place a DES in narrowed coronary arteries. PCI procedures are performed by an interventional cardiologist using fluoroscopic imaging techniques to see the location of the required DES placement. PCI uses larger peripheral arteries in the arms or the legs to thread a DES catheter through the arterial system and place the stent in the narrowed coronary artery. Multiple stents may be used depending on the degree of blockage and the number of diseased coronary arteries that need treatment.
The first DES approved for clinical use was the sirolimus-eluting Cypher stent, which received CE marking in Europe in 2002 and US FDA approval in 2003. Paclitaxel-eluting stents followed in 2004. DES were developed to address the high rates of in-stent restenosis (20-40%) seen with earlier bare-metal stents (BMS); DES reduced this rate to approximately 5-10%. Current-generation DES use thinner struts made of cobalt-chromium or platinum-chromium alloys, biocompatible or biodegradable coatings, and limus family drugs such as everolimus and zotarolimus.
Risks of DES placement include stent thrombosis (approximately 0.7% at one year), bleeding, and allergic reactions to contrast agents. An alternative to PCI with DES is coronary artery bypass graft surgery, which may be preferred for patients with complex multi-vessel disease. The use of DES has been accompanied by debate over potential overuse in patients with stable coronary artery disease, where optimal medical therapy alone may provide comparable outcomes.
Design A drug-eluting stent (DES) is a small mesh tube that is placed in the arteries to keep them open in the treatment of vascular disease. The stent slowly releases a drug to block cell proliferation (a biological process of cell growth and division), thus preventing the arterial narrowing (stenosis) that can occur after stent implantation. While such stents can be used in stenotic arteries throughout the body, they are commonly placed in the coronary arteries to treat coronary heart disease. DES products are integrated medical devices and are part of a percutaneous coronary intervention (PCI) delivery system.
A drug-eluting stent is a medical device with several key properties: it is a structural scaffold that physically keeps an artery open to ensure blood flow; the device has specific drug delivery features, and the chosen drug is critical for its effectiveness. The drug, the hallmark component of the device, is selected for its suitability in inhibiting restenosis and its pharmacokinetics, and the materials used in the fabrication of the device are carefully chosen for their biocompatibility and durability in a biological environment; these materials must also withstand the constant motion of the heart's beat and be suitable for future patient imaging using magnetic resonance imaging (MRI) technologies, which employ high magnetic fields.
Other components, such as the catheter, also play significant roles in the device's overall functionality and effectiveness.
DES are typically composed of metal alloys, most commonly stainless steel or cobalt-chromium, but can also be made of other materials such as platinum-chromium or nickel-titanium. The stent may be coated with a polymer to regulate the rate of release of the drugs into the surrounding tissue. There are also polymer-free stents where the drug is directly coated on the stent or contained in reservoirs within the stent.
The design of the stent includes struts, which are thin wire structures that make up the stent frame. The strut thickness can influence the stent's performance, with thinner struts generally being associated with lower restenosis rates and reduced thrombosis risk.
Most DES are balloon-expandable, meaning they are mounted on a balloon catheter and expand when the balloon is inflated. There are also self-expanding stents, which automatically expand when deployed. The first stent, introduced in 1986, was of this type.
The stent tube mesh is initially collapsed onto the catheter—in this collapsed state, it is small enough to be passed through relatively narrow arteries and then expanded in its destination place, pushing firmly against the diseased artery wall.
The pharmaceutical compounds that these stents emit are antiproliferative agents such as sirolimus, everolimus, zotarolimus, paclitaxel and biolimus. These drugs help prevent the arterial narrowing that can occur after stent implantation. These drugs are also used for other purposes, that involve moderating the immune system or treating cancer. They work by inhibiting cell growth. In DES, they are used in small amounts and for a short time, and only in the area where the stent is placed.
There is a distinction between coronary stents and peripheral stents. While both are used to prevent the narrowing of arteries, coronary stents are specifically for the coronary arteries, while peripheral stents are for any other arteries in the body. Peripheral stents are mostly of the bare metal type; some peripheral DES, of the self-expanding type, are used in arteries of the legs.
Bioresorbable DES are made of materials that can be absorbed by the body over time, potentially reducing long-term complications associated with permanent stents.
Uses General background Atherosclerosis is a chronic disease that affects the large and medium-sized arteries. The disease is characterized by the accumulation of calcium, fats (such as cholesterol) and other substances in the innermost layer of the endothelium, a layer of cells that line the interior surface of blood vessels. Atherosclerosis is considered to be the most common form of arteriosclerosis, which refers to the loss of arterial elasticity caused by thickening and stiffening of blood vessels.
Atherosclerosis can begin as early as childhood with the development of small "fatty streaks" within arteries. These streaks are essentially deposits of fat. Over time, these initial lesions grow larger and become thicker, forming atheromas (atherosclerotic plaques).
Drug-eluting stents (DESs) are used in the treatment of atherosclerosis in both coronary interventions and peripheral arterial interventions: In coronary interventions, DESs are used to treat coronary artery disease, which is primarily caused by atherosclerosis. The stents are inserted into narrowed coronary arteries and then expanded to open up the narrowed artery. The drug compound released by the stents suppresses cellular growth in the newly stented area, reducing the potential for blockage within the stent area itself. In peripheral arterial interventions, DESs are used to treat peripheral arterial disease (PAD), particularly peripheral arterial occlusive disease (PAOD) affecting the arteries of the legs.
Stenosis and restenosis Stenosis refers to the narrowing of the blood vessels, which can restrict blood flow to the organs and tissues. This condition is often caused by the buildup of fatty deposits in the arteries, also called atherosclerosis. Stents are inserted into a narrowed artery during a procedure known as angioplasty. The stents help open up the narrowed artery and improve blood flow. However, over time, the treated artery can close up again, which is a condition known as restenosis.
Restenosis, or in-stent restenosis, is a blockage or narrowing that comes back in the portion of the artery previously treated with a stent. Restenosis tends to happen three to six months after the procedure. Restenosis is even more likely to occur if a stent was not used.
When restenosis occurs, another procedure may be needed to correct the problem, such as the placement of a DES that gradually releases a drug that suppresses cellular growth, thereby reducing the potential for blockage developing inside the stent. This therapy significantly reduces the occurrence of adverse events post-stenting.
Coronary interventions In coronary interventions, DESs release medication over a period of approximately 30 to 45 days following implantation, inhibiting the formation of scar tissue within the stent and subsequent re-narrowing of the blood vessel. Multiple stents may be implanted depending on the extent of disease and the number of affected coronary arteries.
Peripheral arterial interventions In peripheral arterial interventions, DESs have shown improved primary patency and reduced target lesion revascularization compared with bare-metal stents. Different types of DESs are available for peripheral use, each with different drug concentrations and varying efficacy.
Clinical indications
PCI and stent placement are considered when someone shows signs of reduced blood flow in the arteries that supply the heart or when tests, such as different types of coronary artery imaging, show a blockage in those arteries.
Symptoms can include: severe, pressure-like chest pain unrelieved by rest; shortness of breath, fatigue, lightheadedness; palpitations; atypical symptoms: nausea, vomiting, indigestion, confusion, back pain. Because the presentation of ischemic chest pain varies considerably among individuals, clinical decisions regarding stent placement rely primarily on imaging findings rather than symptom descriptions alone.
Contraindications A drug-eluting stent is not recommended in some cases as it may do more harm than good. They are not suitable: when individuals have a bleeding tendency; when a coronary artery has no clear and identifiable narrowing;