A coronary CT angiogram is a test that can check your heart for various conditions, but it's primarily used to check for narrowed arteries in your heart (coronary artery disease) that could explain chest pain or could put you at risk of a heart attack.

Coronary CT angiograms are sometimes used instead of traditional coronary angiograms to check for coronary artery disease. A CT angiogram may be better than a traditional angiogram for people who have only a moderate risk of coronary artery disease.

Typically, when your doctor needs to check for blockages in your heart's arteries, he or she will perform a coronary angiogram. In a coronary angiogram, a catheter is inserted in an artery in your groin and threaded through your blood vessels to your heart. Dye that's visible on X-rays is then injected through the catheter, and X-ray images of your heart are taken.

Your doctor can see blockages and areas of narrowing in your heart's arteries on the images. Because the catheter is near your heart, if blockages are found, your doctor can perform a procedure called angioplasty to open your blockages after a traditional angiogram. However, many people who have coronary angiograms don't have any blockages.

In a CT angiogram, no catheter has to be placed in your groin, and the dye that's visible on the CT scan is injected through an intravenous (IV) line that's placed in your hand or arm. X-ray images are still taken of your heart. However, because no catheter is used, if you need treatment to improve blood flow to the heart, you'll need a separate procedure (a traditional coronary angiogram) to treat your condition.

A test that's similar to CT angiogram is a coronary calcium scan. This test uses a special type of computerized tomography to check for calcium in your coronary arteries, which can be a risk factor for coronary artery disease. No dye is injected during a coronary calcium scan.

Because CT angiograms use an X-ray machine to take pictures of your heart, you will be exposed to some radiation during the test. The amount of radiation varies depending on the type of machine used.

With the most common type of X-ray machines, the radiation you're exposed to during the test is about the same as the average American is naturally exposed to over one to five years. The risk that you could develop cancer from the radiation you receive during a CT angiogram is not known exactly, but is very small.

Because radiation can harm an unborn child, you shouldn't have a CT angiogram if you're pregnant.

It's also possible that you could have an allergic reaction to the dye used in the procedure. Talk to your doctor if you're concerned about having an allergic reaction.

Your doctor should give you instructions about how to prepare for your CT angiogram. Usually, you'll be asked not to eat anything for about four hours before your test.

You can drink water, but avoid caffeinated drinks before your test, because they can speed up your heart rate. This can make it difficult for your doctor to get clear pictures of your heart.

You can drive yourself to the appointment, and you'll be able to drive home or to work after your test.

During the procedure

CT angiograms are usually performed in the radiology department of a hospital or an outpatient imaging facility.

Just before you begin your scan, you'll need to remove clothing above your waist, as well as any jewelry. You'll change into a hospital gown.

Because your heart's constantly in motion while it beats, your doctor may give you a medication called a beta blocker, which will slow your heart rate. This will allow the doctor to see your heart more clearly. Some people have side effects from beta blockers, such as shortness of breath or wheezing in some people with asthma or chronic obstructive pulmonary disease (COPD). Let your health care provider know if you've had side effects from beta blockers in the past.

Some newer CT machines can be used without slowing the heart rate down. However, when beta blockers can be used, a slowed heart rate generally produces the clearest CT images.

A technician will insert an intravenous (IV) line in your hand or arm to inject the dye that will make your heart's arteries visible on the images taken by the CT scanner. You'll receive some numbing medication before the IV is inserted. Although the actual scanning portion of the test takes as few as 5 seconds, it may take up to an hour for the whole process because beta blockers need time to slow your heart rate sufficiently.

The technician will place some electrodes on your chest to record your heart rate throughout the exam. When you're ready to be scanned, you'll lie on a long table that slides through a short, doughnut-like machine.

During the test, an X-ray tube will move rapidly around your chest to take images of your heart from many different angles. You won't see the tube moving.

A technician will operate the machine from a room that's separated from your exam room by a glass window. There will be an intercom system the technician can use to talk to you.

It's important to stay as still as possible and hold your breath during the scanning portion of the exam. Any movement can blur the X-ray images.

After the procedure

After your CT angiogram is completed, you can return to your normal daily activities. You should be able to drive yourself home or to work.

The images from your CT angiogram should be ready soon after your test. Usually, the doctor who asked you to have a CT angiogram should discuss the results of the test with you.

Based on the results of your test, your doctor will discuss with you whether you have a heart condition that needs treatment, whether you're at risk of developing heart disease, and steps you can take to keep your heart healthy. Treatments may vary, depending on what condition your doctor suspects you have.

Regardless of the results of your test, it's a good idea to make lifestyle changes to help protect your heart. These include:

• Exercise regularly. Exercise helps you reach and maintain a healthy weight and control diabetes, elevated cholesterol and high blood pressure — all risk factors for heart disease. With your doctor's OK, aim for 30 to 60 minutes of physical activity most days of the week. Even if you can't make time for one 30- to 60-minute exercise session, you can still benefit from breaking up your activity into several 10-minute sessions.
• Eat healthy foods. A heart-healthy diet based on fruits, vegetables and whole grains — and low in saturated fat, cholesterol and sodium — can help you control your weight, blood pressure and cholesterol. Eating one or two servings of fish a week also is beneficial.
• Stop smoking. Smoking is a major risk factor for heart disease, especially atherosclerosis. Nicotine constricts blood vessels and forces your heart to work harder, and carbon monoxide reduces oxygen in your blood and damages the lining of your blood vessels. If you smoke, quitting is the best way to reduce your risk of heart disease and its complications.
• Maintain a healthy weight. Excess weight can contribute to high blood pressure, abnormal cholesterol levels and type 2 diabetes. Losing weight lessens these risks. Even a small weight loss of just 5 to 10 percent of your body weight helps reduce your risk.
• Manage health conditions. If you have high blood pressure, elevated cholesterol or diabetes, be sure to take your medications as directed. Losing weight, eating healthy and exercising regularly can help control these heart disease risk factors too. Ask your doctor how often you need follow-up visits.
• Manage stress effectively. Stress can cause your blood vessels to constrict, upping the odds of a heart attack. Ask your doctor about stress management programs in your area. Exercise can help reduce stress too.