Cardiac CT Scan - NHLBI, NIH
Also known as computed tomography; computed axial tomography scan (CAT scan).
A cardiac CT scan is a painless imaging test that uses x rays to take many detailed pictures of your heart and its blood vessels. Computers can combine these pictures to create a three-dimensional (3D) model of the whole heart. This imaging test can help doctors detect or evaluate coronary heart disease, calcium buildup in the coronary arteries, problems with the aorta, problems with heart function and valves, and pericardial disease. This test also may be used to monitor the results of coronary artery bypass grafting or to follow up on abnormal findings from earlier chest x rays. Different CT scanners are used for different purposes. A multidetector CT is a very fast type of CT scanner that can produce high-quality pictures of the beating heart and can detect calcium or blockages in the coronary arteries. An electron beam CT scanner also can show calcium in coronary arteries.
Your cardiac CT scan may be performed in a medical imaging facility or hospital. The scan usually takes about 15 minutes to complete, but can take more than an hour including preparation time and, if needed, the time to take medicines such as beta blockers to slow your heart rate. Before the test, a contrast dye, often iodine, may be injected into a vein in your arm. This contrast dye highlights your blood vessels and creates clearer pictures. You may feel some discomfort from the needle or, after the contrast dye is injected, you may feel warm briefly or have a temporary metallic taste in your mouth. The CT scanner is a large, tunnel-like machine that has a table. You will lie still on the table, and the table will slide into the scanner. Talk to your doctor if you are uncomfortable in tight or closed spaces to see if you need medicine to relax you during the test. During the scan, the technician will monitor your heart rate with an electrocardiogram (EKG). You will hear soft buzzing, clicking, or whirring sounds when you are inside the scanner and the scanner is taking pictures. You will be able to hear from and talk to the technician performing the test while you are inside the scanner. The technician may ask you to hold your breath for a few seconds during the test.
Cardiac CT scans have some risks. In rare instances, some people may have an allergic reaction to the contrast dye. There is a slight risk of cancer, particularly in people younger than 40 years old, because the test uses radiation. Although the amount of radiation from one test is similar to the amount of radiation you are naturally exposed to over one to five years, patients should not receive more CT scans than the number that clinical guidelines recommend. Another risk is that CT scans may detect an incidental finding, which is something that doesn’t cause symptoms now but may require more tests after being found. Talk to your doctor and the technicians performing the test about whether you are or could be pregnant. If the test is not urgent, they may have you wait to do the test until after your pregnancy. If it is urgent, the technicians will take extra steps to protect your baby during this test. Let your doctor know if you are breastfeeding because contrast dye can pass into your breast milk. If you must have contrast dye injected, you may want to pump and save enough breast milk for one to two days after your test or you may bottle-feed your baby for that time. People with asthma, chronic obstructive pulmonary disorder (COPD), or heart failure may have breathing problems during cardiac CT scans if they are given beta blockers to slow their heart rates for this imaging test.
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