Coronary Calcium Isn't the Only Answer: Why Carotid Artery Ultrasound Deserves a Second Look

Table of Contents

• Key Points
• Why Accurate Heart Risk Assessment Matters
• The MESA Study: A Major Research Effort
• Understanding the Tests: Coronary Calcium, IMT, ABI, and Carotid Plaque
• Key Findings: What the MESA Study Showed
• The Hidden Cost of Coronary Calcium Scans: Radiation Exposure
• Why Carotid Plaque Ultrasound Deserves More Attention
• What Other Research Says About Carotid Plaque Measurement
• Clinical Implications: What This Means for Patients and Doctors
• Limitations of This Correspondence
• Recommendations for Patients
• Frequently Asked Questions
• Source Information

Key Points

• Carotid plaque ultrasound is cheaper and radiation-free compared to coronary calcium CT scans.
• Coronary calcium scoring predicts risk well, but carotid plaque burden may add comparable value.
• The MESA study did not directly compare coronary calcium with carotid plaque burden.
• The Tromsø Study found carotid plaque area strongly predicts first-ever ischemic stroke.
• Direct imaging of plaque in your arteries can refine risk beyond traditional risk calculators.

Why Accurate Heart Risk Assessment Matters

Every year, millions of people worldwide experience heart attacks and strokes, often with little warning. For decades, doctors have relied on risk calculators that combine factors like age, blood pressure, cholesterol levels, smoking status, and diabetes to estimate a person's chance of having a cardiovascular event. These calculations—often called "panels of risk factors"—are useful, but they have an important limitation: they estimate risk based on population averages rather than directly looking at whether a person actually has plaque buildup (atherosclerosis) in their arteries.

Atherosclerosis is the process by which fatty deposits, cholesterol, and other substances build up inside artery walls, forming plaque. Over time, this plaque can narrow arteries, restrict blood flow, and—most dangerously—rupture, causing blood clots that lead to heart attacks or strokes. The disease develops silently over decades, which is why detecting it early is so valuable.

Dr. Spence makes a key point: directly measuring the burden of atherosclerosis is much better for predicting risk than calculating it from risk factor panels. This aligns with a growing shift in cardiovascular medicine toward "imaging-based" risk assessment.

The MESA Study: A Major Research Effort

The article at the center of this debate comes from the Multi-Ethnic Study of Atherosclerosis (MESA), one of the most influential research projects in cardiovascular medicine. MESA is a large, long-term study that enrolled participants from multiple ethnic backgrounds to investigate how atherosclerosis develops and how it predicts future cardiovascular events.

In 2019, Zhao and colleagues published a paper from MESA examining multisite atherosclerosis—that is, plaque buildup in different parts of the body—in people with metabolic syndrome and diabetes. The study compared how well different screening tests predicted cardiovascular events, including:

• Coronary calcium scoring – a CT scan (computed tomography) that measures calcified plaque in the coronary arteries (the arteries that supply blood to the heart muscle)
• Carotid intima-media thickness (IMT) – an ultrasound measurement of the thickness of the inner two layers of the carotid artery wall in the neck
• Ankle-brachial index (ABI) – a simple blood pressure comparison between the ankle and the arm that can indicate blockages in leg arteries

The findings, as reported in the correspondence, showed that coronary calcium scores predicted most of the risk of cardiovascular events, with little additional contribution from carotid IMT or ABI. In other words, once you know a patient's coronary calcium score, measuring IMT or ABI didn't add much predictive value.

Understanding the Tests: Coronary Calcium, IMT, ABI, and Carotid Plaque

To understand the debate, it helps to know the differences between the tests being compared. They each look at atherosclerosis in different ways, at different parts of the body, and with different technologies.

