A cardiac computed tomography coronary angiograpm scan (also called a CTCA) is used to examine the arteries supplying the heart safely and non-invasively. It is very good at detecting and quantifying calcium and plaque build up in the arteries, helping estimate cardiovascular risk and guide treatment of chest pain.
Over time, in patients with risk factors, the arteries of the heart can become furred up with cholesterol plaques and become calcified. Sometimes patients can have symptoms of chest pain or breathlessness, but often there are no symptoms – a situation which means that the opportunity to change lifestyle and take medications to reduce plaque build up can be missed.
There are two parts to the scan. Your expert Consultant Cardiologist will explain to you whether you need just the first part or the first and second parts.
The first part, “calcium scoring”, is a scan focussed on identifying calcium in the arteries. This doesn’t need any contrast, so you don’t need a plastic tube (cannula) in your vein and don’t need any blood tests checking beforehand. This part helps your doctor estimate your cardiovascular risk in the future but doesn’t usually identify if your chest pain or breathlessness is due to narrowings in the arteries. When you arrive in the scanner, some stickers will be placed on your chest and connected to the scanner with flexible wires so that the scanner can time the images with your heartbeat. You will be asked to hold your breath whilst you pass through the scanner. If you need this part of the scan only, you will be in the scanner for only a few minutes.
The second part is the angiography part which uses X-ray contrast injected through a plastic tube in a vein in your arm (cannula). This is used to visualise the arteries of the heart in detail and identify where and how severe any narrowings are. When you arrive your will be asked some brief questions about your medical history, including whether you have any kidney problems, asthma and allergies. The staff may need to check your kidney function with a blood test.
You will have the first part of the scan (“calcium scoring”) and the doctor supervising the scan will review your heart rate when you hold your breath. Avoiding a fast heart rate is important to make sure the images are good quality (and not blurred by the heart moving) and keep the radiation dose low. If the heart rate is too high, the doctor will suggest giving you some short-medicine (beta-blocker) through the cannula in your arm to reduce your heart rate slightly. If you need beta-blocker, they will monitor your heart rate and give further small doses until your heart rate has fallen low enough to do the scan. You may also be given a spray of glyceryl trinitrate (GTN) under the tongue which causes the blood vessels around the heart to swell in size and be seen more easily. The spray is minty and may give you a headache but this is normal and it wears off after a few minutes.
When ready, contrast will be injected in through the vein in your arm. It will be timed so that you are asked to hold your breath when the contrast arrives in the arteries around the heart.
If you need the angiography part of the scan you are likely to be in the scanner no more than 10-15 minutes in total. Before you get off the scanner, the team looking after you will check that they are happy with the quality of the images. Your Cardiologist will discuss the report with you.
If you have had medications to slow the heart, you will be observed for around 30 minutes after the scan before you are allowed to leave.
Calcium scoring is a useful test because it helps predict your risk of heart attack in the future. If you have no calcium in your arteries (sometimes known as a “zero score”) then the chance of you having a heart attack in the next 10 years is very low (probably less than 1%) and is therefore very reassuring. If you have a very high score, it may identify that you should begin lifestyle measures (stopping smoking, improving diet, losing weight, taking regular exercise) to reduce your risk. It may also suggest you take a statin, even if you have no symptoms, though this is a personalised decision and you should discuss it with your Cardiologist.
The coronary angiography part is now regarded by many as the first-line test for the investigation of chest pain. It is also used where there is concern of “silent” coronary disease such as an abnormal electrocardiogram (ECG), or other symptoms which might be due to coronary disease.
This is a safe test and the risks are very low. The test uses radiation but the dose with modern scanners is very low and the risks of missing coronary disease by not doing the test are higher in almost any situation. There is a very small (much less than 1 in 100) chance of a reaction to the contrast or medications given, but this is usually mild and easily treated at the time.
CT coronary angiography is a key test for patients with possible heart disease. Our expert Consultant Cardiologists are available for consultation on any day of the week and weekends as well.
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