ABOUT CORONARY STENTS
About coronary stents….
Coronary stents have been around for about 3 decades.
The purpose of this article is to provide answers to questions frequently asked by patients and their family members.
The first procedure to improve blockages in coronary arteries was performed in the late 1970s. It was called balloon angioplasty.
Basically, a tiny long tube with a cylinder-shaped inflatable balloon at its extremity, called a catheter, was inserted through the groin and brought to the narrowed heart vessel under X-ray.
The balloon was then inflated to stretch and expand the blockage to improve the blood flow.
The balloon catheter was then deflated and pulled back out of the body.
Problems related to coronary angioplasty by balloon only
Although this procedure was revolutionary, it had its limitations.
Sometimes, the balloon inflation caused a severe tear of the artery wall and urgent bypass surgery to repair the tear and restore flow was necessary.
The other problem was the need to repeat the procedure after a few months in about 30-40% of the cases.
Because there was nothing to keep the vessel wall expanded, the artery was getting narrowed again, either because of recoil or because of scar tissue formation at the site of dilatation.
The addition of a coronary stent to the procedure
To address those limitations, metal stents were developed.
Stents were mounted and crimped on balloon catheters and advanced into blood vessels after the artery was prepped with balloon angioplasty. They were expanded by balloon inflation until they were against the wall of the vessel. The balloon catheter was then deflated and pulled back from the body and the stent was deployed at the site of the blockage, creating a permanent scaffold to hold the artery walls.
Coronary stents became widely used in clinical practice in the early 90’s.
Type and composition of stents
Most coronary stents used today have a metallic structure. They are either made of stainless steel or various alloys of iron, platinum, chromium, cobalt, nickel and titanium.
Bioabsorbable vascular scaffolds
A minority of coronary stents used in clinical practice are made of a special polymer that eventually dissolves into the body over time. They are called bioabsorbable vascular scaffolds (BVS).
This type of stent is still under development. Although the initial clinical studies appeared very promising, the long-term results of BVS were not as good as expected.
Most metallic stents used in practice are deployed using balloon catheters. They are called balloon expandable. Some stents are self expanding. They are made of nitinol (an alloy of nickel and titanium) and they are kept compressed on the catheter by a tiny retractable sleeve. When the sleeve is pulled back, the stent expands against the vessel wall. This type of stent is most commonly used in peripheral angioplasty (in the arteries of the legs for example).
The very first stents
The first stents to get approved for clinical use were made of stainless steel. They are called bare metal stents.
Although they were very useful to repair acute tears following balloon angioplasty, they were not that great to prevent the risk of re-narrowing after a few months.
The human body was reacting to the presence of those foreign objects and scar tissue was forming inside the stents, creating a new blockage called restenosis.
In about 25% of the cases, the blockage was severe enough to require another procedure within 6 months.
Development of drug-eluting stents
The problem of stent restenosis led to the development of new technologies to counteract scar tissue formation.
These are called drug-eluting stents. Basically, a drug-eluting stent is coated with a polymer that is loaded with an active drug.
The drug is released over a period of a few weeks to control the healing process.
Drug-eluting stents have reduced the risk of restenosis to less than 10%.
Chest pains during stent procedure
During a stent insertion procedure, chest discomfort is not unusual.
When the stent is expanded by the balloon catheter, the blood circulation in the treated vessel is temporarily interrupted for a few seconds. The stent deployment itself can cause some discomfort by stretching the walls of the artery and stimulating some nerve endings.
Finally, when a stent is inserted into a main artery, some side branches present in this section of the vessel where the stent is being employed may get pinched by the stent struts. It is usually a benign consequence of stenting.
Medication after stent placement
After stent placement, and heating process takes place and ultimately the stent struts are covered by the patient’s own cells. In the meantime, there is a risk of clot formation when the circulating blood gets in contact with the surface of the stent.
Possible stent thrombosis
A blood clot could form suddenly, could cause a complete blockage and a heart attack.
This complication could be fatal.
In order to prevent this, patients must take blood thinners after a stent procedure to maintain good blood flow inside the stent.
Two antiplatelet drugs to take
Patients have to take 2 types of drugs to hinder the effect of platelets.
The first one is aspirin, which usually must be taken indefinitely.
