What is a Stent

Introduction: What is a Stent?

A stent is a tiny tube like structure that is used in treating blocked blood vessels of the heart. It helps in keeping your coronary blood vessels open, which supply oxygen-rich blood to the muscles of the heart. Thus the heart in turn is able to function properly and pump blood to the rest of the body effectively. Majority of the stents are composed out of metal and are permanent in nature. However some special categories of stents are also there now which dissolve overtime once their job is done. Most modern stent have a coating of a drug on their surface which helps in better long term clinical outcomes for the patients by preventing any rapid restenosis (the blockage reappearing) and associated complications.

Why a stent is required?

With age, some blood vessels of the heart tend to develop plaque – a combination of fat, calcium, fibrous tissues etc. These start when the fine inner lining of the blood vessels begin to get damaged. Eventually these slowly growing plaques lead to blockage in the artery, preventing free flow of blood. This is coronary artery disease, a category of heart disease that is becoming increasingly common in India and around the world. In some cases, this disease can eventually lead to chest pain, breathlessness and even cause a myocardial infarction or a heart attack (when the blood flow to a part of the heart stops completely, causing the heart muscles there to die). If a patient is diagnosed with such coronary artery disease, a stent is often used by an Interventional Cardiologist in a minimally invasive procedure known as Angioplasty to clear the blockage, restore blood flow, save the patient’s life and help him or her to recover to a near-normal life. It is therefore no exaggeration to say that a stent is a life-saving medical device.

Is Angioplasty the same as Stent Implantation?

Angioplasty may be performed with or without stent placement. Sometimes, just a balloon inflation may be chosen by the doctor to address the artery blockage issue. If the stent has to be deployed, this first step of balloon inflation is almost always done, followed by the actual deployment. Thus stent implantation is a common (though not mandatory) part of an angioplasty procedure.

Process of stent implantation

• Your doctor will first make a small cut in a blood vessel located in your groin, arm or neck, through which the stent will eventually be inserted into your body.
• He/she then inserts a small tube known as a catheter through the vessel and guides under fluoroscopy to the coronary artery which is clogged by plaque. The tube contains a tiny balloon at its end that your doctor will inflate at the precise location of the blockage. This process will radially push the blockage outward, and thus widen you artery to restore the blood flow to the portion of the heart beyond the blockage site.
• A similar catheter, but this time with a collapsed stent mounted on top the balloon, will then be guided to the same location in the coronary artery.
• The stent will then be deployed by inflating the underlying balloon, which in turn will make the stent expand radially outwards. Once expanded and deployed, the stent holds its hollow tubular shape, and does not collapse back.
• Once the stent has been optimally deployed, its underlying balloon and other associated devices will be taken out. The stent will keep the artery open to keep the usual blood flow running. This whole process may be repeated for any additional blockages seen.
• The entire process of the angioplasty is estimated to last only an hour or so, depending on how many stents are needed. Usually, you will be required to stay in the hospital for a night for observation of any adverse events.
• Risks may include: 1) Hemorrhage at the spot of tube insertion. 2) Blood vessel damage at the time of insertion. 3) Infection. 4) Arrhythmia. 5) In rare cases (1-2%), people implanted with a stent, may develop a clot at the site of stent placement, increasing the risk of a heart attack or stroke. This risk is maximum during the first couple of months post procedure. Hence, your doctor will recommend you to take aspirin or any other blood thinners to prevent clot formation.

Benefits of angioplasty

• Minimally invasive procedure through a very small incision.
• Immediately relieves/decreases symptoms of heart disease.
• Reduces the risk of heart attack or stroke in future.
• Faster healing and quicker recovery.
• Avoids a very strenuous and highly invasive operation like a CABG (bypass surgery)

Are stents really effective at long term in reducing the chance of another heart attack?

A stenting procedure addresses the blockage and thus the risk of a heart attack from that blockage is certainly reduced. However patients must also note the importance of regular medicine intake and lifestyle modifications needed as vital components in reducing the risk of a heart attack even after stent implantation.

How long does a stent last for?

Most stents currently are metallic structures, and therefore permanently remains in the body. It is designed to maintain the lumen of the blood vessel patent, and in vast majority of cases, they cause no further issues at their deployed sites. In some rare cases, there may develop stenosis of blockage in or around a stent, requiring either another angioplasty or a bypass surgery.

Continued research and development has produced some advance new unconventional stents that are absorbable (called Bioresorbable Scaffolds or BRS), which dissolve after a few years. They have very specific uses depending on the clinical need of particular patients.

What are the different types of conventional stents?

There are two primary types of stents:

1) Bare Metal Stents (BMS) : BMS, the older generation stents, give support to the blood vessel to aid in keeping it open post angioplasty. They do not have anything on their surface, just the metallic tubular frame.

