At the radiation dose levels used in cardiac imaging exams, such as cardiac CT or nuclear medicine scans, the risk of potentially harmful effects from ionizing radiation are low.
However, since the exact level of risk is not known, people without symptoms of heart disease should think twice about seeking, or agreeing to, these types of cardiac studies. This is the conclusion of an advisory committee convened by the American Heart Association's Council on Clinical Cardiology and Council on Cardiovascular Radiology and Intervention. A Mayo Clinic cardiologist led the committee.
In the Feb. 2 online issue of the journal Circulation , the panel says that cardiac scans that use ionizing radiation should, in all cases, be used judiciously, and are not recommended for people without chest pain or other symptoms who are at low risk for heart disease.
"There is a false sense of security among physicians that the radiation dose received by individual patients, and the potential health risks that may come with it, can be determined precisely," says Thomas Gerber, M.D., Ph.D., a cardiologist at the Mayo Clinic campus in Florida.
The uncertainty, and long-standing controversy, centers on how to connect the low doses of ionizing radiation received by patients from medical imaging procedures to the possibility of cancer development, says Dr. Gerber.
"There is no question that large doses of radiation, such as from the atomic bomb blasts in Japan, are linked to cancer, but there is a lot of unresolved debate about whether or not, or to what degree, low doses carry cancer risks," he says.
This issue is important in cardiology, Dr. Gerber adds, because cardiac CT imaging has become very popular and is being heavily marketed directly to the public. These scans can reveal whether a person's heart arteries have plaque in them. Yet, while these devices produce "stunningly beautiful images," Dr. Gerber says, "it has not been proven that detecting plaque at an early stage will allow doctors to make decisions that help their patients live longer."
In 2006, cardiac CT accounted for only 1.5 percent of the total dose to the U.S. population from CT. "We expect that the amount of radiation exposure attributable to CT imaging of the heart will rise rapidly as the technology improves and becomes more readily available," says Dr. Gerber. "However, the benefit of performing these scans in patients without symptoms is still unclear, and patients should know that."
On the other hand, the authors say that use of appropriate diagnostic imaging studies, such as cardiac CT, fluoroscopy, and nuclear medicine studies, should not be avoided in patients with symptoms of heart disease just because of concerns regarding radiation dose. "If a person has symptoms, the benefit of using these tests to come up with a treatment plan outweighs the small potential risk," Dr. Gerber says.