CT Calcium Score

Introduction

The coronary artery calcium score is a measurement of the amount of calcium in the walls of the arteries that supply your heart muscle, using a special computed tomography (CT) scan of your heart. As you age, plaque can build up inside your arteries. This is often called hardening of the arteries (the medical term is atherosclerosis). Over time, calcium deposits in the plaque, hence the amount of calcium present gives doctors a guide to how much plaque is present. Calcium scoring does not measure how narrow the arteries are, rather it is a way of looking at the overall amount of cardiac plaque present, which can help predict your risk of a future cardiac event.

Calcium is reported using a measure called Agatston units. Calcium scores vary with age. The older you are the more likely you are to have some degree of calcium in your arteries. The calcium score report may give an indication of how you compare to an average person of the same age and sex and ethnic race. This is calculated using the MESA calculator (mesa-nhlbi.org). Alternatively, it may be reported as your estimated arterial age. For example, if you are a 50-year-old male with a high calcium score you may be reported as having the arterial age of an 80-year-old. 

Your doctor will use the calcium score to decide whether you are at low, normal or high risk of a future heart attack and give you guidance on how to reduce your risk. This may be by changes to your diet, exercise, controlling blood pressure and diabetes, stopping smoking and reducing cholesterol.

It must be emphasised that this is a screening test. If you have symptoms, for example chest pain or breathlessness, then a CTCA (a more detailed test than a CT calcium score) would be advisable.

Benefits of Calcium Scoring

The benefit is having a better understanding of the relative risk for you of having a heart attack or stroke in the future and using that information to decide which strategies you should adopt to reduce your risk if the risk is found to be high.

The calcium score is of no benefit to someone who has already had a heart attack, coronary bypass surgery or a coronary artery stent. These events indicate that you are already have coronary artery plaque. The score does not change enough to be meaningful after treatment for atherosclerosis, which is hardening and narrowing of the arteries, so it does not tell you whether your treatment is working or not.

Your doctor may decide that a second calcium score scan after a few years may be helpful to compare results to the previous scan. Coronary calcium scores are most informative in a woman between 35 and 70 years and in a man between 40 and 60 years in terms of providing information about cardiovascular risk, or the risk of a heart attack or stroke. People over 80 years almost all have high calcium scores and therefore such a scan would not provide any useful information.

What happens during coronary artery calcium scoring?

On arrival at the practice, you will be asked to provide your personal details and then be taken to the scanner. The scanner has a round opening in the X-ray machine through which a table moves. You will lie on this table and the table moves through the opening during the scan. The scan uses a recording of the electric pulses from your heart every time it beats using an electrocardiogram (or ECG) to control the processing of the CT scan images. You will be asked to hold your breath, the table will move and the pictures of the heart will be taken. The radiographer will check that the scan is diagnostic, and then you can go. The scan results will be sent to the doctor who referred you, so you can discuss the score and how it can be used to help you.

Results

The time that it takes your doctor to receive a written report on the test or procedure you have had will vary, however most reports are available within 24 hours of the test being performed. Please feel free to ask when your doctor is likely to have the written report.

It is important that you discuss the results with the doctor who referred you, either in person or on the telephone, so that they can explain what the results mean for you.