Quick answer. A coronary angiogram (a type of cardiac catheterisation) is a test in which a thin tube (catheter) is passed from an artery in the wrist or groin up to the heart; contrast dye and X-ray images then show the coronary arteries to reveal narrowings or blockages. It is the gold-standard test for coronary artery disease and is used to investigate angina, an abnormal stress test or a heart attack, and to plan before heart surgery. It is usually done while you are awake under local anaesthetic with sedation, often as a day case, and treatment (angioplasty and stenting) can sometimes be done in the same sitting. Risks are generally low.
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A coronary angiogram is one of the most common heart procedures, and knowing what to expect makes it far less daunting – most people are awake, comfortable, and home the same day.
What it is
Cardiac catheterisation is a procedure in which a thin, flexible tube is guided through a blood vessel to the heart. Most often it is done to perform a coronary angiogram – a contrast dye is injected through the catheter and a series of X-ray pictures is taken, so the cardiologist can see whether the heart’s arteries are narrowed or blocked. Because these arteries are too small to show up on an ordinary X-ray, the dye acts as a map, outlining the flow of blood and pinpointing exactly where atherosclerosis (fatty build-up) or a clot is interrupting it. It is the key test for coronary artery disease, and the same catheter route can be used as an emergency treatment during a heart attack.
Why it is done
Your cardiologist may recommend an angiogram to investigate chest pain or angina, to make sense of an abnormal heart test such as a stress test or ECG, or when a heart attack is suspected. It can measure pressures inside the heart chambers and blood vessels, assess how well the heart muscle and valves are working, and map the coronary anatomy before heart surgery such as a bypass. Importantly, the test can be combined with treatment in the same sitting: if a significant narrowing is found, it can often be opened there and then with a balloon and a stent, sparing you a second procedure.
Wrist or groin access
The catheter is inserted through an artery, usually near the wrist (radial) or groin (femoral). Radial (wrist) access is increasingly common and is associated with fewer access-site complications and a faster, more comfortable recovery, because the vessel is easy to press on afterwards. Groin access may still be chosen when the anatomy or the planned treatment calls for it. Your cardiologist selects the site that suits your body and the reason for the test.
How it is done
You typically stay awake throughout. The skin at the wrist or groin is cleaned and numbed with a local anaesthetic – a brief sting, then a sensation of pressure rather than pain – and a sedative may be given to help you relax. A short sheath is placed in the artery, and the catheter is threaded gently up to the heart under X-ray guidance; you cannot feel the catheter moving inside the blood vessels. When the dye is injected you may notice a short warm flush spreading through your body, and occasionally a fluttering heartbeat, both of which pass quickly. You may be asked to hold your breath or cough briefly while pictures are taken. A straightforward diagnostic angiogram usually takes only a short time; it takes longer if treatment such as stenting is added.
Often combined with treatment
If the angiogram shows a significant narrowing, angioplasty and a stent (percutaneous coronary intervention, PCI) can often be performed in the same procedure. Singapore heart centres run catheterisation labs around the clock, so people having an acute heart attack can have the blocked artery opened promptly – the speed of this treatment is one reason emergency angiography saves heart muscle.
Preparing for the procedure
The team will give you clear instructions beforehand. You will usually be asked to fast (no food, and sometimes only sips of water) for a period before the procedure. Ask specifically about your regular medicines: the team will tell you which to take and which to pause, including any blood thinners and diabetes medicines, as some need adjusting around the test. Tell the staff about any allergies, especially to contrast dye, iodine or previous reactions during scans, and about any kidney problems, since the dye is cleared by the kidneys. Mention if you might be pregnant. Because you may have sedation, arrange for a responsible adult to take you home and stay with you, and bring a list of your medicines with you.
What to expect afterwards
Once the catheter is removed, firm pressure is applied to the access site to stop bleeding – a tight band around the wrist, or manual pressure and sometimes a small closure device at the groin. With groin access you will need to lie flat and keep the leg still for a period; with wrist access you can usually sit up sooner. Nurses monitor your heart rate, blood pressure and the access site for bleeding or swelling. Many people go home the same day or the next day, though an overnight stay is more likely if a stent was placed or a heart attack was treated.
Recovery and aftercare
Look after the access site: keep it clean and dry, watch for bleeding or swelling, and follow any advice about the dressing or wristband. It is normal to see some bruising and a small tender lump, which usually settle over days to a few weeks. Avoid heavy lifting, straining and strenuous activity for a short period so the artery can seal – your team will say how long, and which arm or leg to rest. Drink plenty of fluids to help flush the dye through your kidneys. Most people gradually return to normal activities within a few days; if a stent was placed you will be given specific advice on medicines and on when it is safe to drive or return to work.
Risks and complications
A coronary angiogram is generally safe, and for most people the benefit of knowing what is happening in the arteries clearly outweighs the risks. The most common effects are bruising, soreness or a small lump at the access site. Less commonly there can be more troublesome bleeding, a reaction to the contrast dye, or a temporary effect on kidney function, which is why hydration and kidney checks matter. Uncommonly, more serious complications can occur, including damage to the artery, disturbances of heart rhythm, and – rarely – stroke or heart attack. Your cardiologist weighs these risks against the value of the information and discusses them with you before you consent.
Understanding the results
Sometimes the arteries look normal or only mildly narrowed, which is reassuring and may point the search for your symptoms elsewhere. If narrowings are found, the pattern guides treatment: medicines and lifestyle changes for milder disease, angioplasty and a stent for suitable blockages, or bypass surgery when several arteries or key segments are involved. Your cardiologist will explain the pictures, often with a diagram, and agree a plan with you. You can read more about the condition itself in our guide to coronary artery disease and angina, and general heart information is also available on HealthHub.
The non-invasive alternative
A CT coronary angiogram (CT angiography) is a non-invasive, scan-based alternative that can be appropriate for lower-risk patients or to rule out disease, though the invasive catheter angiogram remains the reference standard and allows treatment in the same sitting. Whether you need an invasive angiogram, a CT scan or another test should be decided with your cardiologist based on your symptoms and risk.
When to seek help afterwards
Contact your care team or seek urgent care if, after the procedure, you notice bleeding or a rapidly swelling lump at the access site, or if the arm or leg becomes cold, painful, numb or pale. Redness, spreading warmth, pus or fever may signal infection and should be reviewed. Call 995 for chest pain or breathlessness, or for stroke symptoms such as face drooping, arm weakness or slurred speech – do not wait to see if they pass.
Related heart conditions & procedures
- Aortic stenosis (narrowed valve)
- Heart valve replacement & TAVI
- Aortic dissection
- Carotid artery disease
- Heart block & slow heart rate
- Infective endocarditis
- Rheumatic heart disease
- Pulmonary hypertension
- Heart bypass surgery (CABG)
- Heart valve disease
- Coronary artery disease & angina
- Cardiologists in Singapore
Sources
- NHS — coronary angiography (definition; access; sedation; risks; CT alternative).
- National Heart Centre Singapore (NHCS) — interventional cardiology (coronary angiography and PCI services; round-the-clock catheterisation labs; radial or femoral access).
- National University Heart Centre (NUHCS) — invasive angiogram and non-invasive imaging alternatives; peer-reviewed evidence that radial access carries fewer complications than femoral.