Coronary calcium scoring uses a computed tomography (CT) scan of the chest to detect and quantify calcium deposits in the coronary arteries. Because calcium accumulates in atherosclerotic plaque over time, the calcium score (often called the Agatston score) serves as a proxy for total plaque burden in the heart's arteries. Higher scores mean more plaque and higher risk. The scan is quick, painless, and requires no contrast dye, but it does involve exposure to ionizing radiation.

Carotid intima-media thickness (IMT) uses ultrasound to measure the thickness of the two innermost layers of the carotid artery wall—the intima and the media. Increased thickness indicates early arterial wall changes consistent with atherosclerosis. It's a measure of the artery wall itself, not specifically of the plaque protruding into the artery.

Ankle-brachial index (ABI) is the simplest test: it divides the systolic blood pressure at the ankle by the systolic blood pressure at the arm. A low ratio (below about 0.90) suggests there are blockages in the arteries of the legs, which is associated with widespread atherosclerosis elsewhere in the body.

Carotid plaque burden—the measurement Dr. Spence advocates—uses ultrasound to directly visualize and measure plaque in the carotid arteries. Unlike IMT, which measures the wall thickness, plaque burden quantifies the actual plaque area or volume. This can be done with standard two-dimensional (2D) ultrasound, which measures plaque area, or with three-dimensional (3D) ultrasound, which measures plaque volume (a reflection of the total amount of disease).

Key Findings: What the MESA Study Showed

The MESA paper by Zhao et al. reported that coronary calcium scores predicted most of the risk of cardiovascular events, with little contribution from carotid IMT and ankle-brachial index. This means that, statistically, the coronary calcium score was the dominant predictor among the tests evaluated.

In response, Dr. Paolo Raggi wrote an accompanying editorial in the same journal. His now-famous statement was: "Coronary calcium is all we need for risk assessment, yet we do not use it often enough." Raggi's editorial argued that coronary calcium scoring should be used more widely because it provides such strong risk prediction.

Dr. Spence agrees with part of this argument. He states clearly that "assessing burden of atherosclerosis is much better for predicting risk than calculations from panels of risk factors." He also agrees that coronary calcium is "much better than IMT and ankle-brachial index" for this purpose. So far, the authors are in agreement.

The disagreement lies in what was left out. Dr. Spence notes that the MESA analysis and the accompanying editorial omitted mention of ultrasound measurement of carotid plaque burden—a test that he argues is at least as good as coronary calcium, while being cheaper and safer.

The Hidden Cost of Coronary Calcium Scans: Radiation Exposure

One of Dr. Spence's most practical concerns is radiation exposure. A single coronary calcium CT scan involves a relatively small dose of ionizing radiation—comparable to a few mammograms or chest X-rays. For most healthy people scanned once, the risk is very small.

However, Dr. Spence makes an important point: patients with coronary artery disease tend to have repeated exposure to radiation. These patients often undergo:

• Coronary angiograms (invasive dye studies of the heart's arteries)
• Percutaneous revascularization procedures (such as angioplasty and stent placement)
• Follow-up CT scans

Each of these procedures adds to a patient's lifetime radiation dose. The medical community understands that the risk of radiation is cumulative—meaning that the effects of many small exposures add up over time. While each individual scan or procedure may pose negligible risk on its own, the combined exposure across a patient's lifetime can increase the risk of cancer.

Carotid ultrasound, by contrast, uses no ionizing radiation at all. It relies on sound waves, which are harmless and have no known cumulative risk. This makes ultrasound an attractive option for patients who need repeated monitoring of their atherosclerosis over time.

Why Carotid Plaque Ultrasound Deserves More Attention

Dr. Spence's central argument is that ultrasound measurement of carotid plaque burden offers three key advantages over coronary calcium scoring:

1. Much lower cost. Carotid ultrasound is significantly cheaper than CT-based coronary calcium scoring. This matters both for healthcare systems and for individual patients paying out of pocket. Lower cost also makes it more feasible to repeat the test over time to track disease progression or regression.
2. No radiation exposure. As noted above, this eliminates a cumulative risk, especially important for patients who will need repeated imaging over a lifetime.
3. Comparable (or better) predictive ability. While the MESA analysis didn't directly compare coronary calcium with carotid plaque burden, other large studies—described below—have shown that carotid plaque burden is a strong predictor of cardiovascular events.

