Coronary artery disease results in damage to the arteries primarily due to plaque and inflammation. Plaque deposits in and on the walls of coronary arteries can restrict the flow of oxygen-rich blood to the muscles of the heart. Plaque also may burst, triggering a blood clot that can cause a heart attack.
Plaque is composed of fats, cholesterol, calcium and other substances in the blood. Plaque deposits develop gradually over time, long before there are any signs or symptoms of disease. The imaging test provides an early look at calcium levels. If there is calcium, then there is already some stiffening and narrowing of the artery (atherosclerosis).
A heart scan uses a specialized X-ray technology called multidetector row or multislice computerized tomography (CT), which creates multiple images of the calcium deposits. The amount of detected calcium provides a measure of how much plaque has accumulated, and the data from the scan are used to calculate a score. When combined with other health information, your doctor may use the test score to refine a treatment plan for reducing your risk.
When is a heart scan used?
A heart scan is generally considered useful for people who have a known moderate risk of heart disease or when the risk is uncertain. There are different tools for an initial risk assessment, but all of them use factors, such as your age, sex, blood pressure, cholesterol levels and tobacco use. A moderate risk is generally defined as a 5 to 7.5 percent chance of a heart attack in the next 10 years or when the risk is calculated to be low, but there is a history of heart attacks at an early age in the family.
The American College of Cardiology and the American Heart Association guidelines published in 2013 on cardiovascular risk assessment suggested that it would be reasonable to perform coronary calcium heart scans for people with a calculated risk of 5 to 7.5 percent or when "a risk-based treatment decision is uncertain."
Some studies have demonstrated that a heart scan may be a motivational factor for people at moderate risk to make lifestyle changes and follow treatment plans.
When is a heart scan not used?
A heart scan does result in radiation exposure. While this exposure is generally considered safe, it is not recommended when there is no likely benefit to getting the scan. In other words, when the scan is not likely to provide any information that is useful in defining your risk or directing a treatment plan, the risk of radiation exposure outweighs any potential benefit.
According to the American College of Cardiology and the American Heart Association guidelines, a heart scan is generally not recommended for the following people:
- Men under age 40 and women under age 50, because detectable calcium at younger ages is not likely
- People who have a low risk, because detectable calcium is highly unlikely, in the absence of family history of heart attacks at early age
- People who already have a known high risk, because the heart scan will likely not provide any additional information to guide treatment decisions
- People who already have symptoms or a diagnosis of heart disease, because the procedure would not help doctors better understand the disease progression or risk
- People who already had an abnormal coronary calcium heart scan