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February 2, 2007
February 2, 2007
Physicians at the University of Chicago Medical Center are now offering a screening test using ultrasound images of arteries in the neck to assess the future risk of heart attack or stroke. The test also allows an estimation of the typical age of someone with similar blood vessels.
Heart specialists have used the test, known as carotid intima-media thickness, or CIMT, for more than a decade in large research studies to monitor the effects of exercise, diet or medications on the progression of atherosclerosis. Now, using data accumulated from thousands of patients followed during such studies, physicians can estimate the risk of a major cardiovascular event--such as a heart attack or stroke--by taking precise measurements of the thickening of the easily accessible carotid arteries, which pass near the surface through the neck.
"The standard risk factors--increased age, smoking, cholesterol levels, high blood pressure, diabetes--affect the arteries throughout your body, in much the same way as they affect those that supply your heart," said cardiologist Parker Ward, M.D., assistant professor of medicine at the University of Chicago. "By measuring the thickness of the first two layers of your carotid artery, we can get a pretty accurate estimate of your risk of cardiovascular disease."
The results are reported to patients in a chart that shows how their vessels compare with others of a similar age and gender. A 50-year-old patient with treated high blood pressure and high cholesterol, for example, who exercises, doesn't smoke and sticks to a healthful diet, may have blood vessels typical of a 43 year old. But another patient, also 50, who smokes, is overweight and has a family history of heart disease, may have vessels as thick as a typical 65 year old.
Thickening of an artery provides the earliest easily detectible anatomical evidence of atherosclerosis (hardening of the arteries). In this test, physicians use sound waves to measure the width of the two inner layers of the carotid artery: the intima and the media. Common carotid artery intima-media thickness ranges from about 0.5 millimeters in a healthy young person to 1.5 millimeters in an older person with advanced cardiovascular disease.
"A thicker CIMT is associated with all the major cardiovascular risk factors, is significantly correlated with coronary artery disease and is highly predictive of future cardiovascular events," Ward said. "The greater the CIMT value, the greater the likelihood of a heart attack or coronary death, or stroke"
According to the American Heart Association Prevention Conference V Statement on CIMT, this is a "safe, noninvasive, and relatively inexpensive means of assessing subclinical atherosclerosis....The severity of carotid CIMT is an independent predictor of transient cerebral ischemia, stroke, and coronary events such as myocardial infarction."
The technique, according to a recent (2002) review article, provides a "comprehensive picture of the alterations caused by multiple risk factors over time on arterial walls. Close relationships," the review states, have been shown between CIMT and most traditional cardiovascular risk factors, certain emerging risk factors and cardiovascular damage.
CIMT is appropriate for patients without symptoms but with traditional risk factors for heart disease identified on routine physician visits--such as a family history of cardiovascular disease, high blood pressure or high cholesterol levels--to prompt lifestyle changes or possibly medications to modify these risks. Among patients with existing cardiovascular disease, serial studies can be used to monitor the blood vessels' response to lifestyle and medication changes.
"Atherosclerosis often remains 'silent' for many years," Ward said. "In about half of patients who present with heart disease, the first clinical manifestation is a heart attack or sudden cardiac death. Traditional risk factors should always be first step in identifying patients at risk, but among those with risk factors, clinical CIMT testing may provide an additional option to patients and physicians to identify those patients at the highest risk."
While CIMT is recognized as a valid, safe and non-invasive means for assessing cardiovascular disease, the test has only recently begun to move from the research arena to clinical application. It is not yet widely recommended to patients for screening. Medicare and most private insurance will not routinely pay for the CIMT test at this time.
The University of Chicago Medical Center provides this safe and non-invasive exam for $339.