The other one is either clopidogrel (Plavix), prasugrel (Effient), or ticagrelor (Brilinta). They are usually prescribed for at least 1 and up to 12 months.
Stents are safe
Complications following stent placement are relatively rare.
There are basically 2 types of complications that may be encountered after stent placement:
- Stent thrombosis (acute blood clot formation)
- Stent restenosis (progressive formation of scar tissue inside the stent)
Stent thrombosis is a serious complication. Most of the stent thrombosis occurs within the first 30 days after the procedure.
In general, clinical practice, the expected rate of early stent thrombosis is about 1%, and beyond 30 days is 0.2%–0.6% per year.
Before the advent of drug-eluting stents, restenosis by scar tissue occurred in more than 25% of patients within the first 6 months of the procedure. This rate has been dramatically reduced to less than 10%.
Repair by stents versus by bypass surgery
In many cases, stenting is a better, simpler, safer and less invasive treatment than open-heart surgery.
Still today, research is being done to verify the reliability of multi-stent repair versus bypass surgery.
Stents are permanent
Once deployed, stents stay inside the vessel permanently. They don’t need to be removed. They cannot be removed.
There is no rejection by the body.
Stents don’t move or migrate
Stents are stretched and expanded against the vessel walls and the eventually get covered by the patient’s own cells.
Stents are chosen according to the vessel size and once they are properly deployed, they cannot be dislodged.
Stents are safely anchored against the vessel wall. Patients can resume their physical activities safely.
Stents don’t collapse
Coronary stents are place inside arteries on the surface of the heart, inside the chest. They cannot be compressed, and they don’t spontaneously collapse.
However, as stated before, they can get acutely blocked by a blood clot or progressively by scar tissue formation.
Stents and medical imaging
Stents do not interfere with nuclear scans.
It is safe to have x-rays or CT scans with coronary stents.
If you require magnetic resonance imaging (MRI), tell the MRI technician that you have an implanted coronary stent.
Patients with all commercially available coronary artery stents can undergo MRI immediately after placement.
It was originally thought that a period of 6 weeks or longer after implantation was necessary, but it has been refuted since there are no known coronary artery stents made from ferromagnetic metallic materials (materials such as iron that form permanent magnets, or are attracted to magnets)
Stents and travel
It is safe to travel after a successful stent procedure.
Coronary stents will not trigger metal detector alarms in airports and you can walk through them safely.
Stents and diet
Your diet has little or no effect on the healing process of the stent itself.
However, your healthcare team may recommend changes to your diet to help reduce your risk of future cardiac events or the risk of coronary artery disease progression.
Recurrent chest pain after a stent procedure
Stents are not perfect. It is possible to have chest pain again, either due to a new blockage in the vessel area treated with the stent or due to a new blockage at another place in your coronary arteries.
Scar tissue may form in the area of your stent. Depending on the severity, this can cause your artery to narrow again over a period of months. If it happens, another stent inserted and expanded inside the first one can often solve the problem.
In some cases, coronary artery bypass surgery may be needed.
There is no sure way to prevent a recurrence of chest pain, but the risk can be reduced through exercise, quitting smoking and eating a healthy diet.
Stents do not cure coronary artery disease
Unfortunately, nothing cures coronary artery disease.
Stenting is not a substitute for medication or for changes in lifestyle (such as exercising more, quitting smoking or having a healthier diet). Both medications and lifestyle changes have been shown to benefit patients.
For patients with stable coronary artery disease, stenting is one tool in the cardiologist’s toolbox.
Stents can save lives
Death from heart attack has been remarkably reduced over the last 30 years.
Before the era of angioplasty, a quarter of patients with heart attack died. Modern angioplasty and stenting has reduced this rate to 5%.
Angioplasty done quickly in myocardial infarction
Stenting has indisputably become the gold standard of care for patients having a heart attack.
Heart attacks are caused by a blocked artery that prevents blood from flowing to the heart. Angioplasty and stenting can restore the blood circulation promptly in the blocked artery.
We often say, “time is muscle.” The longer it takes to treat a patient who is suffering a heart attack, the more damage that the heart muscle may suffer, and the patient may even die.
Stents can also improve the quality of life
Stenting can be appropriate for patients with severe angina (chest pain caused by artery blockage), patients who not respond to medications or who develop side effects.
In that setting, stenting does not save lives but can contribute to improve the quality of life.