February is American Heart Month, an important reminder that cardiovascular disease (CVD) remains the leading cause of death in the United States. Despite advances in lipid testing, risk calculators, and preventive therapies, many individuals still experience cardiovascular events without prior warning. One major reason is that atherosclerosis often develops silently for decades before symptoms appear.
In Functional Medicine, we aim to identify risk earlier and more precisely, not just by estimating probability based on population data, but by understanding what is actually happening inside an individual patient’s arteries. Imaging-based cardiovascular screening allows us to move beyond surrogate risk markers and directly assess subclinical atherosclerosis, helping personalize prevention strategies and avoid both under- and overtreatment.
This article reviews three commonly discussed imaging options for cardiovascular risk assessment, carotid ultrasound (cIMT and plaque), coronary artery calcium scoring (CAC), and coronary CT angiography (CCTA), and explores how artificial intelligence, including tools such as Cleerly, is reshaping how we interpret and apply these tests in clinical practice.
Why Imaging Matters in Cardiovascular Prevention
Traditional risk calculators estimate 10-year cardiovascular risk using age, cholesterol, blood pressure, diabetes, and smoking status. While useful, they often fall short for individuals with risk enhancers frequently seen in Functional Medicine clinics, including insulin resistance, inflammatory conditions, early menopause, autoimmune disease, elevated lipoprotein(a), ApoB discordance, sleep apnea, or strong family history of premature cardiovascular disease.
Imaging answers a fundamentally different question: Is atherosclerosis already present, and if so, how much? This distinction is critical, because treatment decisions become clearer when disease burden is visible rather than inferred.
Carotid Ultrasound (cIMT and Plaque Assessment)
Carotid ultrasound is a broad imaging modality used to evaluate the carotid arteries. In conventional clinical practice, it is most commonly performed to assess carotid stenosis, flow characteristics, and the presence of plaque, particularly in the context of stroke or transient ischemic attack risk. It’s important to note that carotid ultrasound reports stenosis using velocity-based criteria that correspond to specific percentage thresholds, with ≥50% stenosis being the first clinically significant category reported as “blockage” or hemodynamically significant disease, which feels like a significant limitation to me.
Within cardiovascular prevention, a more specific application is carotid intima-media thickness (cIMT), a standardized measurement of the thickness of the arterial wall layers intended to reflect vascular aging and subclinical atherosclerosis.
It is important to distinguish between these two uses. Not all carotid ultrasounds include a validated cIMT protocol, and not all cIMT measurements are equivalent. Predictive value depends heavily on standardized acquisition, segment selection, and whether plaque is identified and reported.
What the evidence shows
Large prospective cohort studies support cIMT as an independent predictor of cardiovascular events. Early landmark studies, including the Cardiovascular Health Study and ARIC, demonstrated a graded relationship between increasing cIMT and risk of myocardial infarction and stroke. Later data from the Framingham Offspring cohort showed that internal carotid IMT and plaque presence, rather than common carotid IMT alone, improved cardiovascular risk classification beyond traditional risk factors.
cIMT also appears to have particular relevance for cerebrovascular risk, with multiple studies and meta-analyses demonstrating associations between increased cIMT and ischemic stroke. This distinction helps explain why carotid-based measures may still be clinically informative in selected patients where stroke risk context is central.
At the same time, important limitations have emerged. Large pooled analyses, including the PROG-IMT collaboration, confirm that while baseline cIMT predicts events, changes in cIMT over time do not reliably predict future cardiovascular outcomes. This limits the value of serial cIMT testing as an outcomes-validated progression marker.
Strengths
- No radiation or contrast
- Widely available and relatively low cost
- Can identify carotid plaque, which is clinically meaningful for vascular aging and stroke risk context
Limitations
- Significant operator and protocol variability
- cIMT provides only modest incremental risk prediction beyond traditional risk factors
- Change in cIMT over time does not reliably correlate with event reduction
- U.S. guidelines recommend against routine cIMT measurement for first-event cardiovascular risk assessment due to limited clinical utility
Clinical context
While carotid plaque and cIMT clearly reflect systemic atherosclerotic burden, the carotid arteries are not a direct surrogate for the coronary arteries. Head-to-head studies consistently show that coronary artery calcium scoring outperforms cIMT for predicting coronary events, which is why CAC has become the preferred imaging tool for refining coronary risk in asymptomatic individuals.
For these reasons, carotid ultrasound CIMT is best viewed as a selective, complementary tool, rather than a primary screening modality for coronary risk stratification. In Functional Medicine practice, it may add value in specific contexts, particularly when stroke risk, radiation avoidance, or broader vascular aging assessment is part of the clinical conversation, but it is rarely sufficient on its own to guide coronary prevention decisions.
