There is a growing acknowledgment of newer and more effective methods for detecting cardiovascular plaque. One of these techniques is the coronary calcium score.
What is the Coronary Calcium Score?
Coronary calcium score measures calcium in arteries using CT (computed tomography) imaging. The principle here is that any detected calcium signifies plaque or atherosclerosis (plaque build-up).
Coronary calcium score is known by other names: coronary artery calcium score or CACS; coronary calcium scan; coronary CT calcium scan; cardiac calcium scoring; or simply calcium score.
Coronary calcium score is an excellent screening tool. It’s easily accessible, inexpensive, and well-standardized.
However, it’s not a good test for tracking progress or change. There’s also the downside that a calcium scan only detects hard, calcified plaque, not soft plaque. There’s also the issue of a radiation risk.
How Coronary Calcium Score Works
The coronary calcium score starts as an image.
In CT imaging of coronary arteries, calcium would show up as bright, white areas. These white areas would be calculated, added, and expressed as a calcium score.
Examples of coronary calcium scans. Source. Princeton Longevity Center. Cardiac Scans.
With calcium scores, it’s possible to compare several instances (like before and after a cardiovascular event or introducing lifestyle changes), patients, and populations.
The premise is that the higher the score, the more calcium there is, the higher the risk of a future heart attack or stroke.
The Agatston Score
There are several coronary calcium score guidelines, with the Agatston score as perhaps the most popular.
The Agatston score was developed in 1990 by Dr. Arthur Agatston, the author of “The South Beach Diet” book series. According to Dr. Agatston:
We developed the calcium score, which is a way to image arteriosclerosis in your coronary arteries many years before it causes a heart attack or stroke. When we know it’s there, we can take steps to find out why it’s building up. And then choose our therapy.
Here’s a sample table of Agatston scores. It has 5 categories, ranging from 0 to over 400, with ranges connected to a risk level. Using the table below, if a person has a calcium score over 1,000, he/she is supposed to be in the high-risk category.
Agatston score. Rio Grande Hospital. Heart Scan (Coronary Calcium Scan).
What is a Normal Calcium Score?
Ideally, we’d like to have it at 0 or as low as possible.
Note, though, that many factors (including age and gender) have a say on calcium scores. To give you further ideas, here’s a sample distribution of calcium score by age in men…
Calcium Score Distribution in Men. Source: Casandra. CT Scan Calcium Score Range.
…and women.
Calcium Score Distribution in Women. Source: Casandra. CT Scan Calcium Score Range.
From the 2 graphs above, you’ll notice that women appear to be better in terms of calcium scores.
Agatston Scores vs. MESA
Agatston and other traditional calcium scoring methods indexed many populations to come up with their systems.
Unfortunately, they include incorrect assumptions about arterial calcification. They don’t account for calcium in all vascular beds. They also use outdated technology.
Such things have implications in defining a zero or low score. For instance, the technology misses soft, non-calcified plaque. Soft plaque is more dangerous than calcified plaques, as they are vulnerable to rupture and/or erosion.
Despite such issues, scientists continue to test alternative methods to mitigate calcium score’s weak spots.
Take the Multi-Ethnic Study of Atherosclerosis (MESA) as an example, which upheld the usefulness of calcium scoring but added improvements. The study gave rise to the coronary calcium score calculator, which combines calcium score and traditional risk factors (e.g., demographics, cholesterol, systolic blood pressure, diabetes, smoking, family history of cardiovascular heart disease, and the use of hypertension or cholesterol medications).
Here’s a sample comparison of how Agatston scores would fare against adjusted scores by MESA:
Agatston scores vs. MESA. Source: Casandra. CT Scan Calcium Score Range.
Supporters of coronary calcium score continue to increase over the years. There’s the Early Identification of Subclinical Atherosclerosis by Noninvasive Imaging Research (EISNER) trial, which was able to show a reduction in overall cardiovascular risk without the added cost by using calcium testing.
There’s also the 2018 ACC/AHA Cholesterol Guideline which recommends the use of calcium score:
…coronary artery calcium (CAC) testing may be considered in adults 40-75 years of age without diabetes mellitus and with LDL-C levels ≥70 mg/dl-189 mg/dl at a 10-year atherosclerotic cardiovascular disease (ASCVD) risk of ≥7.5% to <20% (i.e., intermediate risk group) if a decision about statin therapy is uncertain. (Blankstein, 2019)
The Calcium Score Paradox
The relationship between calcium, plaque, and cardiovascular risk is a key issue for cardiovascular health discussion.
