Carotid ultrasound: a test for heart disease?
If you wanted to find out whether you had hidden heart disease, just how would you go about it?
Carotid ultrasound is test that some individuals advocate as an indirect means of detecting hidden heart disease. While not perfect, it can be an interesting way to gauge your future potential for heart disease and early enough to take effective preventive action.
Using high-frequency sound, clear images of the carotid arteries (the two arteries on either side of the neck) are available for virtually all people. The carotid arteries are a bit unusual in that they are very close to the surface of the body. Carotid arteries develop atherosclerosis that put us at risk for stroke. But they also provide a gauge of atherosclerosis that could be present elsewhere. That dual role makes ultrasound of the carotid arteries a highly useful test. In particularly, examination of the carotid arteries can provide an index of disease that might be present in the heart's coronary arteries that cause heart attack.*
Carotid ultrasound is easy, safe, and available in most hospitals and even many clinics. No radiation is involved. One difficulty: most insurance companies will not allow you to go through a carotid ultrasound scan as a "screening" procedure, i.e., a test just to see if you have a carotid plaque. They will generally pay (in typical insurance company fashion) if you're having symptoms of a stroke or "mini-stroke" (transient ischemic attack, or "TIA"), have an abnormal sound in your carotid ultrasound detected by your doctor (a carotid "bruit"), or some other unusual indications. Sometimes, a resourceful physician will muster up a diagnosis based on something in your history (e.g., left arm numbness, feeling faint, etc.).
Other options are the mobile scanners and some hospitals that offer carotid screening, usually for a very modest price, usually less than $200 (even occasionally for free) for a combination of carotid ultrasound, ultrasound of the abdominal aorta to screen for aneurysms, and bone density testing. Drawback: Sporadic availability, difficulty in obtaining serial scans, and imprecise reporting since it's viewed as a screening test. But it's a lot better than nothing.
My hope is that, as screening services using safe imaging techniques like ultrasound propagate and increase in direct availability to the public, you'll be able to circumvent the obstacles imposed by your insurance company and even, sometimes, your doctor. But try your doctor first.
I say carotid ultrasound is not perfect because the way it's done in 2008 makes it a non-quantitative test. It is a qualitative test. In other words, you may find out that there's a 30% blockage ("stenosis"), at the far end of the common carotid artery on the right side, but, in truth, that figure is an estimation, given the methods used to measure plaque in the carotid artery (much of which relies on velocity of flow in the arteries). It does, however, suggest several important facts to you and your doctor: First, one or more factors in your lifestyle or genetics allows the development of atherosclerosis. Second, unless you and your doctor take effective preventive action, a stroke could be in your long-term future. Third, coronary atherosclerotic plaque (i.e., coronary disease) is likely present to some degree. Investigating this possibility may be necessary, along with preventive efforts.
Followers of my blog posts know that I am a vocal advocate of CT heart scans (not to be confused with CT coronary angiograms, the test that has lately been the subject of news reports discussing the high radiation exposure associated with these tests). If you have access to a heart scan, that's the best way to go. It's a direct and accurate detector of hidden coronary atherosclerosis. If you don't have access to a heart scan, carotid ultrasound can serve as a second best. Even better, get both tests and have direct gauge of these terribly common diseases-hopefully years before danger is present and preventive efforts can pay off with big rewards.
*Now that much of the public is going straight to the medical literature for in-depth medical information, it's important to clear up a common point of confusion. There is a measure obtainable with carotid ultrasound called "carotid intimal-medial thickness," or CIMT. This is a measure of very early carotid atherosclerosis, a measure of the thickness of the tissue-like lining of the artery that thickens even before early blockages are present. For example, a 30% blockage would ordinarily be regarded as an "early" blockage. However, CIMT will be abnormal years before the 30% blockage is even present. Unfortunately, it is rarely performed in clinical ultrasound laboratories.
CIMT is the measure often used in research studies that is an accurate gauge of atherosclerosis in other arteries like the coronaries. However, in real-life clinical practice, CIMT is rarely measured and most ultrasound facilities are not set up to perform it.