Introduction
Coronary arteries are the blood vessels supplying the heart with oxygen-rich blood. Any limitation in the blood flow through these arteries results in malfunctioning of the heart muscles and is known as coronary artery disease or ischemic heart disease. It is often caused by atherosclerosis or the accumulation of cholesterol or plaque (fatty deposits) inside the lining of the coronary arteries, causing a partial or complete blockage in the blood flow. As the blood flow reduces, it can cause chest pain or chest discomfort and may lead to further complications. Initially, it can be managed by medications and certain lifestyle modifications. However, complex cases require surgical intervention. Coronary stenting or coronary angioplasty with a stent is one such surgical procedure performed to widen the artery or maintain the clogged blood vessels open to facilitate better blood flow and improve the functioning of the heart.
What Is a Stent?
A stent is a small tube-shaped mesh that holds open narrowed blood vessels such as coronary arteries (blood vessels that supply oxygen-rich blood to the heart) or other structures. Stents also treat an aneurysm (a bulge in the artery wall) and narrowed lung airways (an airway stent). Stents are made as a mesh using metal, silicone, fabric, or a combination of these materials. Metal mesh is usually preferred for coronary arteries, silicone for airway stents, and fabric or stent grafts are used for large arteries such as the aorta. When a stent is placed into any structure in the body, such as an airway, blood vessel, etc, it is called stenting. It mainly helps to relieve blockages, treats weak or narrowed blood vessels, and prevents various disorders.
What Are the Types of Stents?
There are different types of stents which have different purposes. The materials used to design these stents also depend on the site of insertion in the body. The main types of stents include:
- Coronary Artery Stents: These stents are specifically made for carotid or coronary arteries and inserted into the artery after a balloon angioplasty procedure or percutaneous coronary intervention (PCI).
- Aneurysm Stents: These stents are typically used to treat brain and aortic aneurysms. A stent graft is made of leakproof polyester, and a metal mesh below provides a stable channel for the flow of blood.
- Airway Stents: These are usually silicone and can be molded to a particular shape. They are customized to each patient and are easy to insert and remove.
- Other Stents: Stents may also be used in the bile ducts, known as biliary stents, to maintain bile flow, and urethral stents are inserted into the ureters to help drain urine.
What Are the Indications of a Stent?
Stents are mostly used when the arteries become blocked or narrowed, which is seen in the following conditions:
- Coronary artery disease.
- Peripheral artery disease (accumulation of fatty deposits in the arteries of arms or legs).
- Carotid artery disease (blockage or narrowing of arteries that supply blood to the brain).
- Abdominal aortic aneurysm (enlargement or bulged area in the lower part of the aorta).
- Renal artery stenosis (narrowing in one or both the arteries supplying blood to the kidneys).
Some of the other conditions include:
- Biliary stricture (narrowing of a segment in the bile duct).
- Blocked airways.
- Thoracic aortic aneurysm (bulged area in the upper part of the aorta).
- Blocked or damaged ureter (thin tubular structures that carry urine from the kidneys to the urinary bladder).
How Do Stents Work?
Though stents are recommended for various medical conditions, they are most commonly used to treat coronary artery disease. Angioplasty is a surgical technique that widens the narrowed blood vessels and improves the blood flow to the heart. During coronary angioplasty, a catheter with a deflated balloon is inserted into the blood vessel by a tiny incision in the wrist, arm, or groin. The catheter is monitored by X-ray equipment, and the block is identified. Once the clogged area is recognized, the balloon is inflated, squashing the plaque and opening the arteries. The stent is then placed in the artery to prevent narrowing and keep the artery open. Stenting is a minimally invasive procedure and has a quick recovery. Coronary artery stents are of three main types:
- Bare-metal Stents: These were developed in the mid-1990s and are mesh-like tubular structures made of thin metal without any coatings. Platinum-chromium, cobalt-chromium, and stainless steel were preferred for designing them. These metals are available in tubes, wires, or sheets, which are then fabricated into tubular structures by welding and special locking features. Bare metal stents were mainly used to restore blood flow and prevent loss of function over time. However, the immune system considered this stent a foreign object, and complications such as abnormal tissue overgrowth were observed. Hence, bare metal stents were replaced by drug-eluting stents.
- Drug-eluting stents: These are metal stents coated with medicine, or a medicine-infused polymer coating is applied to the metal stent. The medicine gets released gradually over time and prevents the artery from closing or narrowing again. Some drugs used in these types of stents are Everolimus, Novolimus, Sirolimus, Biolimus, Zotarolimus, etc. Each drug differs in its potency, structure, lipophilicity, and molecular weight. These drugs help reduce the immune response to the stent and prevent the growth of abnormal tissue around the stent. The recent type of coronary stents developed are dual therapy stents, which have drug coating on both sides of the stent. However, blood thinning medications or anticoagulants are prescribed after the procedure to reduce the formation of blood clots.
- Bioabsorbable Stents: These stents, also known as biodegradable stents, are useful for a short period and were developed to overcome the limitations of drug-eluting stents. They are made of polymers or metals like magnesium, iron, or zinc alloy and help maintain the widening or opening of the arteries. They usually dissolve in about two years. However, they are not recommended for elderly people.
What Are the Risks or Side Effects Associated With Stents?
Some of the side effects or risks associated with stents or stenting procedures include:
- Damage to the blood vessels or nerves.
- Bleeding or blood clots at the area of catheter insertion.
- Infection at the insertion site.
- Damage to the heart valve.
- Irregular heartbeat.
- Allergic reactions to the stent material, dye, or the drug used in the procedure.
- Misplacement of the stent.
- Failure of the stent to function
- In-stent restenosis (relapse of blocking or narrowing of the artery due to tissue overgrowth around the stent).
- Serious complications may occur in some rare cases, such as kidney failure, stroke, and heart attack.
Conclusion
Coronary artery disease is when the arteries get blocked with fatty deposits, resulting in a reduced blood supply to the heart muscles. Stenting is a minimally invasive surgical technique that widens the arteries and allows adequate blood supply to the heart. A stent is a tiny mesh-like device inserted into the newly opened artery that helps prevent future narrowing or blockage. Stents also help reduce cardiac symptoms such as shortness of breath and chest pain and improve the functioning of the heart. However, a balanced diet, regular exercise, and a healthy lifestyle are recommended to maintain overall well-being.
