What is an angiogram?
A angiogram is a common test for people with possible heart symptoms. Professor Julian Gunn explains the different types of angiogram to Senior Cardiac Nurse Emily Reeve.
Why would I have a coronary angiogram?
You’d usually have an angiogram because you have signs of coronary heart disease (CHD), such as chest pain, and often because other tests, like an electrocardiogram (ECG), have suggested you might have CHD.
CHD is caused by the build-up of fatty deposits in the coronary arteries. This reduces the blood flow to the heart and leads to a number of problems, including angina or in more serious cases a heart attack.
There are around 250,000 coronary angiograms performed every year
Most people are referred by their GP to see a consultant cardiologist. You’d usually have one or two appointments in a cardiology clinic before a coronary angiogram.
A lot of people think the purpose of an angiogram is to find if there is any disease in any of the coronary arteries. However, the tests mentioned above will usually have given the consultant a good idea that you probably have narrowing in one or more arteries. In most cases the purpose of the angiogram is to find out where the blockages are and what to do about them.
When would I have an angiogram?
There are around 250,000 coronary angiograms performed across the UK every year. CT angiograms are less common at the moment, but in the future they will become more common. There are three circumstances where you might have an angiogram:
- Other tests suggest a high likelihood of narrowings in the coronary arteries and you have significant symptoms.
- You have come into hospital with a ‘mild’ heart attack, you have a resting that shows abnormalities, and a blood (troponin) test indicates some heart damage.
- If you’re having a major heart attack, you’d be brought directly to the cardiac catheter lab to have an angiogram as part of an urgent angioplasty procedure. An angiogram and angioplasty can often be performed together if you need urgent treatment. An angioplasty actually widens your artery, using a small inflatable balloon – usually a stent is also put in, which acts as a scaffold and holds open the artery.
What does a conventional coronary angiogram involve?
In the majority of cases, it takes 20–30 minutes and you won’t have to stay in hospital overnight. You are awake, comfortable and lying down in the catheter lab – a room that looks similar to an X-ray room. The cardiologist will put local anaesthetic into an area of your wrist (for the radial artery) or, less commonly, your groin (for the femoral artery). They will slide a very narrow plastic tube up the artery to your heart, then inject contrast dye through the tube. This is a clear liquid that shows up under X-ray. An X-ray picture of your arteries appears on a screen and the X-ray camera is moved around to create a 3D image showing where the narrowings are and how bad they are. The tube is then removed and a plastic cuff is put on the wrist to stop any bleeding.
What does a CT coronary angiogram involve?
This newer, non-invasive procedure involves lying still in a 3D scanner – it’s round and white with a hole, rather like a Polo mint. You will have dye injected through a vein in your arm. You slide into the scanner, which takes a picture by circling very quickly around your body. You need to hold your breath for a couple of seconds and stay very still. It produces a 3D image of the coronary arteries, but the pictures are less detailed than a conventional angiogram. It could be used, for example, if you come into hospital with chest pain but the cause of it isn’t clear – a CT angiogram could rule out CHD. If the CT angiogram showed significant disease, you may then have the conventional angiogram and possibly an angioplasty.
Do I need to do anything to prepare for an angiogram?
For both types of angiogram, you’ll need to have a blood test to check your kidney function – the kidneys need to remove the dye from your body, so it’s important to check they are working well. For a CT angiogram, you may be offered a beta-blocker to control your heart rate.
On the day of the procedure, you don't have to fast
You should have an appointment where the procedure is explained in detail and you’ll be asked to give your consent. On the day of the procedure, you don’t have to fast, and you should usually take all your regular medication.
Will an angiogram hurt?
Neither test should hurt. For the conventional angiogram you’ll have some local anaesthetic injected in your wrist through a tiny needle, and once it’s numb a small incision will be made, in order to insert the catheter. You may be offered a sedative if you are very nervous, and pain relief if you do experience any discomfort, but most patients don’t need it.
Are there any after-effects?
For the CT angiogram, generally no. And for the conventional angiogram, most people have no problems – fewer than one in 1,000 suffer complications. The most common minor problem is a small bruise on your wrist (or groin). The bleeding risk is higher if the procedure is performed through the femoral (groin) artery, rather than the radial (wrist) artery, particularly if you are taking blood-thinning tablets such as warfarin. There is a very small (about one in 3,000) risk of a stroke or short-term symptoms that mimic a stroke. This is more likely if you are frail.
If a number of coronary arteries are blocked or narrowed, you may be referred to a cardiac surgeon
You will usually be encouraged to drink more water after the procedure to flush out the dye, which is particularly important for those with kidney problems.
Should I worry about the risk of radiation?
For either type of angiogram, the amount of radiation used in modern equipment is about equivalent to a couple of holidays in the sun. You are not under the X-ray camera for long at all.
When do I get my angiogram results?
For the coronary angiogram you will get the results straight away. If there is significant narrowing, or if you’ve just had a heart attack, you may have an angioplasty at the same time. If a number of coronary arteries are blocked or narrowed in places, then you may be referred to a cardiac surgeon for bypass surgery.
Often the results of the test will be discussed at a weekly multi-disciplinary team meeting, where cardiologists and surgeons discuss your case and the best treatment. This removes the risk of individual bias. That decision may come through at your next outpatient visit, or within a few days if you are still in hospital.
For a CT scan, it takes time for the images to be processed, so you will get the results at your follow-up appointment.
What are the latest developments in this area?
When I first started performing angiography in the 1980s, it was done with large tubes inserted through the groin. Bleeding and blood vessel damage were more common; a nurse would need to apply pressure afterwards and you’d be in hospital for a night or two. Now catheters are much smaller, they are usually inserted through the artery in the wrist, and the X-ray dose is lower. It can be done in an afternoon and it’s much safer.
The image quality is far better now, due to digital technology
The image quality is far better now, due to digital technology. The amount of narrowing can be measured precisely. In some centres, blood flow in the narrowed areas can be measured directly using an additional pressure wire test, in which a wire with a small sensor at its tip is used to measure blood flow and blood pressure in or beyond the narrowed areas.
In Sheffield, we are working on an exciting development, partly funded by the BHF, to build a computer model of blood flow through the narrowed artery without needing the pressure wire test. This is exciting because any patient having an angiogram could have our software applied to their pictures, and the doctor would instantly know whether that narrowing needed treatment or not. This is being used in CT angiography, but it is needed in conventional angiography for better planning. This could be the next revolution in angiography.
Professor Julian Gunn
- Professor of Interventional Cardiology, Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield.
- Honorary Consultant Cardiologist at Sheffield Teaching Hospitals NHS Foundation Trust.
- Supervisor of BHF-funded research to develop new computer-based tool for doctors to assess which coronary heart disease patients need stents.