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The topic of coronary calcium scores has come up more and more lately in the media, as studies are reported documenting their use.
Just what is a "coronary calcium score" and what does it mean?
First of all, atherosclerotic plaque is the material that, over the years, can accumulate in various arteries of the body, but especially coronary (heart) arteries, carotid (neck), aorta, and the large iliac and femoral arteries of the pelvis and legs.
During most of the 20th century, there was no easy, safe, and inexpensive method to identify atherosclerotic plaque and screen people for the potential for heart attack (coronary artery atherosclerosis), stroke, (carotid and aortic atherosclerosis), or abdominal aneurysms (aortic atherosclerosis). That's why attention focused on the concept of "risk factors," identifiable factors that increased the likelihood of having atherosclerosis and thereby potential for heart attack and its other manifestations.
Thus, smoking and high LDL cholesterol were among the risk factors that, when present, increased the likelihood of having atherosclerosis, especially coronary. While helpful, risk factors always suffered from a fundamental limitation: They did not represent the disease itself, only a potential contributor to its cause. In other words, if we have a 50-year old smoker, do we know whether or not she has coronary atherosclerotic plaque? We do not, though we know that she has higher likelihood than a 50-year old non-smoker. If a 42-year man has an LDL cholesterol of 160 mg/dl, can we decide that he has atherosclerotic plaque in his coronary or carotid arteries based on this value? Once again, no we cannot, though the statistical likelihood of having atherosclerosis in those arteries is greater than another 42-year man with LDL cholesterol of 120 mg/dl.
The quest to develop a screening tool not just for risk factors, but for the disease of atherosclerosis itself, has therefore been underway for several decades. If you have atherosclerotic plaque, you have the disease. If you have a little bit, you have less potential for stroke or heart attack compared to someone with a lot. Thus, quantification is an important aspect of atherosclerosis detection.
That's where coronary calcium scores come in. Of all the ingredients contained in atherosclerotic tissue-inflammatory cells, cholesterol and other fats, structural tissue, and calcium-it's the calcium that can be readily visualized in the coronary arteries. It can also be quantified.
Dr. John Rumberger, while at the Mayo Clinic in the 1990s, made a crucial observation. He determined that, while the presence of calcium up until then had been considered nothing more than a curiosity, even an annoyance since it sometimes got in the way when performing procedures like stent implantation, calcium was present in a reasonably consistent proportion to the other components of plaque, always occupying 20% of the volume. (He and his team determined this by examining coronary arteries of people who had died.) In other words, measuring 2 mm3 of calcium meant that there was 10 mm3 of total atherosclerotic tissue.
