How do stents work?
These tiny devices keep arteries open and can save lives. Senior Cardiac Nurse Emily McGrath hears how stents work from Professor Simon Redwood.
A stent being inserted using a balloon and a catheter
What do stents do?
These tiny but vital devices can hold the artery open in an area where you have a narrowing. They are inserted in an angioplasty procedure, either as an emergency to treat a heart attack, or in a planned way to widen an artery that is being narrowed by a build-up of fatty plaque.
If the artery is stretched open with just a balloon (angioplasty without a stent), the artery may ‘recoil’ and narrow again afterwards. The risk of re-narrowing is around 30 per cent, whereas when a stent is used this reduces to around 10–15 per cent. If that stent is a ‘drug-eluting’ stent, the risk is further reduced to around 2–3 per cent.
Stents can treat heart attacks and angina when used in your coronary arteries
Nowadays, stents are used in all angioplasty procedures, unless the blood vessel is too small or too large to put a stent in, or the patient has an allergy to the material in the stent (which is very rare).
Stents can treat heart attacks and angina when used in your coronary arteries. They can also be used in the legs (to treat peripheral arterial disease) and occasionally in the neck (if you have a narrowing of the carotid artery that supplies your brain) or the renal arteries, which supply the kidneys.
What do stents look like?
Stents are cylindrical in shape, and they are made from a very fine metal mesh.
How big is a stent?
The most common stents are around 15–20mm in length, but can vary from 8–48mm, and are 2–5mm in diameter.
How are stents inserted?
A long hollow tube (catheter) is inserted from the wrist or the groin and guided (using X-rays) all the way to the narrowed artery. A very fine wire is fed through the catheter and into the narrowing. Over that wire, a balloon is inserted with a ‘squashed-down’ stent on it.
Once the cardiologist is happy that it is in the right position, the balloon is inflated, widening the narrowed part of the artery and expanding the stent to fit the artery wall. Then the catheter, balloon and wire are removed, leaving the stent in place. The procedure usually takes 30–60 minutes.
What is a stent made of?
It is made from metal such as stainless steel, platinum-chromium or cobalt-chromium. It may also have a coating called a polymer and, in most cases, a coating of a drug to stop scar tissue growing between the gaps in the stent (as this could cause re-narrowing). These are called ‘drug-eluting stents’ and are used around 95 per cent of the time because the long-term results are much better.
Will it hurt?
It’s generally painless. You’ll have local anaesthetic injected before the catheter is put in. The inside of the artery doesn’t have nerve endings, so you shouldn’t feel anything there.
Some people experience mild chest pain when the balloon is inflated. You’ll be awake throughout and lying down. Some patients can have sedation but most don’t need this.
Is a stent put in through the groin or through the wrist?
The wrist is used the majority of the time – there is a lower risk of bleeding from the insertion site. The groin allows for larger catheters and can sometimes give easier access, so it is the preferred choice for complicated procedures.
How long will a stent last?
It is permanent. There is just a 2–3 per cent risk of narrowing coming back, and if that happens it is usually within 6–9 months. If it does, it can potentially be treated with another stent. You might experience narrowings in other arteries, which again can usually be treated with further stents.
Taking your prescribed medications and making lifestyle changes (especially stopping smoking, treating diabetes and high blood pressure, and lowering your cholesterol) can reduce the risk of needing more stents.
What are the risks of stents?
It’s common to get a little bit of bruising where the tube went in – this usually clears within a couple of weeks. Bleeding is uncommon, but easily resolved by applying pressure to the site.
The risk of bleeding is lower in the wrist than in the groin because the artery sits just under the skin, so putting pressure on the site is more effective at stopping the bleeding quickly.
The risk of a major complication is less than one in 100.
The risk of a major complication is less than one in 100. This includes splitting the walls of the artery when the balloon is inflated, known as a dissection, which would be treated quickly with further stents.
The procedure itself can cause a blood clot to dislodge resulting in a heart attack, but the risk of a major complication like this is about one in 500 – in other words, extremely rare.
What is recovery like?
For a planned angioplasty, the heart generally recovers right away. You will be up and walking around immediately after the procedure if the wrist is used. You will have to lie down for a few hours if the groin is used and will stay in the ward for 4–6 hours to check there is no bleeding from the insertion site.
The following day you should be feeling fine, but you do need to be careful with heavy lifting for a few days and take it easy for a couple of weeks. If your stent is put in to treat a heart attack, then recovery may take a little longer, depending on the severity of the heart attack.
DVLA rules state that you shouldn’t drive for a week after having an angioplasty and stent, or four weeks if the procedure wasn’t successful.
Are there any side effects of putting in stents?
Having a foreign body in contact with your blood can lead to a small risk of blood clots forming on the stent. This risk is around one in 50 in the first year after the stent, but medication will reduce this.
Aspirin is usually prescribed for life and clopidogrel is usually prescribed for 3-12 months after the procedure.
We prescribe aspirin and a second antiplatelet drug (usually clopidogrel, but occasionally prasugrel or ticagrelor) that acts with the aspirin to stop a clot forming.
Aspirin is usually prescribed for life and clopidogrel is usually prescribed for 3–12 months after the procedure. During that period the inner lining of the artery grows over the stent so it is incorporated into the blood vessel wall, which means that the risk of blood clots is lower.
Am I at risk of an allergic reaction to the stent? Or could my body reject it?
Allergic reactions are almost unheard of, as the metals that stents are made from rarely cause allergies. Because the stent is not made of living tissue, you don’t get the problem of rejection.
Is there a difference between an NHS and a private stent?
Not any more. The newer stents used to be less available in the NHS, but we now routinely use drug-eluting stents both in the NHS and privately.
Professor Simon Redwood
- Professor of Interventional Cardiology and Honorary Consultant Cardiologist at St Thomas’ Hospital, London
- More than 20 years’ experience performing angioplasty procedures
- President of the British Cardiovascular Intervention Society from 2012 to 2016
- Author of over 200 research publications
- His current BHF-funded research includes looking at whether people who have a cardiac arrest following a heart attack should be treated in specialist centres