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Cardiac CT

Cardiac CT (CTCA)

Cardiac CT (sometimes referred to as computed tomography coronary angiography (CTCA)) uses computed tomography (CT) scanning to take pictures (angiograms) of the coronary arteries of a beating heart. These arteries supply blood to the heart muscle. Cardiac CT allows your doctor to find out if you have narrowing or blockages of the arteries, which may increase the risks of a heart attack.

What happens during Cardiac CT?

Cardiac CT is typically performed in a radiology clinic. 

Your heart rate will be checked using an electrocardiogram (or ECG) machine. About four electrode patches will be placed onto your skin on the front of your chest, so the ECG wires can be attached. If your heart rate is too fast, you may be given certain medication (tablets or intravenously) to lower your heart rate. Lowering your heart rate makes the images clearer and easier to interpret. 

A CT scan will be performed when your heart rate is at a level suitable for scanning. Shortly before the CT scan, nitroglycerin will be sprayed into the back of your mouth to dilate the coronary arteries.

You will be asked to lie on a bed for the images to be taken by the CT scanner.  While you are on the bed, you will be given a rapid intravenous injection of an iodine contrast agent. When the iodine contrast reaches the heart through the veins, the scan is started. The bed slides in and out of the hole in the  scanner while images of your heart are taken. It is important not to move during the scan, as it will affect the quality of the images. You will also be asked to hold your breath for approximately 10–12 seconds each time a scan is taken. At the same time as these images are being taken, your ECG is recorded. 

Once all the scans have been taken (around 20 minutes), you will be taken to a recovery area for observation and the intravenous cannula will be removed before you are allowed to go home. If you have had medication to lower your heart rate, you might be asked to stay until the effects have worn off.

Preparing for Cardiac CT

Detailed instructions for preparation will be given by the radiology practice at the time of booking for a Cardiac CT. It is important that you advise the radiology facility staff when you make the appointment if you have asthma, diabetes, any kidney problems, irregular heart rhythm or have in the past had an allergy to contrast agents used in a radiology procedure or a strong history of allergy to other things (like foods, pollens or dust). 

Each radiology facility may have slightly different requirements before the test. You may be required to fast for 4 hours before test, as a full stomach with the contrast agent may make you feel nauseated. In any event, it is recommended that you do not have any drinks containing caffeine, such as tea, coffee or cola before the procedure, which can raise your heart rate.

You may generally take your usual medications on the morning of the scan, however, if you are taking metformin for diabetes, please check with the radiology practice to ascertain whether you should stop taking it for this test. In the radiology practice, you may be given extra cardiac medications to slow down the heart rate. 

Allow for several hours in the radiology practice if you are having a cardiac CT. Many patients come to the appointment with a companion who can drive them home. For some people, the medication given to lower the heart rate may make them feel a little light headed walking or driving.

What are the risks associated with undertaking cardiac CT?

The risks associated with the cardiac CT procedure may include complications that may arise in the intravenous procedure such as, on some rare occasions, rupture of the vein from the cannula; injection of the contrast agent into the surrounding tissues, bursting the wall of small veins; and injection of air into the vein.

A small number of patients may have mild to severe allergic reaction to the contrast agent, from sneezing, itching, rash and hives, to a drop in blood pressure and soft tissue swelling, which can be life threatening.
Patients with kidney problems might experience worsening of kidney function after the iodinated contrast agent being administered. This usually improves over several days. If impairment of kidney function is severe, the procedure is generally not carried out unless the information provided by the scan is considered to be so valuable that this outweighs the risk of further deterioration in kidney function.

Beta blockers may cause an asthmatic attack for patients with asthma. Nitroglycerin can cause headache and drop in blood pressure.

The procedure would not normally be carried out on pregnant women because of the radiation exposure to the unborn baby.

The information provided on this page is for general information only and does not constitute and should not be relied on as medical or health advice.

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