Wednesday, June 29, 2011

Coronary CT Scans: Dangerous and Best Avoided

I am asked by many patients if they should get a coronary CT scan to evaluate the status of their coronary arteries. Coronary CT scans are a noninvasive way to visualize calcification in the coronary arteries. The only other way to visualize atherosclerotic changes in the coronary arteries is through an angiogram where a catheter from the groin is thread to the coronary arteries.

It must be better to do a coronary CT scan--versus an angiogram-- since it is non-invasive—right? The answer to this question is easy; coronary CT scans should be avoided.

As a population, we undergo too many CT scans. CT scans expose the body to a huge amount of radiation. A coronary CT scan can supply 100x the radiation of a chest X-ray. There are estimates that over two percent of all cancers in the U.S. are the result of too many X-ray procedures with CT scans being the leading radiologic cause of harmful medical radiation.
You would expect an effective medical screening test would lead to early diagnosis in order to improve the outcome of the disease—correct? In the case of heart disease, coronary CT scans should be able to safely diagnose atherosclerosis before a problem develops. Furthermore, the treatment plan should result in a lowered cardiac event rate (i.e., less heart attacks and death).

Researchers studied a group of 1,000 patients who underwent a coronary CT scan. In the 1,000 patients who had the coronary CT scan, 215 had a positive test indicating that they had advanced atherosclerosis. Compared to the group who did not test positive, the positive CT-scanned group were prescribed statins at a 700% higher rate. Furthermore, as compared to the negatively screened group, the positive CT-scanned patients also had four times as many secondary cardiac tests (including angiograms) as well as bypass surgeries at a 10x higher rate.

Since the positive CT-scanned group received the various medical interventions, you would hope that they would have a better long-term outcome. However, the opposite occurred. The researchers found that there was no difference (at 18 months) in cardiovascular events (e.g., heart attacks, cardiac deaths, and angina requiring hospitalization) between the two groups.

What can we conclude here? Coronary CT scans did not result in less cardiac adverse events but did result in more medication usage, surgery and testing. And, don’t forget, the positive coronary CT scans resulted in a lot of money being spent on therapies that did not change the outcome. Finally, all the patients who underwent the coronary CT scans were exposed to a large amount of damaging radiation.

There is no place for coronary CT scans. They are used as a diagnostic modality only. Coronary CT scans expose patients to excess amounts of ionizing radiation and they have not been shown to improve the cardiac event rate. They are not worth the risk.

Arch. of Int. Med. Online. May 23, 2011.


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