Coronary Artery Calcium (CAC) Scoring
Coronary artery calcium (CAC) scoring uses a non-contrast, ECG-gated CT scan to quantify calcified atherosclerotic plaque within the coronary arteries, reported as an Agatston score. Unlike risk calculators, CAC directly measures established coronary atherosclerosis rather than estimating risk based on surrogate factors.
Why CAC has become the cornerstone of imaging-based risk assessment
Among available noninvasive imaging tools, CAC has the most consistent and reproducible evidence base for predicting future coronary events in asymptomatic individuals. Large prospective cohort studies and multiple meta-analyses demonstrate that CAC provides substantial incremental prognostic value beyond traditional risk factors, with meaningful improvements in discrimination and risk reclassification, particularly in intermediate-risk populations.
CAC consistently outperforms carotid IMT and carotid plaque measures for predicting coronary heart disease outcomes. This superiority underlies its endorsement in the 2018 ACC/AHA cholesterol guidelines as the preferred imaging tool to refine risk estimates when treatment decisions, particularly statin initiation or intensity, remain uncertain.
From a practical standpoint, CAC is fast, widely available, requires no contrast, and is associated with relatively low radiation exposure with modern scanners, making it feasible for broad preventive use.
Clinical interpretation of CAC scores
- CAC = 0 identifies individuals at very low short-term risk for coronary events. In appropriately selected patients, this finding can support deferral of statin therapy and avoid unnecessary pharmacologic escalation, while still reinforcing aggressive lifestyle, metabolic, and inflammatory risk factor management. Importantly, CAC = 0 reflects low near-term risk rather than lifetime risk.
- CAC 1–99 indicates early coronary atherosclerosis and generally supports preventive therapy, particularly in patients over age 55 or those with additional risk enhancers such as family history, insulin resistance, or elevated ApoB or lipoprotein(a).
- CAC ≥100 or a score above the 75th percentile for age and sex reflects a higher atherosclerotic burden and strongly supports intensive risk-reduction strategies, including lipid-lowering therapy, blood pressure optimization, and aggressive management of cardiometabolic drivers.
Important limitations and clinical caveats
Despite its strengths, CAC has meaningful limitations that must be clearly understood to avoid misinterpretation or overreliance.
First, CAC detects only calcified plaque. It does not visualize non-calcified or mixed plaque, which may be more prevalent in younger individuals, women, and patients with early or metabolically driven atherosclerosis. As a result, a CAC score of zero does not exclude the presence of non-calcified coronary plaque, nor does it eliminate long-term cardiovascular risk.
Second, CAC does not assess stenosis severity, plaque vulnerability, or coronary anatomy. It is a risk stratification tool, not a diagnostic angiogram. A high CAC score reflects plaque burden, not necessarily flow-limiting disease, and a low CAC score does not guarantee absence of functionally significant lesions.
Third, CAC is a static snapshot of calcified plaque burden. While higher scores correlate strongly with future event risk, CAC progression over time has not been definitively shown to serve as an outcomes-validated surrogate endpoint for treatment success. Serial CAC testing should therefore be approached cautiously and within a clear clinical rationale.
Fourth, while CAC improves risk prediction, randomized trials have not yet demonstrated that CAC-guided screening in asymptomatic populations reduces hard cardiovascular outcomes compared with traditional risk assessment alone. Observational data strongly support its prognostic value, but outcomes depend on how clinicians and patients act on the results.
Finally, CAC may be less informative in certain high-risk populations, including individuals with diabetes, chronic kidney disease, or strong genetic risk, where treatment decisions may already favor aggressive prevention regardless of imaging findings.
Clinical framing in preventive care
When used appropriately, CAC serves as a powerful decision-refining tool, helping clinicians calibrate prevention intensity rather than replace clinical judgment. Its greatest value lies in clarifying uncertainty, identifying patients who warrant earlier intervention, and avoiding overtreatment in those with truly low near-term risk.
In Functional Medicine, CAC is best interpreted alongside metabolic health, inflammatory burden, genetic risk, lifestyle factors, and patient preferences, recognizing both what the test reveals and what it cannot.
Coronary CT angiography (CCTA) uses contrast-enhanced, ECG-gated CT imaging to directly visualize the coronary arteries, allowing assessment of the vessel lumen and arterial wall. Unlike CAC scoring, which quantifies calcified plaque burden only, CCTA provides a more comprehensive evaluation of coronary atherosclerosis by identifying both calcified and non-calcified plaque, assessing plaque distribution across the coronary tree, and evaluating the degree of luminal narrowing.
