A cardiac CT scan combines computer-generated images 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 and valve function, and pericardial disease.
This test may also be used to monitor the results of coronary artery bypass grafting or to follow up on abnormal findings from previous 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 images of the heartbeat and can detect calcium or blockages in the coronary arteries. An electron beam CT scanner can also show calcium in the coronary arteries.
Cardiac computed tomography. Source: Scheffel H, Alkadhi H, Plass A, Vachenauer R, Desbiolles L, Gaemperli O, Schepis T, Frauenfelder T, Schertler T, Husmann L, Grunenfelder J, Genoni M, Kaufmann PA, Marincek B, Leschka S.
A cardiac CT procedure may be performed in a medical imaging facility or hospital. The scan usually takes about 15 minutes, but can take over an hour including preparation time and, if necessary, the time to take medications such as beta-blockers to slow your heart rate.
Prior to the test, a contrast dye, usually iodine, may be injected into a vein in your arm. This contrast dye highlights your veins and creates clearer images. You may feel some discomfort from the needle or, after the contrast dye is injected, you may feel brief warmth or experience a temporary metallic taste in your mouth.
The CT scanner is a large, tunnel-like machine that has a table. During the procedure, you will lie still on the table, and the table will slide toward the scanner. Tell your doctor if you feel uncomfortable in a tight or closed space to see if you need medication 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 while the scanner is taking pictures. You will be able to hear from and talk to the technician who performs the test while you are inside the scanner. The technician may ask you to hold your breath for a few seconds during the test
Coronary Calcium Scoring. Source: NHLBI / NIH
A cardiac CT scan carries several risks. In rare cases, some people may have an allergic reaction to the contrast dye. There is a small risk of cancer, particularly in people younger than 40 years old — since the test uses radiation. Although the amount of radiation from one test is similar to the amount of radiation exposure you naturally get for over one to five years, patients should not have more CT scan procedures than recommended by clinical guidelines. Another risk is that a CT scan may detect incidental findings — which are things that do not cause symptoms now but may require more tests once they are detected.
Talk to your doctor and the technician who performs the tests about whether you are pregnant or may be pregnant. If the test is not urgent, you may have to wait to do the tests until after your pregnancy. If it is urgent, the technician will take extra steps to protect your baby during this test. Let your doctor know if you are breastfeeding because the contrast dye can pass into your breast milk. If you have to use an injected contrast dye, you may need to pump and store enough milk for one to two days after the test or you may bottle-feed your baby for that time.
People who have asthma, chronic obstructive pulmonary disease (COPD), or heart failure may experience breathing problems during a cardiac CT scan procedure if they are given beta-blockers to slow their heart rate for this imaging test.