By Julie Bromberg
Heart disease is the leading cause of death among adults in the U.S., so some doctors have recently started using Computed Tomography (CT scanning, or “CAT scan”) to detect blockages in the heart’s arteries that can cause heart attacks. Unfortunately, a CT scan uses relatively large doses of radiation-an average heart CT scan exposes a patient to 23 times as much radiation as a chest x-ray.[end U.S. Department of Energy, Office of Biological and Environmental Research, Office of Science, Ionizing Radiation Dose Ranges. March 2006. Available at: http://lowdose.tricity.wsu.edu/resources_pics/images/026_dose-ranges-sievert.jpg][end Kim KP, Einstein AJ, and de Gonzalez AB. Coronary Artery Calcification Screening: Estimated Radiation Dose and Cancer Risk. Archives of Internal Medicine, July 13, 2009; 169(13): 1188-1194.]
Researchers warn that if this test is widely used, we could see many new cases of cancer from increased exposure to radiation.
Doctors usually decide if a patient has a high or low risk for heart disease by assessing the person’s “risk factors” for heart disease. A “risk factor” is a behavior or characteristic that makes it more likely that a patient will get a certain disease.
People who have a higher risk of heart disease have some of the following risk factors:
- unhealthy diet,
- smoke tobacco,
- high cholesterol,
- high blood pressure,
- older age, and several other risk factors
Patients with these high risk factors are more likely to have blocked or narrowed arteries, which can prevent blood flow and are a major cause of heart attacks and strokes. Doctors often recommend medication to people who have a high risk of heart disease, in addition to lifestyle changes such as healthier diet, exercise, and quitting smoking, which can help everyone prevent heart disease.
Even with information about cholesterol and blood pressure, however, doctors cannot always predict who will have blocked arteries. Some people who appear to be at low risk (for instance, non-smokers with low cholesterol) may have a build up in their arteries and could suffer from a heart attack. The heart CT scan has the advantage of detecting blockages in patients who seem to have a low risk of heart disease. One preliminary analysis found that the heart CT scan could prevent 9,000 more deaths than doctors’ traditional way of assessing risk factors,[end Diamond GA and Kaul S. The Things to Come of SHAPE: Cost and Effectiveness of Cardiovascular Prevention. The American Journal of Cardiology, April 2007; 99(7):] while other studies have found that CT scanning does not actually improve health outcomes.[end Waugh N, Black C, Walker S, McIntyre L, Cummins E, and Hillis G. The Effectiveness and Cost-Effectiveness of Computed Tomography Screening for Coronary Artery Disease: Systematic Review. Health Technology Assessment, 2006; 10(39): iii-iv, ix-x, 1-41.][end Gibbons RJ and Gerber TC. Calcium Scoring with Computed Tomography: What is the Radiation Risk? Archives of Internal Medicine, July 13, 2009; 169(13): 1185-1187.]
The American Heart Association, American College of Cardiology, and the United States Preventive Services Task Force do not recommend the use of heart CT scans for patients with a low or high risk of heart disease because CT scans could be more harmful than beneficial due to the relatively high dose of radiation.[end Bluemke DA, Achenbach S, Budoff M, Gerber TC, Gersh B, Hillis LD, Hundley WG, Manning WJ, Printz BF, Stuber M, and Woodard PK. Noninvasive Coronary Artery Imaging Magnetic Resonance Angiography and Multidetector Computed Tomography Angiography: A Scientific Statement From the American Heart Association Committee on Cardiovascular Imaging and Intervention of the Council on Cardiovascular Radiology and Intervention, and the Councils on Clinical Cardiology and Cardiovascular Disease in the Young. Circulation, July 2008; 118: 586 – 606.][end Barclay L. SHAPE Task Force Recommends Noninvasive Cardiac Screening for Asymptomatic Adults. Medscape Medical News, July 13, 2006.]
In contrast, the Screening for Heart Attack Prevention and Education (SHAPE) guidelines recommend that heart CT scans be used to detect blockages in arteries of older men and women who do not have symptoms of heart disease. SHAPE’s guidelines lack scientific support, however, and although well-respected doctors helped write the guidelines, SHAPE is funded by several drug companies that could profit from increased use of heart CT scanning.
If doctors follow SHAPE’s recommendation, tens of millions of adults would be exposed to relatively high levels of radiation through this procedure. Doctors still have not established a standard dose of radiation to be used for heart CT scans and doses for this test vary from one hospital to another, with some patients getting 10 times the amount of radiation as patients in another hospital. A recent study estimated that one heart CT scan for the 50 million Americans who would be affected by SHAPE’s guidelines could cause 2,700-37,000 new cancer cases, depending on the dose of radiation. (Assuming the average radiation dose, these scans could result in 5,600 new cancer cases). The number of new cancer cases could be even higher if individuals were screened more than once in their lifetime.[end Kim KP, Einstein AJ, and de Gonzalez AB. Coronary Artery Calcification Screening: Estimated Radiation Dose and Cancer Risk. Archives of Internal Medicine, July 13, 2009; 169(13): 1188-1194.]
Radiation from CT scans is of concern to the FDA even when the CT scans are necessary. On October 9, 2009, the FDA announced that it was notifying healthcare professionals that 206 patients who were being tested for stroke received CT radiation doses that were approximately eight times the expected level at one particular medical facility. While this event involved a single kind of diagnostic test at one facility, the FDA warned that “it may reflect more widespread problems with CT quality assurance programs.”
Each year, over 600,000 Americans die from heart disease even though heart disease can be prevented.[end Kung HC, Hoyert DL, Xu J, and Murphy SL. Deaths: Final Data for 2005. National Vital Statistics Reports. 2008;56(10).] Although heart CT scanning may be a useful tool in detecting blockages in heart arteries, there is not enough evidence to show that this test is worth the risks, especially compared to traditional risk factor assessment.[end Waugh N, Black C, Walker S, McIntyre L, Cummins E, and Hillis G. The Effectiveness and Cost-Effectiveness of Computed Tomography Screening for Coronary Artery Disease: Systematic Review. Health Technology Assessment, 2006; 10(39): iii-iv, ix-x, 1-41.][end Gibbons RJ and Gerber TC. Calcium Scoring with Computed Tomography: What is the Radiation Risk? Archives of Internal Medicine, July 13, 2009; 169(13): 1185-1187.]
11] For this reason, the Cancer Prevention and Treatment Fund of the National Research Center for Women & Families agrees with the U.S. Preventative Services Task Force that heart CT scans are not recommended for screening for heart disease. And, we agree with the FDA that doctors need to ensure that the risks of radiation from CT scans do not outweigh the benefits of testing.
There are several safer steps you can take to prevent heart disease:
- Eat healthy foods
- Stop smoking
- Reduce your stress as much as possible
If you have high cholesterol and/or blood pressure, talk to your doctor about how to manage it.