Soft plaque is the fatty, non-calcified part of the buildup inside an artery wall. Calcified plaque is plaque in which calcium has been deposited, which makes it hard and easy to see on a CT scan. They are stages of the same disease, and most people with plaque have both.
Soft, fatty plaque is the type most closely tied to heart attacks, and very dense calcium tends to mark plaque that is more stable. But a high calcium score still means a lot of plaque overall, so neither type can be judged alone.
Key takeaways
- Soft and calcified plaque are not rival conditions; calcium is laid down in plaque as it ages.
- Studies using CT angiography link fatty, low-density plaque to future heart attacks more strongly than narrowing or calcium score.
- For the same amount of calcium, denser calcium has been associated with lower risk, but more calcium still means more risk.
- A calcium score sees only calcified plaque, so soft plaque in the heart arteries needs a contrast CT to be seen.
- Intensive cholesterol lowering changes plaque modestly; nobody can promise clean arteries.
Two stages of one process
Plaque begins when cholesterol-carrying particles get trapped in the artery wall and the immune system reacts. Over years this forms a fatty core covered by a fibrous cap. Later, calcium is deposited in older parts of the plaque.
So soft plaque is generally younger and calcified plaque is older, and one artery can hold both. Our guide to how arterial plaque builds up covers the biology step by step. This article looks at how the two types differ in risk and in what tests can show.
| Feature | Soft (non-calcified) plaque | Calcified plaque |
|---|---|---|
| What it is | A fatty core with immune cells under a fibrous cap | Older plaque with calcium deposits |
| Seen on a calcium score | No | Yes |
| Seen on a CT angiogram | Yes | Yes |
| Link to heart attacks | Fatty, low-density plaque was the strongest predictor in one large CT study | More calcium means more risk overall. Denser calcium means less risk for the same amount |
| With intensive statin treatment | Total plaque volume shrank slightly in pooled trials | Calcification increased |
Which one is riskier?
Most heart attacks start when a plaque tears or wears away at its surface and a clot forms on it. The plaques that do this tend to have a large fatty core and a thin cap. That is the reasoning behind calling soft plaque less stable.
Imaging studies support it. Researchers measured plaque on CT angiograms from 1,769 patients with stable chest pain and followed them for a median of 4.7 years. The amount of low-density, non-calcified plaque was the strongest predictor of a later heart attack, ahead of a clinical risk score, the calcium score and the degree of narrowing.1
Risky plaque also does not have to be causing a blockage. In a study of people who went on to have an acute coronary event, 81% of the plaques with high-risk features narrowed the artery by less than half.2
Is calcium protective? Not quite
It is tempting to conclude that calcified plaque is the safe kind. The evidence says something narrower.
In 3,398 MESA participants who had calcium on a scan, a larger volume of calcium was linked to more cardiovascular events, while denser calcium was linked to fewer events at any given volume.3 A separate CT study found that people who later had an acute coronary event had a similar total volume of calcified plaque to those who did not, but less of the very densest calcium.4
So density looks like a marker of stability. Volume is a marker of how much disease there is. The standard calcium score rises with both, and in practice a high score is still a warning, because people with a lot of calcium usually have plenty of soft plaque too. In the chest pain study above, the amount of low-density plaque tracked closely with the calcium score.
What each test can and cannot see
Calcium score. A coronary calcium scan detects calcified plaque only. A score of zero lowers the odds of significant plaque but does not rule out soft plaque.
CT angiogram. A CT with contrast dye shows both types and how much they narrow the artery. It is a diagnostic test, used mainly for people with symptoms. We compare the two scans in calcium score vs. CT angiogram.
Carotid ultrasound. An ultrasound of the neck arteries, including CIMT, can show plaque there. It is an indirect clue about the heart. US guidance from 2013 does not recommend routine CIMT measurement for predicting a first cardiovascular event.5
Blood tests. ApoB, Lp(a) and hs-CRP do not image plaque of either type. They measure the forces that build it.
What treatment does to each type
Lowering cholesterol particles does not simply dissolve plaque. In a pooled analysis of eight trials that used ultrasound inside the coronary arteries, plaque volume fell slightly with high-intensity statin therapy and grew with low-intensity or no statin therapy. Calcium increased in every group, and more so with statins.6
The authors' reading was that statins may stabilize plaque partly by calcifying it. One practical consequence: a calcium score can rise on treatment without meaning the treatment has failed. Our article for people already on a statin explains how to read a score in that setting.
Keep expectations honest. The changes in plaque volume seen in trials are small, and no test or treatment can promise to clear your arteries. Do not start, stop or change a medication without your prescriber.
Your next step: know what your tests can show
At our clinic, the Enhanced Assessment ($999) includes a coronary calcium score, which measures calcified plaque, and a CIMT ultrasound of the neck arteries. Neither Cardio Res-Q assessment includes a CT angiogram, so soft plaque in the heart arteries is not imaged directly. If that question matters in your case, it is one for a cardiologist.
Both the Enhanced and the Comprehensive Assessment ($775) measure ApoB, Lp(a) and hs-CRP, which describe what is driving plaque of either type. To compare the two options, read Comprehensive vs. Enhanced Assessment or visit the Cardio Res-Q program page.
Are You a Candidate for Cardio Res-Q?
Three quick questions about the risk factors we screen for. Your answers stay between you and the clinic.
Frequently asked questions
Does a calcium score of zero mean I have no soft plaque?
No. A calcium scan cannot see plaque that has not calcified. A zero makes significant plaque less likely and is reassuring for most people without symptoms, but it is not proof of clean arteries, and it does not explain symptoms.
Does soft plaque turn into calcified plaque?
Often, over years. Calcium is deposited as plaque ages, and trial data suggest statin treatment speeds that calcification. This is one reason calcium scores tend to rise over time, even in people whose risk is being well managed.
Can soft plaque go away?
Trials of intensive cholesterol lowering have shown small reductions in plaque volume, not disappearance. The realistic aims are slower growth, more stable plaque and lower risk. Be cautious of anyone who promises more than that.
Is a high calcium score good news, since calcified plaque is more stable?
No. A high score means a large amount of plaque, and people with more calcium have more cardiovascular events. Density is a finer point within the score. It does not turn a high score into a low-risk result.
Related reading
This article is for general education and is not medical advice. Decisions about testing and medication should be made with your clinician. If you have chest pain or other symptoms of a heart attack, call 911.
