by wmodavis » Thu Aug 11, 2011 11:25 pm
I'm with you on most of that Lars.
There are disadvantages to all those ways you mentioned to measure actual plaque. In short they do not do a good job of that. Using a coronary artery calcium does a much better and more accurate job of that. It is the best technology today for determining if you have plaque. It's a bit like using a stress test to determine your risk of a heart attack. It simply won't tell you that. Here is an exerpt from Dr
William Davis's book "Track Your Plaque" wherein he discusses the other ways to proportedly measure plaque.
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From Chapter 4
"Other methods to detect early heart disease:
Though imaging technology is advanced rapidly, many methods are not yet ready for mainstream use. There are several alternatives, however, to coronary calcium scoring using EBT or MDCT scanners that are already available. Let’s discuss these alternatives and their strengths and weaknesses.
[b]Carotid Ultrasound [/b]
Atherosclerosis is a body-wide disease that affects all arteries of the body. That means plaque can develop simultaneously in the heart (coronary arteries), the brain (carotid arteries and cerebral circulation), the abdomen (abdominal aorta and mesenteric arteries), legs (iliac and femoral arteries), etc. Plaque develops in these parts of the body in parallel to the heart, though to varying degrees.
Most people with atherosclerotic disease tend to show evidence of disease in their heart first, i.e., they have a heart attack, or develop angina, or undergo a cardiac procedure. The other arteries of the body, though also developing plaque, tend to do so more slowly. This is partly due to the larger diameter of other arteries. Compare their relative sizes: coronary arteries generally measure 3–4 mm in diameter; carotid arteries measure 5–8 mm; femoral (thigh) arteries measure 6–9 mm, sometimes larger. Less plaque accumulation is, therefore, required in the smaller heart arteries before trouble ensues.
Nonetheless, because there is a parallel tendency for various arteries to develop plaque, some physicians have proposed that other arteries be measured in place of the heart. The imaging technique usually used is ultrasound, since it is easy, painless, and can be somewhat quantitative.
In ultrasound (like that used for intracoronary ultrasound), images are generated by a high-frequency sound-emitting crystal. The data is processed by a computer and converted into images. The best-studied technique involves ultrasound imaging of the carotid arteries, in which the device is applied gently to the neck and the carotid arteries (right and left) are examined. Using this technique, a measure called carotid intimal-medial thickness (CIMT), or the thickness of the internal lining of the arteries, is obtained. Note that CIMT is a measurement of the lining of the artery, not of carotid plaque itself. There have also been studies examining other arteries of the body (particularly the abdominal aorta, iliac, and femoral arteries), but they correlate less well to heart disease than the carotids.
Among the most experienced in this technique is Dr. Howard Hodis of the University of Southern California. His extensive experience does indeed suggest that measuring CIMT can predict heart attack risk, is correlated to a moderate degree with the extent of coronary plaque, and can be used to track the course of disease, i.e, progression or regression (Hodis HN 1996). CIMT measurement has been quite popular in research settings to examine the efficacy of various therapies.
Ultrasound is safe, since no radiation is involved. Devices capable of obtaining quality images are also very widely available. Most hospitals and even many cardiologists’ offices will have at least one if not several ultrasound units. Carotid ultrasound is already routinely performed to look for large plaques that pose risk for stroke.
So why isn’t carotid ultrasound performed more widely for identification of early heart disease?
There are several reasons. One reason is that the relationship of coronary disease to carotid IMT is not perfectly parallel. Coronary and carotid arteries respond somewhat differently to various influences and so develop plaque at different rates. Carotid IMT, for instance, is very sensitive to blood pressure effects; coronary plaque less so. The correlation of carotid IMT to coronary plaque is around 60 to 70%, meaning that a certain carotid IMT measurement will be around 60–70% accurate in predicting the extent of coronary plaque (Folsom AR 2008). It would be like buying a used car and trying to gauge the accuracy of the odometer mileage by looking at the wear on the rubber of the gas pedal—you can make relatively crude predictions, but it’s not terribly accurate.
Despite wide availability of ultrasound devices and the relative ease of obtaining this measure, the vast majority of facilities do not offer CIMT. CIMT measurement requires special software that most facilities do not have. Insurance also does not pay for CIMT. Ultrasound facilities, however, can measure carotid plaque, though in a non-quantitative way. Anyone who has undergone a conventional carotid ultrasound has likely been provided the frustratingly imprecise results, e.g., “10-49% plaque in the right internal carotid artery.â€