Should I Have A Coronary Calcium Scan?

CT scan
Calcium Scan. Reproductions Ltd/Getty Images

Q. My doctor has recommended that I get a cardiac calcium scan. I am a 52-year old man. I am a little overweight and don’t get much exercise, but my blood pressure and cholesterol are normal. (Well, my blood pressure is actually a little high sometimes, but only because I have two teenagers.) He did a stress test last year because I had some pain, but the pain turned out to be from heartburn. He says if the calcium scan is positive he’ll want me to take a statin. This I do not understand. Why look for heart problems when my stress test was OK? Is getting a calcium scan really a good idea? - T.L.

A. Here’s a general rule about the advisability of doing any medical test: It is reasonable to perform a medical test whenever the results of that test will be useful in making a decision about your medical care. In your case, your doctor would use the results of the calcium scan to decide whether or not to prescribe statin therapy.

So the short answer to your question is that your doctor’s recommendation to do a calcium scan is a reasonable one. Here is a more detailed answer, and I hope, a more useful one:

What Does The Calcium Scan Tell You About Your Heart? 

A cardiac calcium scan is a specialized CT scan that detects calcium deposits in the coronary arteries (the arteries that supply blood to the heart muscle). Calcium deposits occur in the arteries during the formation of atherosclerotic plaques.

Therefore, the presence of calcium deposits means that the disease process of atherosclerosis is present.

The reason atherosclerotic plaques are important is that these plaques tend to rupture. Plaque rupture is often accompanied by the sudden formation of blood clots in the artery at the site of the rupture, leading to sudden occlusion of the artery.

This event is called acute coronary syndrome (ACS). ACS most often causes at least unstable angina, or worse, myocardial infarction (heart attack).

So: if you have calcium in your coronary arteries, you already have atherosclerosis, and you are at risk for ACS.

The calcium scan not only tells you whether (yes or no) you have calcium deposits, but it also measures the extent of the calcium deposts, and reveals which of the coronary arteries are involved.

This information is summarized in a calcium score:

  • 0 - no identifiable disease
  • 1 to 99 - mild disease
  • 100 to 399 - moderate disease
  • 400 or higher - severe disease

The higher the calcium score, the more atherosclerosis is present in the coronary arteries, and the higher the risk of experiencing ACS over the next several years. But, importantly, any score higher than zero means that the disease process of atherosclerosis is already present, and to at least some extent, is active.

What Does The Calcium Score Really Mean?

When cardiac calcium scans were first commercialized and marketed in the early 2000s, they were surrounded by controversy. The controversy was partially related to the cheesy commercials that were produced to advertise them, but was mostly related to the fact that, at the time, the usefulness of these scans was poorly understood.

In that long-ago era, most cardiologists were only interested in atherosclerotic plaques that were large enough to cause significant obstruction in the coronary arteries. And the calcium scans are not particularly good at identifying which plaques are causing the dreaded “50% blockages” that (it was thought) ought to be treated with stents. The stress test was regarded back then as a far better screening tool for such “significant” blockages.

Since that time we have learned a lot about plaque rupture. It turns out that most cases of ACS occur with the rupture of “nonsignificant” plaques - plaques that were not causing significant blockage, and would not have been candidates for stenting. This means two things. First, while stenting significant blockages may relieve any angina being produced by those blockages, it often does not greatly reduce the risk of subsequent heart attacks. Second, it turns out that long-term cardiac risk is more nearly related to the overall “plaque burden” (that is, the number and extent of plaques of any size in the coronary arteries), than it is to the presence or absence of specific “significant” plaques.

Arguably, another name for plaque burden is the calcium score. Indeed, studies have now clearly shown that the higher the calcium score, the higher the subsequent cardiac risk, whether or not any of the plaques themselves are causing significant blockages.

What Should Be Done About A Positive Calcium Scan?

To summarize, the calcium scan tells you whether or not you have atherosclerosis in the coronary arteries, and if so, the extent of the atherosclerosis. If the calcium score is higher than zero (which, again, means that at least some atherosclerosis is present), some cardiologists will still then recommend a stress test, which will help them decide whether any of the plaques are causing significant blockages. But this, as we have seen, is not really the major point anymore.

The major point is whether or not you have atherosclerotic plaques. And if you do - if your calcium score is higher than zero - it becomes very important to do everything you can to reduce the risk, not only of developing further plaques, but also of plaque rupture.

Obviously, lifestyle choices that help prevent the progression of atherosclerosis would then become critical. Weight control, getting plenty of exercise, not smoking, and controlling blood pressure and cholesterol levels, all ought to be considered more as matters of life and death than they might have been before you knew that you already have atherosclerotic plaques.

Statins also become useful if your calcium scan is positive - even if (as in your case, my dear T.L.) your cholesterol levels are not elevated. This is because statins help to stabilize plaques, and help to prevent them from rupturing. This, and not their ability to reduce cholesterol, now appears to be the chief mechanism by which statins reduce cardiac risk. Taking low-dose aspirin every day may also become a consideration if your calcium scan is positive. (You should discuss this with your doctor, T.L., especially in light of your history of heartburn.)

So the bottom line is that it sounds as if your doctor is making a very reasonable recommendation when he advises a cardiac calcium scan, and it is one you should very seriously consider.

Sources:

Greenland P, Alpert JS, Beller GA, et al. 2010 ACCF/AHA guideline for assessment of cardiovascular risk in asymptomatic adults: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines. J Am Coll Cardiol 2010; 56:e50.

Budoff MJ, Shaw LJ, Liu ST, et al. Long-term prognosis associated with coronary calcification: observations from a registry of 25,253 patients. J Am Coll Cardiol 2007; 49:1860.

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