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What Are the Risks of Cardiac CT?

Cardiac CT involves radiation, although the amount used is considered small. Depending on the type of CT scan you have, the amount of radiation is similar to the amount you’re naturally exposed to over 1–5 years.

There is a small chance that cardiac CT will cause cancer because of the radiation. The risk is higher for people younger than 40 years old. New cardiac CT methods are available that reduce the amount of radiation used during the test.

Cardiac CT scans are painless. Some people have side effects from the contrast dye that might be used during the scan. An itchy feeling or a rash may appear after the contrast dye is injected. Normally, neither side effect 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 is possible to have a serious allergic reaction to the contrast dye. This reaction may cause breathing problems. Doctors use medicine to treat serious allergic 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 their heart rates.

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Cardiac CT Clinical Trials

Clinical trials are research studies that explore whether a medical strategy, treatment, or device is safe and effective for humans. To find clinical trials that are currently underway for Cardiac CT, visit

February 29, 2012 Last Updated Icon

The NHLBI updates Health Topics articles on a biennial cycle based on a thorough review of research findings and new literature. The articles also are updated as needed if important new research is published. The date on each Health Topics article reflects when the content was originally posted or last revised.