Dr. Spence is careful not to dismiss coronary calcium scoring entirely. He acknowledges it is a valuable tool—in fact, better than IMT and ABI. His point is narrower but important: the conversation about risk imaging should include carotid plaque ultrasound as a first-line option, especially in settings where cost and radiation are concerns. As he puts it, "coronary calcium is not all we need."

What Other Research Says About Carotid Plaque Measurement

Dr. Spence supports his argument by referencing a body of research on carotid plaque measurement that has accumulated over nearly two decades. One particularly notable study is the Tromsø Study, a Norwegian population-based study that followed 6,584 men and women for 10 years. Published in the journal Stroke in 2011 by Mathiesen and colleagues, it examined the ability of carotid plaque area and intima-media thickness to predict first-ever ischemic stroke (stroke caused by a blocked blood vessel). The study found that carotid plaque area was a strong predictor of stroke risk, supporting the clinical value of measuring plaque directly.

Other important research cited in the correspondence includes:

• Spence et al. (2002) – published in Stroke, demonstrated that carotid plaque area is a useful tool for targeting and evaluating vascular preventive therapy. This study laid groundwork for using plaque measurements in everyday clinical practice.
• Sillesen et al. (2012) – published in JACC: Cardiovascular Imaging, compared carotid plaque burden with other tests for subclinical arterial disease in the High Risk Plaque BioImage Study, finding that carotid plaque burden performed well as a measure of subclinical atherosclerosis (disease present but not yet causing symptoms).
• Baber et al. (2015) – also from the BioImage Study, published in the Journal of the American College of Cardiology, examined the prevalence, impact, and predictive value of detecting subclinical coronary and carotid atherosclerosis in asymptomatic adults, adding further evidence that both measurements can identify high-risk individuals before events occur.
• Ainsworth et al. (2005) – published in Stroke, showed that 3D ultrasound can reliably measure changes in carotid plaque volume, making it a valuable tool for rapidly evaluating new therapies.
• Spence et al. (2010) – published in the Archives of Neurology, found that intensive medical therapy reduced microemboli (tiny particles traveling in the bloodstream) and lowered cardiovascular risk in patients with asymptomatic carotid stenosis (narrowing of the carotid artery without prior symptoms).
• Spence (2014, 2017) – in Atherosclerosis and the Journal of the American College of Cardiology, discussed the time course of atherosclerosis regression and progress toward automated 3D measurement of plaque volume, suggesting that ultrasound technology is advancing to make this measurement even more practical.

Together, these studies paint a clear picture: measuring carotid plaque with ultrasound is not a fringe idea. It has been validated in large populations, across multiple international research groups, and in both 2D and 3D forms.

Clinical Implications: What This Means for Patients and Doctors

For patients, this correspondence reinforces an important shift in thinking: your risk of heart attack and stroke is better estimated by looking at your actual arteries than by plugging your numbers into a risk calculator.

If you have been told you are at "intermediate risk" based on traditional risk factors—like borderline cholesterol, slightly elevated blood pressure, or family history—your doctor may recommend additional testing. The question is which test. This article suggests that patients have options, and that the choice should weigh:

• Cost of the test
• Whether you may need repeated imaging over time
• Cumulative radiation exposure (especially if you've already had angiograms, stents, or other radiation-based procedures)
• What your doctor is looking for (e.g., plaque in the heart arteries vs. plaque in the neck arteries)

For doctors, the message is about shared decision-making and comprehensive assessment. Coronary calcium scoring is a powerful tool—but it's not the only one. Carotid plaque ultrasound offers comparable information about systemic atherosclerosis burden at a fraction of the cost, with no radiation, and it can be repeated safely to track whether treatment is working.

