Searching for Subclinical Atherosclerosis: Coronary Calcium Score-How Old Is My Heart?

Heart attacks and most sudden cases of sudden death are due to rupture of atherosclerotic plaques. Thus, it makes sense to seek out  such plaques, a process I call searching for subclinical atherosclerosis. I’ve talked about using high frequency ultrasound of the carotid arteries to the brain to look for plaque and for carotid IMT in earlier posts here and here.

There is a third method that looks directly at the coronary arteries, which supply blood to the heart.  It is variously called a heart scan, coronary calcium score, or cardioscan, and it is more widely utilized amongst physicians who are serious about preventing cardiovascular disease.

This technique utilizes the ionizing radiation inherent in X-rays to perform a CT examination of the chest. It does not require injection of any dye or the puncture of any arteries; thus, it is considered noninvasive and has no risk or pain associated with it.

When atherosclerosis first begins to form in the arteries, it generally takes the form of “soft” plaques. Soft plaques are initially full of lipids, but after a period of time, the plaques undergo change: calcium begins to deposit into this plaque.

There is a direct relationct_calciumship between coronary artery calcium (CAC) and the amount of atherosclerotic plaque in the coronary arteries.

CT scans are very accurate in identifying small amounts of calcium in the soft tissue of the body. Calcium score tests essentially look for blobs of calcium that are felt to be within the coronary arteries, count up the intensity and distribution of them, and calculate a total score that reflects the entire amount of calcium in the coronary arteries.

A large body of scientific literature has documented that higher calcium scores are associated with higher risk of significantly blocked coronary arteries and of heart attack.

You can read the NHLBI clinic’s info for patients here on the test.

How Is The Calcium Score Used To Help Patients?

The calcium score can be utilized (in a manner similar to the carotid IMT and plaque) to help determine whether a given individual has more advanced atherosclerosis than we would predict based on their risk factor profile. A score of zero is consistent with a very low risk of significantly blocked arteries and confers an excellent prognosis. On the other hand, scores of >400 indicate extensive atherosclerotic plaque burde , high risk of heart attack, and high likelihood of a significantly blocked coronary artery.

The calcium score (similar to the carotid IMT) increases with age and is higher in males versus females at any given age. We have very good data on age and gender normals. The average 50-59 year old woman has a zero score, whereas a man in that age range has a score of 30. The average man has developed some CAC by the fourth decade of life whereas the average woman doesn’t develop some until the sixth decade. More advanced CAC for age and gender is a poor prognostic sign. You can plug your own age, gender, race and CAC score into a calculator on the MESA (Multi-ethnic Study of Atherosclerosis) website here.

2013 ACC/AHA Guideline on the Assessment of Cardiovascular Risk says the following

 If, after quantitative risk assessment, a risk based treatment decision is uncertain, assessment of 1 or more of the following—family history, hs-CRP, CAC score, or ABI—may be considered to inform treatment decision making

This guideline recommended utilizing a  CAC score of >300 Agatson Units or >75th percentile for age, gender and ethnicity as a cut-off.

CAC Score Identifies Those At Very High  Risk

A forty-something year old man came to see me for palpitations. He had a stress echo which was normal except for the development of frequent PVCs and a brief run of non sustained ventricular tachycardia.  His risk factor profile was not particularly bad: no diabetes, hypertension, or cigarette smoking and an average lipid profile. When I calculated his 10 year risk of ASCVD using my iPhone app it came out at 7%: below the level at which statin treatment would be recommended.  Because his father had a coronary stent in his fifties (this does not qualify as a family history of heart disease according to the new guideline, by the way)  I recommended he get a CAC test done.

His CAC score came back markedly elevated, almost 1000.  .  A subsequent cardiac catheterization demonstrated a very high-grade coronary blockage iwhich was subsequently stented. I started him on high intensity statin therapy and he has done well.

CAC score identifies Those At Very Low Risk

Many individuals with high cholesterol values do not develop atherosclerosis.  A zero CAC score in a male over 50 or a woman over 65 (or non-zero CAC score that is <25th percentile for age, gender, ethnicity) indicates that they are not developing atherosclerosis and makes it less likely that they will benefit from statin therapy to lower cholesterol.

Some Caveats About CAC score testing

-Like carotid vascular screening, there is no reason to get a CAC test if you already have had problems related to blocked coronary arteries such as a heart attack or coronary stents or coronary bypass surgery.

-CAC score testing is not covered by insurance (except in Texas) and costs somewhere between $125 and $300 out of pocket.

