Intimal-Medial Thickness (IMT) Test
Ultrasound scanning to detect and quantify the amount of thickening
The identification of patients at risk for heart attack and stroke is of great concern for a physician. There are now several "imaging" tests that can supplement our ability to detect the presence of atherosclerotic plaque in the carotid and coronary arteries.
The measurement of Intimal-Medial Thickness (IMT) in the carotid arteries (in the neck) is a painless test that utilizes ultrasound scanning to detect and quantify the amount of thickening just below the inner lining of the carotid artery.
The Carotid IMT test uses state-of-the-art ultrasound technology and FDA approved software to measure the thickness of the first two layers of the carotid arteries located in the neck, where blood-flow-blocking plaque first develops. Abnormal, premature thickening of the arterial walls is an early indicator of vascular disease throughout the body. The thicker the arterial wall, the greater the risk for heart attack or stroke. No other test available can measure these silent, early changes as accurately as high-resolution ultrasound imaging used together with the IMT measuring software.
The test is a simple, non-invasive, 15-20 minute outpatient procedure that involves no pain, no needles, no pills, and exposes you to no radiation. During the test, you lie flat on an exam table for approximately 15 minutes. A small amount of gel is applied to your neck and sound beams are used to look at the thickness of your carotid arteries and for plaque formations. The test uses sophisticated ultrasound equipment, stringent test examination standards, and requires expert interpretation, so it's not widely available.
Why look at the neck when you are interested in the heart?
The carotid arteries provide a "window" to the coronary arteries.1Not only do they have similar risk factors - more importantly, the relationship between the atherosclerotic burden in a carotid artery and a coronary artery is the same as between any two coronary arteries. Thus, carotid atherosclerosis provides a window to the degree of coronary atherosclerosis in an individual. By examining the carotid artery wall rather than the blood pathway itself, risk prediction with carotid ultrasound identifies an earlier stage of atherosclerosis than standard Duplex carotid imaging, or any other imaging test for that matter.
Using a high-resolution B-mode ultrasound transducer, the common carotid, the carotid bulb, and the internal carotid artery can be interrogated to identify the presence of non-obstructive plaques and specifically to measure Carotid IMT, the combined thicknesses of the intimal and medial layers of carotid walls. Carotid IMT is an independent predictor of future cardiovascular events, including heart attacks, cardiac death, and stroke.
1Young W, Gofman J, Tandy R, Malamud N, Waters E. The quantitation of atherosclerosis III. The extent of correlation of degrees of atherosclerosis with and between the coronary and cerebral vascular beds. Am J Cardiol 1960;8:300-8.