A coronary calcium scan is a test that looks for specks of calcium in the walls of the coronary (heart) arteries. These specks of calcium are called calcifications (KAL-sih-fih-KA-shuns).
Calcifications in the coronary arteries are an early sign of coronary heart disease (CHD). CHD is a disease in which a waxy substance called plaque (plak) builds up in the coronary arteries.
Over time, plaque can harden or rupture (break open). Hardened plaque narrows the coronary arteries and reduces the flow of oxygen-rich blood to the heart. This can cause chest pain or discomfort called angina (an-JI-nuh or AN-juh-nuh).
If the plaque ruptures, a blood clot can form on its surface. A large blood clot can mostly or completely block blood flow through a coronary artery. This is the most common cause of a heart attack. Over time, ruptured plaque also hardens and narrows the coronary arteries.
CHD also can lead to heart failure and arrhythmias (ah-RITH-me-ahs). Heart failure is a condition in which your heart can't pump enough blood to meet your body's needs. Arrhythmias are problems with the rate or rhythm of your heartbeat.
Two machines can show calcium in the coronary arteries—electron beam computed tomography (EBCT) and multidetector computed tomography (MDCT).
Both use x rays to create detailed pictures of your heart. Your doctor will study the pictures to see whether you're at risk for future heart problems.
A coronary calcium scan is a fairly simple test. You'll lie quietly in the scanner machine for about 10 minutes while it takes pictures of your heart. The pictures will show whether you have calcifications in your coronary arteries.
Because calcifications are an early sign of CHD, a coronary calcium scan can show whether you're at risk for a heart attack or other heart problems before other signs and symptoms occur.
A coronary calcium scan is most useful for people who are at moderate risk for heart attacks. You or your doctor can calculate your 10-year risk using the Risk Assessment Tool from the National Cholesterol Education Program.
People who are at moderate risk have a 10–20 percent chance of having a heart attack within the next 10 years. The coronary calcium scan may help doctors decide who within this group needs treatment.
Some people refer to coronary calcium scans by the name of the machine used to take pictures of the heart:
You don't need to take any special steps before having a coronary calcium scan. However, your doctor may ask you to avoid caffeine and smoking for 4 hours before the test.
For the scan, you'll remove your clothes above the waist and wear a hospital gown. You also will remove any jewelry from around your neck or chest.
A coronary calcium scan is done in a hospital or outpatient office. The x-ray machine that's used for the scan is called a computed tomography (CT) scanner.
The technician who runs the scanner will clean areas of your chest and apply sticky patches with sensors called electrodes. The patches are connected to an EKG (electrocardiogram) machine.
The EKG will record your heart's electrical activity during the scan. This makes it possible to take pictures of your heart when it's relaxed between beats.
The CT scanner is a large machine that has a hollow, circular tube in the center. You'll lie on your back on a sliding table. The table can move up and down, and it goes inside the tunnel-like machine.
The table will slowly slide into the opening in the machine. Inside the scanner, an x-ray tube will move around your body to take pictures of your heart. The technician will control the CT scanner from the next room. He or she will be able to see you through a glass window and talk to you through a speaker.
The technician will ask you to lie still and hold your breath for short periods while each picture is taken. You may be given medicine to slow your heart rate. This helps the machine take clearer pictures of your heart. The medicine will be given by mouth or injected into a vein.
The coronary calcium scan will take about 10–15 minutes, although the actual scanning will take only a few seconds. During the test, the machine will make clicking and whirring sounds as it takes pictures. The scan causes no discomfort, but the exam room might be chilly to keep the machine working properly.
If you get nervous in enclosed or tight spaces, you might receive medicine to help you stay calm. Your head will remain outside the opening in the machine during the test.
You'll be able to return to your normal activities after the coronary calcium scan is done. Your doctor will discuss the results of the test with you.
After a coronary calcium scan, you'll get a calcium score called an Agatston score. The score is based on the amount of calcium found in your coronary (heart) arteries. You may get an Agatston score for each major artery and a total score.
The test is negative if no calcifications are found in your arteries. This means your chance of having a heart attack in the next 2–5 years is low.
The test is positive if calcifications are found in your arteries. Calcifications are a sign of atherosclerosis (ATH-er-o-skler-O-sis) and coronary heart disease (CHD). (Atherosclerosis is a condition in which plaque builds up in the arteries.) The higher your Agatston score is, the more severe the atherosclerosis.
The National Heart, Lung, and Blood Institute has a calculator you can use to see how your Agatston score compares with scores of people your age and of the same ethnic background.
An Agatston score of 0 is normal. In general, the higher your score, the more likely you are to have CHD. If your score is high, your doctor may recommend more tests.
Coronary calcium scans have very few risks. The test isn't invasive, which means that no surgery is done and no instruments are inserted into your body.
Unlike some CT scans, coronary calcium scans don't require an injection of contrast dye to make your heart or arteries visible on x-ray images.
Coronary calcium scans involve radiation, although the amount used is considered small. Electron beam computed tomography (EBCT) uses less radiation than multidetector computed tomography (MDCT).
In either case, the amount of radiation is about equal to the amount of radiation you're naturally exposed to in a single year.
The National Heart, Lung, and Blood Institute (NHLBI) is strongly committed to supporting research aimed at preventing and treating heart, lung, and blood diseases and conditions and sleep disorders.
NHLBI-supported research has led to many advances in medical knowledge and care. For example, an NHLBI study was the first to show that calcifications in the coronary arteries increase the risk of heart problems in multiple ethnic groups.
Much of the NHLBI's research depends on the willingness of volunteers to take part in clinical trials. Clinical trials test new ways to prevent, diagnose, or treat various diseases and conditions.
For example, new treatments for a disease or condition (such as medicines, medical devices, surgeries, or procedures) are tested in volunteers who have the illness. Testing shows whether a treatment is safe and effective in humans before it is made available for widespread use.
By taking part in a clinical trial, you may gain access to new treatments before they're widely available. You also will have the support of a team of health care providers, who will likely monitor your health closely. Even if you don't directly benefit from the results of a clinical trial, the information gathered can help others and add to scientific knowledge.
If you volunteer for a clinical trial, the research will be explained to you in detail. You'll learn about treatments and tests you may receive, and the benefits and risks they may pose. You'll also be given a chance to ask questions about the research. This process is called informed consent.
If you agree to take part in the trial, you'll be asked to sign an informed consent form. This form is not a contract. You have the right to withdraw from a study at any time, for any reason. Also, you have the right to learn about new risks or findings that emerge during the trial.
For more information about clinical trials related to coronary calcium scans, talk with your doctor. You also can visit the following Web sites to learn more about clinical research and to search for clinical trials:
The NHLBI updates Health Topics articles on a biennial cycle based on a thorough review of research findings and new literature. The articles also are updated as needed if important new research is published. The date on each Health Topics article reflects when the content was originally posted or last revised.