-The CT scan leads to a small amount of radiation exposure-approximately 1 – 2 milliseiverts of radiation (mSv). To puts things in perspective, the annual radiation dose we receive from natural sources is around 3 mSV per year.

Some of the other approximate radiation doses for tests commonly used in medicine are:

Chest X-ray ( )            0.1 mSV
Routine CT chest:  10 mSV
CT abdomen: 10 mSV
Nuclear stress test: 10 to 20 mSV

24 thoughts on “Searching for Subclinical Atherosclerosis: Coronary Calcium Score-How Old Is My Heart?”

    1. I am unaware of any study demonstrating that. Atherosclerosis seems to be somewhat of a random and jerky process. For example, the left carotid can be totally free of plaque but the right have quite advanced plaque. When plaque progresses it likely occurs through a sudden process of rupture and healing rather than a slow , gradual accretion.

  1. Howdy, apologies for digging up an old thread, but I was wondering if you could elaborate on this point: ” -Like carotid vascular screening, there is no reason to get a CAC test if you already have had problems related to blocked coronary arteries such as a heart attack or coronary stents or coronary bypass surgery.”

    11 months ago it was found I had an 80% LAD stenosis, which was stented. Going forward, if I wanted to “monitor” how clean my stent and other areas of my heart remain, how else would I know if I’m developing buildup again? My total cholesterol at the time I received the stent was 101…HDL 34, so each quite low. Thoughts?

    1. :My point was that once you have established severe coronary disease ( heart attack, stent, bypass surgery) screening for premature atherosclerosis makes no sense.
      With regard to “monitoring” how “clean” your stent is:
      1. It is a question I get a lot .
      2. I hope to write a full post about it.
      3. A routine annual stress test is not a good idea (I’ve written on that”
      4. Coronary calcium is not helpful. Doesn’t tell you about % blockages
      5. Cath is risky and should not be repeated without other evidence of a problem
      6. Coronary. CT angiogram would be nice but is expensive, carries radiation exposure
      Ultimately, I closely monitor my patient’s symptoms and exercise tolerance looking for anything that might suggest a problem. If symptoms develop we do stress test.
      Most importantly you should be on high intensity statin therapy plus aspirin.

  2. After watching a 41 year old “healthy” man die of a heart attack on the basketball court in front of his kids I decided to do more research on the scan. In NY insurance doesn’t cover it but I have come across 2 places where I can refer patients. My question is, 1 place charges $99 and uses a 64 slice and the other charges $399 and uses a 160 scan. Is there a significant difference in these machines? Thanks

  3. Hi I am a 51 year old man I had a calcium score of 244 about a year ago I never smoked in my life but was always overweight and ate poorly since my rest I have lost 70 lbs lowered my ldl to 68 hdl is 42 triglycerides around 125 all other blood work is normal I now eat very healthy and exercise my ekg,echocardiogram, and treadmill stress test were all normal but my insurance company will not allow a nuclear stress test as they say my calcium score is moderate but judging by your calculations I am in the 94th percentile so how can that be normal I feel like I’m a ticking time bomb any input you have will be greatly appreciated thank you

    1. Even though your calcium score is very high for your age it is not in the range (>400) where we expect to see plaque in your coronaries obstructing blood flow. If you are active and have no symptoms there is no benefit to doing a nuclear stress test (especially with a normal treadmill stress ECG test.) Even if the nuclear test was abnormal there is no evidence that stenting or bypass would prevent heart attacks or prolong your life in this situation. Thus the results would not change the recommended treatment which is modifying the risks that brought on the plaque. Such treatment definitely involves the excellent lifestyle changes you have made. You might also consider taking at least a low dose statin because chances are you have inherited a tendency to build up plaque (see my post on dealing with the cardiovascular cards you”ve been dealt.)

  4. As a NP working in a primary care setting I wasnt aware of the CAC until I recently watched a documentary called “The Widow Maker”. I asked the MD that I work with about it and he informed me that he was familiar and had had one himself in the past. When I asked why he didn’t offer to his patients his response was ” insurance wont cover it”.
    After about a half a day of research I was able to find an imaging facility that would charge $99 for the test for direct referrals from our office. The test can cost anywhere from $350-$500 in NYC.
    Although our patient’s are of a lower income status many have chosen to pay the fee and have the test. At least now they have the option. I myself had the test done and it took all of 3 minutes. Im happy to report in my early 40s my score is 0

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