Because an x-ray machine is used, cardiac CT involves radiation. Although the amount of radiation used is considered small, it's similar to the amount of radiation you're naturally exposed to over a 3-year period.
There's a small chance that cardiac CT will cause cancer because of the radiation involved. The risk is higher for people younger than 40 years old, especially children. However, new cardiac CT methods are available that reduce the amount of radiation used for this test.
Cardiac CT scans are painless. Some people feel side effects from the contrast dye that's sometimes used during the cardiac CT scan. An itchy feeling or a rash may appear after the contrast dye is injected. Neither side effect normally lasts for long, so medicine often isn't needed.
If you do want medicine to relieve the symptoms, your doctor may prescribe an antihistamine. This type of medicine is used to help stop allergic reactions.
Although rare, it's possible to have a serious allergic reaction to the contrast dye that causes breathing problems. Medicines are used to treat serious reactions.
People who have asthma, COPD (chronic obstructive pulmonary disease), or heart failure may have breathing problems during cardiac CT if they're given beta blockers to slow down their heart rates.