Plaque goes through cycles of worsening and improving. As plaque heals, it becomes fibrous and calcified. Calcified plaque is safer than soft plaque by factors higher than 6x (Honda, 2004).
This fact, however, creates a paradox. If calcification signifies plaque healing and stabilization, then why are higher calcium scores indicative of higher risk?
That’s because there is evidence that higher coronary calcium scores represent higher plaque generation.
What does this mean?
A person with a higher score means his/her arteries have already undergone several cycles of inflammation (creating soft plaques) and calcification (converting soft plaques to calcified plaque). The presence of those calcified plaques is what is calculated as a calcium score.
Now, if inflammation is already arrested, then calcium score should be stable and not change. Some people can even reverse their calcium score, like in John’s case.
However, if inflammation still prevails, expect the calcium score to continue increasing.
Could a Patient with a Zero or Low Calcium Score Still Have Soft Plaque?
It’s possible. Calcium scoring does not detect new or soft plaque. It only detects calcified plaque.
Each year, I see patients who have deceptively low calcium scores but have soft plaque found in a CIMT (carotid intima-media thickness) exam.
Soft Plaque vs. Calcified Plaque: Which is More Dangerous?
According to the Honda study, calcified plaque is more stable (less dangerous) than soft plaque (Honda, 2004).
Soft plaque vs. calcified plaque – Appearance. The left shows “low IBS plaque,” which means soft or “hot” plaque, or in this study, “echolucent” plaque. The image on the right shows “high IBS plaque,” also referred to as calcified, hard, or “echogenic” plaque. (Echolucent plaques let ultrasonic waves pass through with no echo; thus, they appear to be transparent. Echogenic plaques reflect ultrasound waves; they appear as solid white mass.) Source: Honda O, Sugiyama S, Kugiyama K, Fukushima H, et al. Echolucent carotid plaques predict future coronary events in patients with coronary artery disease.
How did the researchers reach this conclusion?
The researchers followed subjects for an average of 14 months (up to 30 months) for cardiovascular events. As for the results, they found that:
- Out of 112 patients with soft, echolucent plaque, 29 patients had cardiovascular events (25.9%).
- Out of 103 patients with calcified, echogenic plaque, only 4 patients had events (3.9%).
Soft plaque vs. calcified plaque – Number of events. Source: Honda O, Sugiyama S, Kugiyama K, Fukushima H, et al. Echolucent carotid plaques predict future coronary events in patients with coronary artery disease.
Now we have a good idea of how people with calcified plaques would fare against people with soft plaques. Such things happened even though calcified plaques were slightly larger than soft plaques.
In other words, plaque size was less important to future cardiovascular events than the presence (or absence) of calcium in plaques.
Should We Worry About a High Calcium Score?
If you have a high calcium score, don’t fret… yet. We have to look at the larger picture.
After discussing soft and calcified plaques, we know now that calcified plaques are more preferred as they are more stable. And a higher calcium score denotes the presence of more calcified plaques.
Take these notes from my talk with Gerry, a patient of mine, whose story presents an exemplary case of calcium score reversal.
Calcium score measures calcium. It doesn’t measure soft plaque. I’ve had to talk to very successful patients multiple times when they experienced this phenomenon… They do some great work in terms of improving their situation, and instead of getting their expected decrease in calcium score, they get a big increase…
As you improve the stability of your plaque, when you begin to manage those, the plaques shrink just a little bit, but most of all, they begin as soft plaque. They also begin to develop a fibrous material. They go from a soupy, unstable consistency to a hybrid, stable consistency that has calcium in it. My perspective that you had the same thing happen to you that happened to so many successful patients.
…There’s a logical twist or irony with the calcium score. You put down more calcium as you begin to heal. It is a long-term reflection of risk, but short-term, it can be the opposite. That’s one of the major problems with a calcium score.
Remember: As long as we’re doing things to manage and stabilize our plaque, then we should be in a good situation, even if our calcium score is over 1,000.