The correspondence also has implications for health policy. If carotid plaque ultrasound is as effective as coronary calcium scoring but cheaper and safer, health systems might consider covering it as a first-line screening option for patients at intermediate cardiovascular risk.

Limitations of This Correspondence

It's important to point out that this article is a correspondence letter, not a new clinical trial. It presents an opinion and a critique, supported by reference to other published research. As such, it has limitations:

• It does not present new data comparing coronary calcium scoring and carotid plaque burden head-to-head in a single study.
• The author's conclusions rely on his interpretation of existing studies, and other experts (like Dr. Raggi) may interpret the same evidence differently.
• The original MESA analysis it critiques did not include carotid plaque burden as a measured variable, so we cannot know from that specific study how it would have compared.
• Coronary calcium scoring may be better than carotid plaque ultrasound specifically for predicting heart events, while carotid measures may be better for predicting stroke. The "best" test may depend on the outcome of interest.

Nevertheless, the correspondence is valuable because it highlights a real gap in the conversation and reminds both doctors and patients that evidence-based options exist beyond the most frequently discussed tests.

Recommendations for Patients

Based on the evidence discussed in this article, here are some practical steps to consider:

1. Talk to your doctor about imaging-based risk assessment. If you're at intermediate risk (10-20% ten-year risk) based on traditional risk factors, ask whether an imaging test could help refine that estimate.
2. Ask about carotid ultrasound. Specifically inquire whether carotid plaque burden measurement (not just IMT) is available and appropriate for you. If you're concerned about radiation or cost, ultrasound may be a particularly good option.
3. Know your radiation history. If you've already had multiple CT scans, angiograms, or stent procedures, mention this to your doctor. Your cumulative radiation exposure should factor into decisions about additional radiation-based testing.
4. Don't ignore plaque, even if your cholesterol looks "OK." Many people with heart attacks have normal cholesterol levels. Direct imaging of atherosclerosis can reveal risk that blood tests miss.
5. Use imaging results to motivate prevention. Research shows that when patients see evidence of plaque in their own arteries, they're more likely to adhere to medications and lifestyle changes. A carotid ultrasound result can be a powerful wake-up call—and, conversely, a clear scan can provide reassurance.
6. Remember that no single test is perfect. The best approach may combine multiple assessments. If your doctor recommends coronary calcium scoring, that's reasonable—but it's also reasonable to ask, "Is there a radiation-free alternative?"

Frequently Asked Questions

What is the difference between coronary calcium scoring and carotid plaque ultrasound?

Coronary calcium scoring uses a CT scan to measure calcified plaque in the heart's arteries. Carotid plaque ultrasound uses sound waves to directly measure plaque in the neck arteries. Both estimate your overall plaque burden, but ultrasound is cheaper, uses no radiation, and can be repeated safely.

Why does Dr. Spence say carotid plaque ultrasound should be considered?

Dr. Spence argues that carotid plaque ultrasound is less expensive, avoids radiation exposure, and has comparable predictive ability to coronary calcium scoring. He believes the conversation about risk imaging should include it as a first-line option, especially when patients may need repeated imaging over time.

Does carotid plaque ultrasound use radiation?

No. Carotid plaque ultrasound uses harmless sound waves and has no known cumulative risk. Coronary calcium CT scans expose you to ionizing radiation, and repeated scans add up over a lifetime, potentially increasing cancer risk. This makes ultrasound safer for patients who need ongoing monitoring.

What did the MESA study show about coronary calcium scoring?

In the MESA study, coronary calcium scores predicted most of the risk of cardiovascular events, with little additional contribution from carotid IMT or ankle-brachial index. However, the study did not directly compare coronary calcium with carotid plaque burden, which Dr. Spence says was a missed point.

What is carotid intima-media thickness (IMT) and how is it different from carotid plaque burden?

