Study: Heart CT Scans May Pose Risk

A new study in this week's Journal of the American Medical Association shows doses of radiation given in some types of CT scans for heart disease are potentially harmful. The scans are frequently used to look for heart disease in people who don't have symptoms, and the researchers say the high radiation dose needlessly raises the risk of cancer for these patients.

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ROBERT SIEGEL, host:

From NPR News, this is ALL THINGS CONSIDERED. I'm Robert Siegel.

MELISSA BLOCK, host:

And I'm Melissa Block. CT scans of the heart have become more common in recent years. They are accurate tools to diagnose plaque in arteries leading to the heart, but the scans are not without risk. As NPR's Patti Neighmond reports, a study in the "Journal of the American Medical Association" raises questions about radiation levels associated with the scans.

PATTI NEIGHMOND: CT scans use a computer to combine hundreds of x-ray images and produce three dimensional pictures of the heart. Dr. Thomas Gerber is the cardiologist at the Mayo Clinic in Jacksonville, Florida.

Dr. THOMAS GERBER (Cardiologist, Mayo Clinic): It has to be quick because the heart moves all the time. And with a slow scanner, we wouldn't be able to freeze the motion of the heart and all we'd get is blurry images, like a car racing by on a photograph.

NEIGHMOND: The exquisitely detailed pictures help cardiologists, like Gerber, diagnose plaque build up in the heart without an invasive procedure, like an angiogram. So, it's no wonder CT scans of the heart have become popular.

Dr. GERBER: The images are so gorgeous, and the temptation to look at the heart arteries is so great, that we expect the use of cardiac CT to rise fairly steeply.

NEIGHMOND: Which is why Gerber and colleagues in Munich, Germany, decided to find out just how much radiation was used during CT scans. Researchers looked at nearly 2,000 patients who went to 50 different cardiac labs worldwide. They found a fairly wide variation in radiation dose. But, Gerber says, the average was significant.

Dr. GERBER: It's approximately four times the natural radiation dose that we all receive annually in the Unites States, as a result from background radiation due to radon and other materials.

NEIGHMOND: Even low-dose radiation can put patients at risk for cancer - that's why, Gerber says, doctors should be cautious when prescribing the scans.

Dr. GERBER: You're probably going to want to make that investment in a patient that truly has something to gain, and those would be the patients who already have signs or symptoms of heart (unintelligible) disease: Such as chest pain, or shortness of breath or exercise intolerance.

NEIGHMOND: Even people who have risk factors for heart disease like obesity, diabetes, high cholesterol or high blood pressure, shouldn't risk the radiation exposure, says Gerber, unless they have actual symptoms. In a related editorial, cardiologist Andrew Einstein, from Columbia University, says there are methods labs could take to reduce the amount of radiation in these scans.

Dr. ANDREW EINSTEIN (Cardiologist, Columbia University): Using beta-blockers or other medications to lower patient's heart rate, which in many cases will chip the radiation dose down by minimizing the number of images which are taken, and matching the technical parameters such that the patient doesn't receive too many x-rays.

NEIGHMOND: There is no federal regulation of radiation dose except for mammograms, which use much less radiation anyway. Dr. Einstein says clinics should not only scrutinize patients more closely for heart scans, they should also consider adjusting their scanning machines, or investing in newer machines that produce less radiation.

Patti Neighmond, NPR News.

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