Introduction
Coronary artery disease is a condition in which the coronary artery is narrowed or weakened due to the accumulation of lipids and fats. Placing a cardiovascular stent at the weakened site of the artery is the standard procedure for treating this disease. A cardiovascular stent is a life-saving device that ensures cardiovascular support by maintaining the blood flow to the cardiac muscles. Various generations of cardiovascular stents have been developed to improve patient outcomes. This article gives insight into the types, uses, side effects, and risks of cardiovascular stents.
What Are Cardiovascular Stents?
Cardiovascular stents are small, tubular structures that are complex, hollow, and cylindrically shaped structures comprising connecting elements and a series of struts. It is implanted in the narrowed or blocked site of the coronary arteries to improve the blood flow to the heart. It supports the arterial walls, keeps the artery open, and improves the blood flow to the heart muscles. The functioning of a stent depends on the design of the stent.
Coronary arteries are the blood vessels that supply oxygen-rich blood to the muscles of the heart. Over a period of time, plaque can accumulate in the coronary arteries and limit the blood flow to the heart. This damages the heart muscle and increases the risk of heart attacks. A cardiovascular stent is implanted in the narrowed or blocked site of the coronary artery to improve blood flow and prevent a heart attack.
What Are the Types of Cardiovascular Stents?
Advancements in technology have led to the evolution of cardiovascular stents. A balloon catheter with a fixed wire evolved into bare metal stents, first-generation drug-eluting stents, and second and third-generation drug-eluting stents that are polymer-based and bioresorbable vascular scaffold, which is under development.
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Bare-Metal Stents:
The bare-metal stent was the first cardiovascular stent, introduced in 1986. It is manufactured from corrosion-resistant materials, including cobalt-chromium, stainless steel, platinum-iridium alloys, and tantalum or nitinol. The bare-metal stents had various drawbacks, including acute occlusion and neointimal hyperplasia, chronic inflammatory response, and late-stage thrombosis. The limited biocompatibility of stainless steel also poses problems such as thrombosis formation. Nickel present in nitinol can induce immune responses. It also caused the recurrence of stenosis in the stent due to arterial damage and stent implantation. To overcome these life-threatening events, drug-eluting stents were developed.
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Drug-Eluting Stents:
The first-generation drug-eluting stents were introduced in 2002. The structure of this stent was based on a stainless steel platform, which was coated with a durable polymer that elutes the drug. Drugs with antiproliferative effects, such as sirolimus and paclitaxel, are used. Drug-eluting stents allow localized elution over a period of time. These stents prevent in-stent restenosis. The long-term safety and efficacy are higher compared to the bare-metal stents. It also improves revascularization and reduces the risk of thrombosis. However, the first-generation drug-eluting stents required longer dual antiplatelet therapy, which increases the risk of bleeding compared to bare-metal stents. It also delays arterial healing due to inflammation of the peri-stent tissues that are caused by the polymers used as drug carriers. To overcome these disadvantages, second-generation drug-eluting stents were developed in 2008.
The second-generation drug-eluting devices were modified with improvements in flexibility, deliverability, and strut thickness. Changes were made in the platform, coating, and drug. Other materials like cobalt-chromium and platinum-chromium alloys were used instead of stainless steel to reduce the strut thickness. Drugs such as Zotarolimus, Everolimus, and Novolimus were used. These drugs infuse into the vessel wall and inhibit vascular restenosis, and suppress transplant rejection. However, the long-term durability is not known and poses limitations in terms of adaptive remodeling and abnormal coronary vasomotion. Therefore, extensive research is being conducted to develop non-permanent devices.
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Bioresorbable Stents:
Stents are generally required for a temporary period for their short-term benefits associated with healing and re-endothelialization. However, these stents create various complications in the long term. They cause adverse effects like chronic inflammation, late-stage thrombosis, and restenosis. To overcome these limitations, bioresorbable stents were developed. Biodegradable stents provide support for a temporary period and progressively degrade. Biocompatible and biodegradable polymers are used in bioresorbable stents. They function as alternatives to permanent stents. Magnesium alloys in these stents offer higher elastic and tensile strengths and maintain a uniform degradation. Also, the electronegative charge during degradation provides the antithrombotic effect. However, adverse effects like poor healing, increased scaffold fracture risk, platelet deposition, and poor deliverability have been reported.
What Are the Uses of Cardiovascular Stents?
Cardiovascular stents improve the blood flow to the heart muscles and prevent further damage. It also improves the symptoms such as shortness of breath and chest pain. Stents are used to treat conditions such as coronary heart disease, peripheral artery disease, renal artery stenosis, abdominal aortic aneurysm, and carotid artery disease. It is also used to keep the blocked ureter open, for treating aneurysms, to keep the blocked bile ducts open, and to keep the blocked airways open.
What Are the Side Effects of Cardiovascular Stents?
The common side effects of cardiovascular stents are the formation of blood clots that cause heart attacks, stroke, thromboembolism, and restenosis of the artery. Restenosis is the most common side effect of bare metal stents. Stent thrombosis is common during the first month of stent placement.
What Are the Risks Associated With Cardiovascular Stents?
Cardiovascular stents include the following risks:
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Damage to the coronary artery during stent placement.
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An allergic reaction to the dye used during this procedure.
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Blood clots.
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Bleeding.
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A heart attack.
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Infection in the artery.
Conclusion
Cardiovascular stents are a boon to the treatment of cardiovascular disease. It helps improve the blood flow and keeps the blocked or narrowed coronary artery open. Various types of cardiovascular stents have evolved over time. Biodegradable stents are recently developed stents. Despite various revolutions in cardiovascular stents, complications are still present. To overcome these limitations, extensive research is being carried out to determine the best stent design that is biocompatible and has sustained drug release. Research is being carried out on nanomaterials-based platforms that would serve as drug-releasing systems as well.
