It is usually done to give pictures of the major blood vessels around the heart, particularly the aorta (the main blood vessel which goes from your heart to supply blood to your body), the pulmonary arteries (the blood vessels that take blood from your heart to your lungs), and the coronary arteries (the small blood vessels that supply blood to your heart muscle).

The picture shows the sort of images that are given by a coronary artery CT scan.

Cardiac CT scans are usually done in the hospital, but sometimes they can be done in community radiology practices. The scan is quick – the actual pictures only take a few seconds to acquire.

Before the scan starts, the radiographer will insert an intravenous (iv) line into a vein in your arm, so that they can inject the X-ray contrast dye that is needed to help your blood vessels show up on the scan. Sometimes you may be given a beta-blocker medicine before the scan: this is to slow down your heart rate so that clearer pictures can be taken. 

You lie down on the bed that you can see in the picture. This then moves into the CT machine while the pictures are taken. You will usually need to hold your breath while the pictures are being acquired.

The X-ray contrast dye will be injected automatically just before the pictures are taken. You may feel warm or flushed briefly or have a temporary metallic taste in your mouth when the contrast is injected.

The radiographer controls the scan remotely from the room next door, but although you’re in the room by yourself, the radiographer can talk to you via an intercom.

There is a small risk of allergic reactions to the X-ray contrast dye. These can include itching and skin flushing, or skin rashes or hives. More severe reactions including difficulty breathing or anaphylaxis can occur, but are very rare. There are appropriate medicines available in the CT facility to treat reactions and even resuscitation equipment if this is required.

You’re at greater risk of an allergic reaction to X-ray contrast if you’ve had a previous reaction. Let the medical team know if this is the case. Sometimes you can be given medicines prior to the scan which will reduce the risk of a reaction.

The CT scan uses a small dose of X-ray radiation to produce the pictures. This is important if you are pregnant (or could be pregnant) because of potential effects on your developing baby. Make sure you tell the team if this applies to you.

You will often need to avoid eating for a few hours before the scan. You’ll usually be able to drink water, but you should avoid caffeine (tea, coffee, chocolate) because this can speed up your heart rate. The information that you are given prior to the scan will explain how long you need to avoid eating.

You’ll be required to lie down on the scan table during the exam, so you may want to wear loose, comfortable clothing. You’ll also need to remove any jewelry and other metal items from your body, such as piercings.