Carotid IMT measures the thickness of the inner two layers of the carotid artery wall, indicating early changes. Carotid plaque burden directly visualizes and measures the actual plaque area or volume. Plaque burden is a more direct measure of disease, and Dr. Spence argues it is better than IMT for risk prediction.

Who might benefit from asking about carotid plaque ultrasound?

People at intermediate cardiovascular risk—such as those with borderline cholesterol, slightly high blood pressure, or family history—might benefit. Also, patients concerned about radiation or cost, or those who have already had multiple CT scans or angiograms, may want to ask their doctor if carotid plaque ultrasound is appropriate.

What did the Tromsø Study find about carotid plaque area and stroke risk?

The Tromsø Study followed 6,584 men and women for 10 years. It found that carotid plaque area was a strong predictor of first-ever ischemic stroke, supporting the value of measuring plaque directly. This study adds evidence that carotid plaque ultrasound is a useful tool for stroke risk assessment.

Source Information

Original article: Spence JD. "Coronary calcium is not all we need: Carotid plaque burden measured by ultrasound is better." Atherosclerosis, Volume 287, Pages 179-180.

Author: J. David Spence, MD, FRCPC, FAHA — a leading researcher in stroke prevention and atherosclerosis imaging at Western University, London, Ontario, Canada.

Publication history: Received March 24, 2019; revised March 28, 2019; accepted April 10, 2019; published online April 17, 2019. Copyright © 2019 Elsevier B.V. All rights reserved.

DOI: 10.1016/j.atherosclerosis.2019.04.214

References discussed in this article:

• Zhao Y, Evans MA, Allison MA, et al. Multisite atherosclerosis in subjects with metabolic syndrome and diabetes and relation to cardiovascular events: the Multi-Ethnic Study of Atherosclerosis. Atherosclerosis 2019;282:202-209.
• Raggi P. Coronary calcium is all we need for risk assessment, yet we do not use it often enough. Atherosclerosis 2019;282:167-168.
• Spence JD, Eliasziw M, DiCicco M, et al. Carotid plaque area: a tool for targeting and evaluating vascular preventive therapy. Stroke 2002;33:2916-2922.
• Mathiesen EB, Johnsen SH, Wilsgaard T, et al. Carotid plaque area and intima-media thickness in prediction of first-ever ischemic stroke: a 10-year follow-up of 6,584 men and women: the Tromsø Study. Stroke 2011;42:972-978.
• Sillesen H, Muntendam P, Adourian A, et al. Carotid plaque burden as a measure of subclinical atherosclerosis: comparison with other tests for subclinical arterial disease in the High Risk Plaque BioImage study. JACC Cardiovasc Imaging 2012;5:681-689.
• Baber U, Mehran R, Sartori S, et al. Prevalence, impact, and predictive value of detecting subclinical coronary and carotid atherosclerosis in asymptomatic adults: the BioImage study. J Am Coll Cardiol 2015;65:1065-1074.
• Ainsworth CD, Blake CC, Tamayo A, et al. 3D ultrasound measurement of change in carotid plaque volume: a tool for rapid evaluation of new therapies. Stroke 2005;36:1904-1909.
• Spence JD, Coates V, Li H, et al. Effects of intensive medical therapy on microemboli and cardiovascular risk in asymptomatic carotid stenosis. Arch Neurol 2010;67:180-186.
• Spence JD. Time course of atherosclerosis regression. Atherosclerosis 2014;235:347-348.
• Spence JD. Approaching automated 3-dimensional measurement of atherosclerotic plaque volume. J Am Coll Cardiol 2017;70:314-317.

This patient-friendly article is based on peer-reviewed research published in Atherosclerosis, one of the leading international journals in the field of vascular medicine. All statistics and study findings have been preserved from the original source. This content is provided for educational purposes and is not a substitute for professional medical advice. Always consult your healthcare provider about your individual risk and testing options.