Definition
A CT Coronary Angiogram is an outpatient non-invasive X-ray imaging technique performed with intravenous contrast (dye) to produce high-resolution three-dimensional images of the moving heart, great vessels and heart arteries using state-of-the-heart computer software.
Using state-of-the-art computerized tomography (CT) methods, calcium and fatty deposits in atherosclerotic plaques in the arteries of the heart can be detected accurately and clearly with much lower radiation doses than before.
What are the benefits of this test?
This test is used to:
- 1Diagnose the presence of coronary artery disease
- Early stage coronary artery disease is often not detected by electrocardiograms or non-invasive treadmill tests as exemplified by the diagram above.
- This test picks up heart artery blockages even in the very early stages of coronary artery disease so that treatments to reduce the progression to severe blockages and heart attacks can be initiated early.
- This test also allows a definitive evaluation of patients with chest pain with non-typical symptoms or unclear/equivocal stress test results.
- 2Assess the severity of narrowing of the coronary arteries
The degree of narrowing of the coronary arteries caused by the fatty and calcified deposits can be accurately calculated and guide your physician in planning the next step of treatment needed (eg more aggressive lifestyle modifications, taking cardiac medications or proceeding with stenting or bypass surgery)
- 3Assess patency of stent or coronary bypass grafts
Pictures of a patent coronary stent using CT Coronary Angiogram
Pictures of a patent coronary artery bypass graft on CT coronary angiogram
- The risk of blockages developing within coronary stents and bypass grafts increases with time and especially if risk factors such as diabetes, hypertension and high cholesterol are not well controlled.
- This test may be used by your physician to assess the health of your stent or bypass grafts as clinically indicated. This reduces the need for an invasive assessment of the coronary arteries via a cardiac catheterization.
- 4Guide stenting of complex coronary artery disease
- To increase the success of treating complex and difficult to treat heart artery blockages, CT coronary angiogram has been proven to be very useful in increasing the success rates of these procedures.
- 5Diagnose coronary artery anomalies that can lead to sudden cardiac death
Who will benefit from this test?
- Patients with atypical chest pain and intermediate risk for coronary artery disease with the following risk factors.
- Family or personal history of coronary artery disease
- Male over 45 years of age
- Females over 55 years of age
- Past or present smoker
- History of high cholesterol, diabetes or high blood pressure
- Elevated body mass index (BMI)
- Inactive lifestyle
- Patients with new or worsening symptoms (eg Chest pain or shortness of breath) with a previous normal stress test result
- Patients with inconclusive stress test results (eg borderline positive treadmill test)
- Patients with new onset heart failure with reduce ejection fraction with low or medium risk for coronary artery disease
- Patients suspected of having anomalous coronary arteries
- Post stenting or bypass patients with new/worsening symptoms
- Patients with unexplained and recurrent syncope (fainting) or history of sudden cardiac arrest
Are there any side effects of this test?
Adverse side effects to the contrast agent (dye)
- Itch and rashes which are usually self-limiting and resolve without further treatment. Anti-histamines can be administered if needed for symptomatic relief.
- Anaphylactic reactions is a more serious allergic reaction which can result in breathing difficulties. This is very rare (less than 1 in 2000). All centers have radiologists ready to handle this emergency if it occurs.
- Contrast induced nephropathy (Impairment of kidney function due to the dye injection) is very rare if adequate precautions are taken to ensure you are well-hydrated before and after the procedure.
X-ray exposure
- CT scanners use X-ray to image the heart and current state-of-the-art scanners permits the scan to be carried out in the majority of patients with much lower radiation doses than before.
How to prepare for the test
Before the day of the test
- Take the morning off so that you can complete this test in a more relaxed state of mind. Stress increases your heart rate and it can make this test less accurate.
- Keep yourself well-hydrated. This will reduce the risk of kidney impairment due to the injection of the dye.
- Stop diabetic medications containing Metformin (eg Glucophage).
On the day of the test
- You may drink water and consume all your medications (except Metformin) but do not eat for 4 hours prior to your scheduled appointment.
- Avoid any caffeinated drinks (eg coffee, tea, mountain dew, energy drinks)
- Inform the radiographer and your doctor if you are:
- Pregnant
- Allergic to iodine and/or shellfish or any medications
- Undergoing radiation therapy
- Have a history of kidney problems (you may be required to undergo a blood test to evaluate your kidney function prior to injection of the dye)
How is the test performed?
This exam will take place in a radiology center chosen by your physician.
- 1Before the test
- You will change into a hospital gown.
- The nurse will record your height, weight and blood pressure and insert an intravenous (IV) cannula into a vein in your arm.
- You will lie on a special scanning table.
- Three electrodes (small flat sticky patches) will be placed on your chest wall and attached to an ECG monitor that charts your heart’s electrical activity during the test.
- 2During the test
- You will feel the table move inside a donut-shaped scanner and when your heart rate is suitably low, you will receive an injection of dye. It is common for you to feel a warm sensation as the contrast circulates through your body.
- The high-speed CT scanner will capture multiple images, synchronised with your heart beat to detect the presence of calcification within the coronary arteries and capture all the images needed to answer the clinical question asked by your physician.
- Once the radiographer is sure that all the information is collected, the IV will be removed.
- The entire procedure may take 30-45mins, but the actual CT scan only takes a few seconds.
- 3After the test
- You may resume your normal daily activities after the exam.
- You CT coronary angiogram with be reviewed by our doctor and a summarized report will be provided and explained to you during your review.
How does the doctor use this test to treat me?
- 1Normal exam
- No further testing may be needed.
- 2Abnormal exam
- Further investigations such cardiac catheterization may be needed.
- Lifestyle changes and treatment with cardiac medications to optimize your condition will be given by your physician.
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