Radiation Risk
Coronary calcium score uses CT, and therefore, X-ray. Thus, it is not entirely harmless as it exposes the patient to radiation.
There is some debate about this issue. Some say calcium scoring is dangerous because it has radiation. Others say that the amount of radiation is so small, it’s insignificant.
As often happens with debates, both sides are right. It’s just a question of context.
Let’s put the radiation risk in perspective.
One, the radiation dose from each of the 8 million nuclear stress tests done annually is over 10 times the radiation dose from a single calcium score.
Two, as more modern equipment becomes available, the radiation doses necessary to secure a quality image will likely shrink. Older equipment delivers up to 2,000 times the radiation dose of a single chest X-ray. For some newer machines, it’s close to 10 times only.
Three, the radiation risk is the reason coronary calcium scoring is not done on young, healthy subjects. Review committees for studies involving human subjects would never agree to radiate healthy people just to document calcium scores. This tilts the advantage to CIMT, which can provide measurements for healthy subjects of all ages as it uses ultrasound with no ionizing radiation.
Cancer Risk vs. Cardiovascular Risk
Four, calcium scoring is not harmless, but the risk of cancer from radiation exposure is minimal if you compare it to the cardiovascular risk in middle-aged individuals.
The lifetime cancer risk that can be incurred from the radiation of calcium scoring is about 1%. But that’s in a newborn who’s got a projected lifespan of over 70 years to develop cancer, not in a 50- or 60-year-old.
Moreover, people getting a calcium score usually would like to know if their risk of a heart attack or stroke over the next 10 years is close to 5% or 25%. And most would agree that the radiation risk is worth it in exchange for getting such a critical piece of information.
If the risk of heart attack and stroke with untreated plaque is 40 to 81% in just 10 years (as shown by the CAFES-CAVE study), then the additional risk of cancer from radiation appears to be acceptable (Belcaro, 2001).
How Much Radiation is Involved?
There has been some debate regarding how much radiation is routinely involved. Initially, the exposure was between 2 and 10 mSv (millisievert is the amount of radiation absorbed by the body).
However, a study nested within the MESA study found the radiation exposure to be closer to 1 mSv (Messenger, 2016). As you can see, the radiation exposure is improving each year.
Even the earlier, higher radiation risk estimates are not that high compared to the risk of heart attack and stroke that’s demonstrated by the CAFES-CAVE study.
Do I Recommend the Coronary Calcium Score?
The coronary calcium score is widely available, inexpensive, and reliable. So why not just screen plaque with calcium scoring?
If I didn’t have a better test available right now (which is the more reliable CIMT), that’s what I’d exactly do—I would screen patients with calcium scores. Moreover, when I have reason to suspect plaque, but it’s not showing on the CIMT, I think of calcium score.
Nowadays, I’m likely to start getting calcium scores more often. Here’s why.
In my current practice, most of my patients come from my YouTube channel. They see my discussions of CIMT, and they go on ordering their test from local CIMT providers.
However, I often get patients coming in with terrible CIMT results from their providers. These results rarely have arterial age or even IMT; they are usually just flow studies. And even if their CIMT providers did measure the plaque, they often lack the “mean max” (the average of the highest peaks or discreet plaques).
That’s why I’m now likely to recommend a calcium score first. It is so much easier and quicker to access providers of high-quality calcium scores.
Is the Calcium Score Becoming More Accepted?
Yes. The calcium score is more popular than CIMT to many in the preventive community.
I completely understand why. It’s even becoming accepted in the curative medical community, and that acceptance is moving more quickly than the acceptance of CIMT.
Why?
Again, calcium score is more widely available, and it doesn’t suffer from provider technique variations we often see in CIMT.
Why Don’t I Use More Calcium Score Tests?
Calcium score is a good test. But if there’s a wider access to high-quality CIMT providers, then I would go with CIMT.
Why?
CIMT with the providers I now have access to is a more superior test. For one, CIMT can detect soft plaques, something a calcium score can’t do.
Calcium score is also not very specific. In CIMT, you can get your arterial age in years. You saw mine with an arterial age of 74 years dropping continuously to 54. A calcium score is nowhere near that specific.
So, with calcium scores, I can’t give the patient much of an assessment regarding how bad their problem is. Plus, I can’t monitor their progress.
And I can do both—assessment and monitoring—with CIMT.
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References
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