2) Drug-eluting Stents (DES).  On the other hand, A DES is a BMS coated with a unique drug coating added for reducing risk of re-blocking of treated arteries. In a DES, the drug gradually gets released from the drug-polymer coating overtime, preventing the reformation of blockages during the initial risk period after angioplasty. The stents are coated with a specialized polymer in case of DES, which encompasses and preserves a drug, capable of preventing uncontrolled cell growth, throughout the stent placement procedure. Once the stent is placed, the polymer aids in regulating the drug release into the blood vessel walls. In short, the polymer for DES is designed to allow a steady and specific drug release from the stent’s surface into the artery walls. In this case, two broad types of polymers exist for use:

• Permanent Polymer: In case of permanent polymer coated DES, the polymer always remains on the stent, even after the entire drug is released.
• Bioabsorbable Polymer: Contrary to the above type, the polymer slowly begins to degrade as the drug release commences in this stent type. This step aids better wound healing through the elimination of prolonged polymer exposure.

The doctor may select a BMS or a DES based on the individual requirements of each patient and case parameters. Each stent type carries its intrinsic merits and demerits which are generally debated well in advance with the doctor. For example, A DES cannot be preferred in the conditions listed below: 1) Allergy to the drug, the polymer or metal (stainless steel, platinum, chromium, cobalt, etc.) composition in the stent. 2) Hypersensitivity to the drugs given to prevent blood clotting. 3) A blockage that disallows proper stent placement. 4) The doctor is of the opinion that the patient is not suitable for placement of stent due to an underlying medical condition.

Harms/Risks of Stenting

• You may get an allergic reaction to one or more component of the stent.
• Angioplasty can lead to hemorrhage, blood vessel damage or even heart damage, or arrhythmia.
• Rarely, some potential complications such as heart attack, stroke or renal failure can also occur.
• A scar tissue formation can happen inside your stent post stenting procedure necessitating another procedure for removing it.
• Stenting also carries a risk of blood clot formation which needs medicines for prevention.
• It cannot ultimately cure your CAD. You have to continue managing your contributing risk factors for CAD such as hypertension, obesity, diabetes or high cholesterol to prevent a future event.

It is important to remember that while it is widely used as treatment for CAD, stent placement is nonetheless a complex procedure, and is associated with complications like any other medical procedure. Your doctor must therefore be thoroughly consulted before such a procedure is undertaken.

What precautions should a heart patient take after stent implantation?

A stent cannot cure your heart disease. It may save you at the critical moment by restoring your blood flow, but it cannot prevent another such event in the future. However, you can take care of yourself and decrease the risk of requiring more of such stents in future by following the heart healthy steps given below:

• Immediately after an Angioplasty stent replacement
  • In case your catheter was inserted through the artery in your groin, you will be needed to lie straight without bent legs, as advised by the nurses and doctors taking care of you.
  • Wait for your nurse to advise you regarding when you could get out of the bed.
  • If your catheter was inserted through the arm, your doctor will place a specialized bandage to ensure proper healing. This must be cared for.
  • Inform your doctor immediately, if you experience chest pain, swelling or pain at the insertion site or bleeding.
  • You will be required to take certain medicines to reduce the chances of blood clot formation.
• Precautions during Recovery:
  • Consult your doctor on when you can return to normal activities like walking, driving, climbing stairs etc.
  • Avoid lifting heavy objects (more than 5 kg) preferably until 1 week after procedure or as advised by the doctors.
  • Once you have the green signal from the doctor, performing regular exercises will aid to speed up your recovery and even after complete recovery, regular physical activity is termed good for heart health with a heart healthy diet.
• General Precautions:
  • Gradually resume your routine activities. Ease into it, strictly as per your doctor’s guidance.
  • You need to regularly take your prescribed medicines as recommended by your doctor, depending on your condition.
  • Adopt a heart healthy diet plan: even minor modifications in your dietary habits can make a huge difference in the health of your heart. You can initiate with the following basic steps, but first consult with your doctor to build up a diet plan that is best suited for your condition:
  • Consume foods that contain more of whole grains.
  • Eat more quantities and varieties of fruits and vegetables.
  • Reduce salt and sugar intake.
  • Also cut down on the consumption of fatty foods that have, rich in high levels of LDL, trans-fats and saturated fats.
  • Encourage inclusion of good fats in your diet (MUFA, PUFA). For easier identification, good fats are substances which remain in liquid form at room temperature.
  • Fish and lean meat are good options for individuals taking non-vegetarian food.
  • Avoid consumption of red meat.
• Continue your exercise regimen and remain physically fit and active as per guidance.
• Stop smoking
• Maintain a healthy weight.
• Try reducing stress.
• Regularly consult your doctor for periodic check-ups.