CT Coronary Angiography is an advanced imaging technique that uses the (Computed Tomography) scanner to obtain detailed images of the heart and coronary arteries.
The coronary arteries are the blood vessels that supply the heart muscles with oxygen-rich blood. A CT Coronary Angiography is mainly used to check for narrowed or blocked coronary arteries. It can tell if there are mild, moderate or severe build-up of cholesterol plaque.
Coronary artery disease develops when the arteries that supply blood to your heart become narrowed or blocked by a build-up of fatty cholesterol deposits called plaque. This process is known as atherosclerosis and develops over time.
Your doctor may suggest a CT Coronary Angiogram for the following reasons:
- You may have symptoms suggestive of coronary artery disease. This includes chest pain or angina, pain radiating to your jaw or arm, nausea, heartburn, shortness of breath, heaviness in the chest, and heavy sweating.
- You have prior investigations suggestive of coronary artery disease.
- To check for worsening of pre-existing coronary artery disease.
- To check on the outcome of previous coronary treatment (angioplasty or bypass surgery).
- You may have significant risk factors for coronary artery disease such as family history, smoking, high cholesterol or high blood pressure.
| CT Coronary Angiography | Coronary Angiography |
| Non-invasive | Minimally invasive |
| Done as an outpatient test | Requires hospital admission (either day surgery or inpatient) |
| Involves injection of contrast dye through an intravenous cannula (plastic needle or drip line) | Involves the insertion of tubes (catheters) to the heart via the wrist or groin artery, and contrast dye is injected into the coronary arteries directly |
| Diagnostic test | Coronary Angiography, Angioplasty (ballooning and stenting) can take place in the same setting
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While CT Coronary Angiography is highly accurate, you may still require Coronary Angiography to confirm the degree of narrowing or blockages in your coronary arteries, and whether the narrowing needs to be treated with Angioplasty (ballooning and stenting).
Comparison of lesions on CT Coronary Angiogram (left) and conventional Coronary Angiogram (right)
- Your doctor may prescribe a medication to take the night before the scan and on the morning of the scan. This medication lowers the heart rate, and enables better quality and more accurate images to be taken.
- If you have asthma or known allergy to contrast dye, your doctor will prescribe a medication to reduce the risk of an asthmatic attack or allergic reaction.
- You can take all your usual medications except metformin on the day of the scan. If you are using regular inhalers, please bring them along.
- Do not take Cialis, Viagra, Levitra or similar medications for 36 hours before the scan.
- You will change into a gown and have your blood pressure and heart rate monitored. ECG leads will be placed on your chest.
- You will be assessed by the staff, and you may be given additional medications as determined by them.
- An intravenous cannula (small plastic needle) will be inserted in the vein near your elbow.
- You will be given a GTN spray under the tongue just before the start of the scan.
- You will lie on a padded couch that will move through a round opening of the scanner.
- You may be asked to hold your breath for up to 15 seconds and to lie flat for 5-10 mins during the scan. Please follow the instructions of the staff.
- During the injection of contrast dye, you may notice a warm sensation and a metallic taste. This is normal and will disappear after a few minutes.
- Upon completing the scan, you will be monitored for about 10 minutes to ensure you are well before leaving.
Although the scan itself takes less than 15 minutes, the whole process including preparation may take up to 2 hours.
There are minimal risks associated with a scan.
- Radiation: The CT scanner uses the lowest radiation dose possible to obtain the best images of your heart and coronary arteries, and amounts to just a small fraction of the usual background radiation acquired in a year.
- Allergic reaction to contrast dye: Very rarely people experience mild allergic reactions such as a rash which usually resolves by itself. Life-threatening reaction (anaphylaxis) is extremely rare (1 in 250000). Patients with asthma may experience worsening of their asthma temporarily after contrast dye injection. Patients with kidney failure may experience worsening of their kidney function temporarily after contrast dye injection.
- Leakage of contrast dye: The contrast dye may rarely go into the surrounding tissue and cause swelling and bruising. This will usually resolve by itself.
Your doctor will review the findings of the CT Coronary Angiography and discuss the results of your test during your next follow-up appointment. You may be contacted earlier if urgent care is required for your condition. Further tests may be recommended if abnormalities are detected.
