A computed tomography coronary angiogram, often called a CT coronary angiogram, is a test that can help determine whether the arteries that supply blood to the heart muscle are diseased or narrowed. It is sometimes called a Coronary Computed Tomography Angiogram (CCTA) or a ‘1-minute’ angiogram.
Here we take a look at this condition in a little more detail.[toc]
What is a CT coronary angiogram?
This is a test where pictures of the heart arteries are taken by injecting a dye into the arteries and taking a photo with a CT scanning machine. It is a non-invasive way of determining the state of the blood supply to the heart muscle. It can help determine if there is build up of plaque in the arteries around the heart.
A CT scanner is a big machine that is used to image different parts of the body. When creating an image of the heart, it does so by taking pictures at different levels of the heart muscle. CT scanners that are used for this procedure take around 64 pictures a minute. Newer machines can take 128 to 256 pictures per minute.
When is it performed?
In patients who have a moderate to high suspicion of coronary artery disease, a CCTA may be considered. For example, if a patient who has a family history of heart disease undergoes a treadmill test that shows suspicious results (but not a strongly positive test), then a CCTA may be performed.
In brief, the likely indications of a coronary CTA are:
- Intermediate suspicion of coronary disease in patients with probable cardiac symptoms
- Ongoing symptoms of chest pain despite treatment for other causes
- Inconclusive treadmill test results in patients with a risk for heart disease
- Suspected birth defects in the coronary arteries
The choice of whether to perform a CCTA is usually made by the cardiologist who is treating the patient.
If a CCTA shows significant disease in the coronary arteries, then a full coronary angiography may be performed in the hospital to determine accurately the extent of disease.
Preparing for a CT coronary angiogram
Patients are advised the following:
1. Wear loose fitting, comfortable clothes
2. Ideally have an empty stomach (not to eat anything immediately before the test)
3. Avoid coffee (and other drinks with caffeine) the day of the test. This can increase the heart rate and make it difficult to perform the test.
4. Take off jewellery and keep it in a safe place (with a family member or friend)
A CCTA will not be performed in women who are pregnant due to risk of radiation exposure. It may not be appropriate in patients who have a history of kidney disease. It is never performed in patients who have a history of allergy to contrast material.
How is the procedure performed?
Patients may be asked to wear a gown prior to the procedure. Small ECG electrodes are attached to the chest wall at 3 distinct places. This helps monitor the electrical activity of the heart during the test.
A small cannula (intravenous line) will be inserted into the hand of the patient. This line will be used to inject contrast material. This contrast helps brighten up the arteries and can aid clear visualisation of their condition.
In patients who have a high heart rate, a dose of a beta blocker agent may be injected into the veins. This can help reduce the heart rate to a desired level so that clear images can be obtained during the study.
Sometimes, a small amount of nitroglycerin may be sprayed under the tongue (or may be given in form of a tablet) to help open up the arteries a little.
Patients will be asked to raise their arms above the level of their shoulders when images are being taken. It may be required to hold the breath for a few seconds so that any chest movements during respiration do not distort the image quality and clarity.
The CT scan machine will take around 1 minute to take a picture of the arteries. Once concluded, the patient is sat up and the cannula is removed from the hand.
The entire procedure can take around 15 to 20 minutes from preparation to image acquisition. If beta blocker drugs are given, it may take a little longer.
A CCTA is a painless procedure. The only part of the test that may hurt is the insertion of a cannula, which takes no more than a few seconds to do.
When contrast material is being injected, it is not unusual to feel a warm sensation ascend up the arm and around the body.
The CT scan is a large machine, and involves patients to lie down and be passed through the machine. The noise and the slight fear associated with the test can sometimes cause patients distress. However, there is no need to panic. There is always staff present to help if needed. Sometimes, certain centers may allow family members to be in the room with the patient.