Coronary CT Angiography (CCTA)
What CCTA adds beyond CAC
CCTA enables detection of non-calcified and mixed plaque, which is particularly relevant in younger individuals, women, and patients with metabolically driven or genetically mediated risk where plaque may not yet be calcified. It also allows for assessment of stenosis severity, offering insight into whether plaque is associated with potentially flow-limiting lesions.
CCTA has also been used to identify higher-risk plaque features, such as low-attenuation plaque or positive remodeling, which may be associated with increased event risk.
Evidence for risk prediction
Population-based studies support the incremental prognostic value of CCTA. In the Swedish SCAPIS cohort, adding CCTA-derived plaque data to traditional risk factors and CAC modestly but significantly improved discrimination and risk reclassification for future coronary events. These findings suggest that plaque characterization, not just plaque quantity, contributes meaningfully to risk assessment in selected populations.
However, it is important to distinguish risk prediction from outcomes benefit. While CCTA clearly improves anatomical and phenotypic understanding of coronary disease, evidence that CCTA-based screening in asymptomatic individuals reduces cardiovascular events remains limited.
Tradeoffs and limitations
CCTA involves several important considerations that limit its role as a first-line screening test.
Radiation exposure is higher than with CAC scoring, though it varies significantly based on scanner technology, acquisition protocols, and patient characteristics. CCTA also requires iodinated contrast, which introduces potential risks in patients with contrast allergy, chronic kidney disease, or reduced renal reserve.
Because CCTA visualizes the entire thorax, it carries a higher likelihood of incidental findings, such as pulmonary nodules or mediastinal abnormalities, which may necessitate additional imaging or follow-up. While sometimes clinically useful, these findings can also lead to patient anxiety and downstream testing without clear benefit.
CCTA results often require more nuanced interpretation and can trigger complex downstream care pathways, including functional testing or invasive angiography, particularly when moderate lesions are identified. Without a clear pre-test clinical plan, this can contribute to overtesting rather than improved outcomes.
Clinical role in preventive care
For these reasons, CCTA is generally not a first-line screening test for asymptomatic individuals but should be decided on a case by case basis. Its greatest value lies in selective use, such as when CAC results do not fully explain clinical concern, when non-calcified plaque is suspected despite low or zero CAC, or when more detailed plaque characterization is needed to guide shared decision-making.
In Functional Medicine practice, CCTA can serve as a problem-solving and phenotyping tool, rather than a broad screening modality, particularly when integrated with advanced lipid testing, metabolic assessment, and individualized risk discussions.
When used thoughtfully, CCTA deepens understanding of coronary disease biology, but its benefits depend heavily on appropriate patient selection, careful interpretation, and a clear plan for how results will influence care.
The Role of Artificial Intelligence in Coronary Imaging
Traditional CCTA interpretation has focused on visual estimation of stenosis and qualitative plaque descriptions. AI-based tools are changing this paradigm by enabling automated, quantitative plaque analysis.
Platforms such as Cleerly apply machine learning to coronary CT angiography data to measure:
- Total plaque volume
- Percent atheroma volume (PAV)
- Non-calcified plaque burden
- Detailed plaque characteristics across the coronary tree
In clinical studies, AI-derived plaque metrics have demonstrated prognostic value comparable to or exceeding CAC for predicting adverse cardiovascular outcomes. These tools shift imaging from a binary or categorical assessment to a continuous, trackable disease burden model.
Why this matters clinically
- Enables more precise risk stratification in selected patients
- Supports longitudinal monitoring of plaque burden
- Enhances patient understanding and engagement by visualizing disease in detail
AI does not replace clinical judgment. Thresholds for intervention based on AI plaque metrics are still evolving, and results must be interpreted within the broader clinical context.
What the Evidence Still Does Not Show
Despite strong prognostic data, randomized controlled trials demonstrating that imaging-based screening in asymptomatic individuals reduces cardiovascular events or mortality are limited. Existing trials show mixed effects on risk factor modification and adherence, and long-term outcome data are still emerging.
Notably, CCTA-guided management has demonstrated reduced myocardial infarction rates in symptomatic populations with stable chest pain, but this evidence cannot be directly extrapolated to asymptomatic screening.
Ongoing trials such as DANCAVAS, ROBINSCA, SCOT-HEART 2, and DANE-HEART are expected to provide critical data on whether imaging-based prevention improves hard outcomes and cost-effectiveness compared with traditional risk assessment alone.
Bringing This Into Functional Medicine Practice
Imaging is not a replacement for lifestyle medicine, metabolic optimization, or root-cause care. Instead, it functions as a decision-refining tool that helps answer three core questions:
- Is atherosclerosis present?
- How advanced is it?
- How aggressively should prevention be pursued right now?
When used thoughtfully, imaging can prevent unnecessary treatment in truly low-risk individuals and support earlier, more intensive intervention in those with silent disease.
