Cardiac Computed Tomography (Multidetector CT, or MDCT)

What is Computerized Tomography (CT)?

CT is a noninvasive test that uses X-rays to make pictures of your heart. Modern CT scanners (multidetector CT or MDCT) work fast and are detailed. They can take images of the beating heart, and show calcium and blockages in your heart arteries.

Why do people have MDCT?

You may need to have MDCT when other tests, such as chest X-rays, electrocardiograms (ECG), echocardiograms (echo), or stress tests, don’t give your health care team enough information about your heart.

Through MDCT, your health care team may gather additional information on:

• Your heart’s structure and how well your heart pumps blood.
• Scarring of the heart muscle caused by a heart attack. 
• Fluid in the pericardial sac that covers the surface of the heart.
• The amount of plaque buildup and narrowing of your coronary arteries.
• Any abnormalities in the large blood vessels leaving the heart.
• Your risk for a heart attack.

Can it help show if you have heart disease?

When contrast dye (iodine) is given during the scan, MDCT show blockages in your heart arteries. This is useful to see if chest discomfort comes from lack of blood flow to the heart muscle due to blocked heart arteries (angina). If the heart arteries are normal, your health care team can confidently look into other causes of chest pain that aren’t related to the heart.

With contrast dye, MDCT can also check if coronary artery bypass grafts remain open and detect congenital heart defects (problems present at birth) and how your ventricles are working.

Without contrast dye, MDCT can measure the amount of calcium in your heart arteries (“calcium score”). Your calcium score gives doctors an idea of how much plaque is in your heart arteries that hasn’t yet caused problems. Your calcium score may help predict your risk of a heart attack, and determine how much more aggressive you and your health care professional should be to reduce your risk factors. This is particularly helpful if you're at “intermediate” risk.

Calcium scoring is not recommended for routine screening of people who don’t have symptoms of heart disease and have a low risk of heart attacks unless they have a strong family history of premature coronary heart disease. If you’ve already had a heart attack, coronary bypass surgery or a coronary stent (PDF), calcium scoring won’t provide additional information.

Can I have MDCT instead of a coronary angiogram?

MDCT is not a substitute for a coronary angiogram (PDF) or cardiac catheterization. Coronary angiography is the gold-standard method for showing blockages in the coronary arteries. It also gives specific information about how your heart is working.

What are the risks?

MDCT exposes you to a higher dose of X-rays. Further studies on safety and possible risks are warranted. Talk with your health care team about safety and risks for any test you’re undergoing.

Tell your health care team if you’re pregnant. If it’s not urgent, the test can be delayed until after your pregnancy.  Also, you should not take the test if you have kidney problems. The contrast dye can worsen kidney function.

Some people have allergic reactions to the contrast dye that’s sometimes used in the test. Before the test, tell your health care professional if you’re allergic to dyes, iodine or shellfish.

How do I prepare for MDCT?

If contrast dye will be used during the test, don’t eat for four to six hours before the test.

What happens during the test?

Technicians perform MDCT in hospitals or special outpatient clinics.

• Electrodes will be attached to your chest to monitor your ECG. The ECG also helps the computer connected to the CT scanner create clear pictures of your heart.
• When you're ready, the table slowly moves inside the machine. The scanner arches around you but doesn’t touch you.
• If a contrast dye is used, it's injected through an intravenous line (IV) placed in an arm vein.
• The technician will watch you closely through a window. You can talk to him or her through a two-way intercom.
• The technician will ask you to hold your breath for short periods.
• MDCT scanning takes about 5-10 minutes.

What happens after MDCT?

• Your health care professional will inform you on when to resume normal activities.
• After the health care team gets a written report of the test results, make an appointment to discuss the results and next steps.