WHAT IS CAROTID IMT ?
The carotid arteries are found in the neck and supply blood to the brain. These arteries are large and lie just beneath the skin, allowing easy visualization through ultrasound scanning.
The intima and media are the layers that line the artery. With increasing age and with the presence of certain risk factors (such as high cholesterol, high blood pressure, smoking, obesity, diabetes) cholesterol become deposited in these layers. This increases the thickness of the inner layers which can lead to narrowings and even complete blockage. The thickening also leads to an increased risk of blood clots forming within the blood vessel.
Changes in the carotid artery reflect changes in other arteries found in various organs. It is presently not possible to easily see the heart arteries without more complex testing. The measure of carotid IMT is therefore an easy and safe way to find out the health of arteries throughout the body.
HOW THICK IS THICK ?
In multiple studies, carotid IMT has been shown to be a predictor for future heart attacks and stroke. An increase in thickness of just 0.1 mm actually increases risk for these illnesses by 11%. In particular, a thickness that is greater than 1 mm doubles the chance of developing a heart attack or stroke in the next 6 years.
Persons without known heart disease but have increased thickness would therefore benefit from aggressive treatment of risk factors to prevent the onset of both stroke and heart attacks.
HOW IS IT DONE ?
Ultrasound is a safe imaging technique that uses no radiation. A person is asked to lie down and a colorless gel is applied to the neck. A scanner is applied with moderate pressure over the neck. The scanner is slowly brought up and down the neck to scan the entire length of the carotid artery. Thickness of the intima-media is measured and the flow rate of blood passing through the artery is also measured. The entire study usually takes less than 20 minutes.