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Because carotid artery disease usually has no symptoms, it can be a difficult disease to diagnose. In many cases, physicians may persue a diagnosis of carotid artery disease based on the number of risk factors a patient has. One leading risk factor is a family history of coronary artery disease or peripheral arterial disease. Thus, most physicians will begin the diagnosis by taking a complete medical history.
The physician will also ask questions about the patient’s smoking history and level of exercise, as well as other risk factors associated with carotid artery disease. Finally, the physician will ask if the patient has had any recent symptoms of a transient ischemic attack (TIA) or stroke.
Following the medical history, the physician will give the patient a complete physical examination. As part of this exam, the physician will listen to the patient’s carotid arteries through a stethoscope placed on the patient’s neck. Carotid artery disease will sometimes produce sounds called bruits (broo–EEZ), which is the French word for “noises.” However, different physicians interpret these sounds differently, and the sounds are not always present in patients with carotid artery disease. Therefore, a number of tests may be needed in order to make a diagnosis. These tests include the following:
- Carotid duplex imaging. Also known as a Doppler ultrasound of the carotid arteries, this noninvasive test uses high-frequency sound waves to create a moving image of the carotid arteries and to measure the speed at which blood is flowing through them. This test is highly accurate and should be the first diagnostic test for patients in whom the suspicion of carotid artery disease is high.
- Cerebral angiogram or digital subtraction angiogram (DSA). A catheter-based test in which a catheter is inserted through a blood vessel (usually the femoral artery in the groin) and up to the carotid arteries. A special dye (contrast medium) is inserted through the catheter and into the carotid arteries. Following the injection of this dye, very clear x-rays can be taken of the carotid arteries.
- Magnetic resonance angiogram (MRA). A minimally invasive test for creating three-dimensional images of the carotid arteries, revealing blood flow and detecting damage in the vessel walls. The test takes less time, requires a shorter recovery period and poses fewer risks than a cerebral angiogram. Currently, the image provided by an MRA is not as clear as the image produced by the more invasive cerebral angiogram. However, the clarity is improving through technological advances and the use of contrast agents delivered through a small intravenous catheter in the arm. The MRA is expected to become the principal diagnostic test for carotid artery disease in the near future.
- Computed tomography arteriography (CT-A). This is a relatively new technique that uses a CT scanner to generate pictures of the carotid arteries. This is nearly identical to a carotid angiogram except that the contrast medium is put into the veins instead of the arteries and therefore has a lower risk of complications. This has become the primary test in some locations and is very likely to have a much more prominent role in the future as a result of the high reliability and availability of CT scanners in the United States.
Advanced imaging techniques are also allowing physicians to better describe the characteristics of carotid plaque. For example, many researchers classify plaque as homogeneous or heterogeneous. Homogeneous plaque has a smooth surface and is basically the same texture throughout. Heterogeneous plaque has an irregular surface with areas of hemorrhage. Studies have found that heterogeneous plaque is the likely culprit among individuals who have had a stroke or TIA.
It is felt that therapy for carotid artery disease will eventually be influenced by such characteristics of carotid plaque, in addition to the degree of narrowing (stenosis) of the carotid artery.
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