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CT Coronary Angiogram (CTCA)

What is it?


It is an imaging technique that uses Computed Tomography (CT) scanner to obtain images of the heart and coronary arteries. It will be able to give valuable information of the structures of the heart and of the coronary arteries.

How it works


The CTCA scanner takes multiple images of your heart and coronary arteries by rotating the scanner around you while you lie on the table. The scanning time takes only less than a second, but you will need to lie on the scanner table for up to ten minutes. The CTCA scanner will then reconstruct the images into a 3D picture of your heart, and will be able to analyse if you have any significant narrowing or blockages in your coronary arteries.

Why would your doctor choose this investigation (CTCA) over the conventional coronary aniography?


  • CTCA is a non-invasive investigation whereas the conventional coronary angiography is an invasive test which requires hospital admission and involves insertion of tubes (catheters) via a arterial sheath to insert or “engage” the coronary artery, thereby allowing dye (contrast) to be directly injected into the arteries. (see information on coronary angiography). On the contrary, CTCA only involves injection of contrast through an intravenous cannula (plastic needle or drip line).


  • You may still require invasive coronary angiography if there are significant narrowing or blockages in your coronary arteries.

  • What are the risks involved?
    It is generally a very safe procedure. However, there are a few risks involved: Bleeding and bruising around the puncture site (<5%). Allergic reaction to contrast (minimal risk). Major bleeding and bruising (<1%). Injuries to blood vessels at the puncture site, eg. pseudo-aneurysm, dissection etc (<1%). Major bleeding into the abdominal cavity (very rare). Heart attack or need for emergency bypass surgery (very rare). Stroke or mini-stroke (very rare).
  • How do I prepare for the procedure?
    You are required to fast (nothing to eat or drink) for at least 6 hours prior to the procedure. For diabetics: ​ Please do not take your diabetic medications in the morning of your procedure. Please do not take metformin for 48 hours after the procedure.​​​
  • What can I expect when I am transferred to the cardiac catheterization laboratory (cath lab) for the procedure?
    You may occasionally be given a sedative, either orally or through an intravenous line just before the procedure to help you relax. You will, however, still be awake during the procedure. The cath lab is a specialised X-ray suite where your coronary angiogram is performed by your interventional cardiologist, assisted by specialised cardiac scrub nurses. The puncture site (your wrist and /or groin) will be cleaned with an antiseptic solution and thereafter, a sterile drape will be used to cover you.
  • What can I expect during the procedure?
    The catheter will be passed to the coronaries in your heart via arteries in the arm, or via the aorta if the groin approach is taken. If your artery in your arm is considered to be small or tortuous, there is a chance that the groin approach will be taken rather than using the wrist as an access. In this situation, groin approach would be then converted from radial approach. It is generally a painless procedure, however, you may feel some discomfort in your arm while the catheters passes through. You will also notice that the X-ray machines be rotating around you during the procedure. This is to ensure the appropriate coronary images are taken during the study. When your Interventional Cardiologist positions the catheter at the origin of your coronary arteries, contrast (dye) will be injected into your arteries. Occasionally, due to differences in body sizes and shapes, different sized catheters have to be used (and exchanged at the sheath) to be able to position the catheter accurately at the origin of your coronaries. Moving images of Xray will then be taken as the dye “colours” your arteries. Your Interventional Cardiologist will then be able to identify the significant blockages affecting your coronary arteries. The whole procedure usually takes up to 30mins, but may be prolonged due to complexity of locating your coronary arteries. Your Interventional Cardiologist will inject local anaesthetic around the puncture site (wrist or groin). This puncture site is where catheters (long tube) will be inserted via a small tubing (sheath) after a small cut in the skin.
  • What can I expect after the procedure?
    Following the completion of the procedure, The sheath will be removed from your wrist or groin, and firm constant pressure at the puncture site will be applied to avoid bleeding. Occasionally, your Interventional Cardiologist may deploy a special device that will stop the bleeding. Your nurse will also monitor your blood pressure, heart rate and puncture site for bleeding closely. You can normally be discharged after 2 to 6 hours, after being observed in the recovery room. The nurse caring for you will instruct you to rest in bed for up to 4hrs depending on whether the wrist or the groin is used as the puncture site. You are encouraged to make prior arrangements for someone to send you home, especially if you have been given sedatives. Please do not drive for the next 24hrs post procedure if you have been given sedatives. What should I look out for when I reach home? On the night after the procedure, please rest with minimal walking if the groin procedure was done. Use your arm minimally with minimum wrist flexion for the next 24-48hrs if you have a wrist puncture. You are discouraged from lifting heavy weights for 7 days after the procedure. You can remove the plastic bandage dressing the day after the procedure. Drink lots of fluids. Please make an appointment to see either your Cardiologist or General Practitioner 1 week after your procedure to check on your puncture site. Please take note: If you notice that your puncture site (groin or wrist) becomes painful and develops a large lump, you are advised to lie down immediately and apply pressure on the puncture site with the help of someone. Please seek medical attention (calling an ambulance or proceed to nearest hospital) immediately as this could be due to bleeding from your artery.
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