Coronary Artery Disease and CT Scanning

Coronary Heart Disease is a leading cause of death. Making an early diagnosis and taking preventive measures are possible with the help of various tests, which more recently include CT scanning. This article will explain in simple terms what Coronary Heart Disease is, its symptoms, and how CT imaging can help in its diagnosis and treatment.

What is Coronary Artery Disease?

This is the narrowing and blockage of the arteries leading to the heart. These arteries supply your heart with blood, which in turn supplies the rest of your body with essential oxygen and nutrients. In simple terms, if your heart doesn't get its needed supply of oxygen and nutrients, you may experience chest pain. When one or more of your arteries becomes blocked, you may experience a heart attack.

Can I get Coronary Artery Disease?

There are two types of risk factors for this disease: non-modifiable risks and modifiable risks. A non-modifiable risk factor is one you can't change such as family history, old age and sex - males are more prone than females. A modifiable risk factor is one associated with your lifestyle which can be altered, such as cigarette smoking, high blood cholesterol, high blood pressure, being overweight, uncontrolled stress, a diet high in fat and alcohol, and uncontrolled diabetes.

What are the symptoms of Coronary Artery Disease?

Consult your doctor if you have any of the following symptoms:

• Chest pain, especially on exertion
• Shortness of breath
• Palpitations
• Nausea
• Extreme weakness
• Dizziness

The Role of CT Scanning in Diagnosing Coronary Artery Disease

Traditionally, the most common test for Coronary Artery Disease is the coronary angiogram - an invasive test where a catheter is inserted into a blood vessel in your thigh and manoeuvred up to your coronary arteries. A contrast medium, like a dye, is injected so that the image can be seen on X-ray. CT scanning gives your doctor an alternative test which is less invasive and is accurate in ruling out significant narrowing and blockage of the coronary arteries. This relatively new technology is being used increasingly today to help detect plaque build-up and significant narrowing of the coronary arteries.

What exactly is CT scanning?

Computed Tomography (CT) scanning or CAT scanning is an x-ray based imaging technique that takes multiple cross-sectional images that are fused on a computer to produce pictures of your heart and blood vessels. These state-of-the-art scanners can acquire high resolution images of the heart within several seconds.

What can CT scanning do?

This can be used to assess your risk of Coronary Artery Disease in two ways: Coronary Calcium Score Scans and Coronary CT Angiography (CTA).

• Coronary Calcium Score Scan
  This is a test that only takes a few minutes and does not require an injection of the iodine contrast dye, or any other special preparation. CT scanning is done to detect the amount of calcium build-up in your arteries. This is a powerful predictor of future risk of heart attack and allows your doctor to guide your treatment including advice on lifestyle changes that need to be made. While absence of a positive score may put you at low risk of future heart problems, in some instances you may have what is known as soft plaque, which is not detected with calcium scoring but can be depicted on CTA.
  
  
• Coronary CT Angiography (CTA)
  This is a CT scan that requires an intra-venous injection of iodine based contrast dye. A type of medication called a "beta-blocker" may be required to help slow down the heart rate before the scan. During the scan, another tablet called a "nitrate" is often placed under the tongue, where it is absorbed and helps make the coronary arteries bigger and easier to see. While the scan itself may only take a few seconds, the preparation and planning before the scan may take half an hour or more.

Neither scan requires an overnight stay in the hospital or clinic. It is important to discuss the results with your doctor so that any lifestyle changes or other treatments can be planned.

Are there any risks to the procedure?

As with any CT scan, you will be exposed to X-rays. However, we will try to minimise your exposure by using the lowest X-ray dose possible but which is sufficient to maintain a good quality scan. It is important that any risk from an x-ray exposure is justified by the potential benefits from the scan.

Some people experience a warm sensation during the contrast injection, slight nausea or a metallic taste in the mouth. However, true allergic reactions to the injection are rare, occurring in about 1 in 10,000 individuals.

As with any radiology examinations, you should advise your doctor if you are pregnant or suspect you could be.

What are the benefits?

• CT scanning is a relatively non-invasive procedure that can be used to rule out coronary heart disease.
• No significant down time. You are ready to leave almost as soon as the scan is finished. No overnight stay in hospital is required.
• A clear picture of not just the heart but surrounding areas.
• It costs less than a conventional catheter angiogram.

How do I prepare for the procedure?

• Do not eat or drink for 4 hours before the procedure.
• Inform your doctor if you have asthma, kidney problems, known heart conditions, diabetes, and drug allergies or if you are pregnant or suspect you could be.