At Princeton Longevity Center, we are increasingly interested in a fundamental question in preventive cardiology: Can we identify specific areas of plaque in your arteries disease that may be more biologically active before it causes a heart attack?
That is becoming possible with advances in coronary CT angiography and artificial intelligence-assisted image analysis. Now, a Princeton Longevity cardiac CT doesn’t just tell you whether you have plaque in your coronary arteries. It can also gives your physician information about whether the environment around that plaque shows signs of inflammation that may indicate a higher risk plaque.
This promising new tool is called the perivascular fat attenuation index, or FAI. Using information already contained in a coronary CT angiogram, FAI analyzes the fat immediately surrounding the coronary arteries and looks for changes associated with inflammation. When combined with detailed coronary plaque analysis using Canon Medical’s Vitrea Advanced Visualization and CT SUREPlaque, this can provide a more comprehensive picture of coronary artery health than a traditional calcium score or CT Angiography alone.
For many years, we thought of coronary artery disease primarily as a plumbing problem. The theory was straightforward: cholesterol builds up inside an artery, the artery becomes narrower, and eventually the narrowing becomes severe enough to cause a heart attack. We now know that coronary artery disease is considerably more complicated.
Some plaques produce substantial narrowing but remain relatively stable. Other plaques may cause only moderate narrowing but contain characteristics that make them more unstable and vulnerable to rupture. When an unstable plaque ruptures it exposes the inside of the plaque to the blood flow in the artery and causes a blood clot to form at the site of the rupture. It is this clot, not the plaque itself that suddenly blocks blood flow to the heart muscle. This is why simply asking “How blocked is the artery?” doesn’t tell the entire story and why waiting until a blockage is severe enough to show up on a stress test or cardiac catheterization is too late.
A more complete evaluation also needs to consider how much plaque is present, what type of plaque is present, and whether there are signs of inflammation around the artery that indicates a higher likelihood of plaque rupture.
Inflammation plays a central role in the development and progression of atherosclerosis. When inflammation develops within an atherosclerotic plaque, it can contribute to weakening of the fibrous cap covers the plaque and separates it from the bloodstream. Inflamed plaque may then be more susceptible to rupture.
The challenge is that inflammation inside the coronary artery cannot ordinarily be seen directly with a conventional CT scan. But there is an intriguing indirect clue. The coronary arteries are surrounded by a layer of fat called perivascular adipose tissue. Scientists have discovered that inflammation in the artery can change the characteristics of this neighboring fat.
Inflammatory signals released from the artery affect the fat immediately surrounding it. These changes alter the composition and water content of the fat, which in turn changes how it appears on a CT scan. That change can be measured. This is the principle behind the fat attenuation index. As inflammation alters the surrounding fat, its density, or CT attenuation, changes.
Research has demonstrated that higher peri-coronary FAI is associated with features of inflamed vulnerable coronary plaque and with increased cardiovascular risk. A systematic review and meta-analysis involving almost 7,800 patients found that FAI was higher around unstable plaques and that elevated FAI was associated with an increased risk of heart attacks. More recent research has continued to support the association between elevated FAI, total amount of non-calcified plaque present in the arteries, vulnerable plaque characteristics and cardiovascular risk.
FAI represents a next step in the evolution of cardiac imaging for detecting heart attack risk.
A simple scan to measure the coronary calcium score is extremely useful—but it answers a relatively specific question: How much calcified plaque is present? But calcified plaque is thought to be more stable and less likely to be the culprit that leads to plaque rupture.
A coronary CT angiogram can provide considerably more information. It can show both calcified and the more concerning non-calcified plaque, the degree of narrowing present and most importantly be able to follow the progression of plaque over time to determine if treatment has succeeded in stopping new plaque formation.
FAI adds another dimension: Is there evidence of an inflammatory environment surrounding the coronary artery? This distinction matters because not all plaque behaves the same way. A patient with a relatively modest calcium score may still have non-calcified plaque. Conversely, someone with substantial calcification may have predominantly stable, heavily calcified disease. The combination of plaque assessment and inflammatory assessment therefore has the potential to provide a much more complete picture than either measurement alone.
Instead of simply looking at a coronary CT image and asking whether there is a blockage, advanced AI analysis can help quantify several characteristics of the coronary artery and its surrounding tissues. That is important because quantitative measurements can reveal information that may be difficult to appreciate by simply looking at the images.
FAI should not be viewed as a crystal ball that can predict exactly which plaque will rupture or exactly when someone will have a heart attack. Instead, it provides additional information about coronary inflammation and cardiovascular risk. For that reason, FAI should be considered one component of a comprehensive cardiovascular assessment, not a stand-alone test.
At Princeton Longevity Center, our philosophy is to look for and treat cardiovascular disease before it becomes symptomatic and before it reaches a high risk for heart attacks or strokes. That means going beyond a single number. A comprehensive cardiovascular assessment can bring together information such as:
Traditional risk factors:
Cholesterol, blood pressure, diabetes, smoking, family history and other clinical factors.
Coronary calcium:
An assessment of the amount of calcified plaque.
Coronary CT angiography:
A detailed evaluation of the coronary arteries and both calcified and non-calcified plaque.
Plaque analysis:
Quantification of plaque burden and characteristics that may be associated with increased risk and can be used to individualize treatment to stop further plaque progression
Perivascular fat analysis:
Assessment of the CT characteristics of fat surrounding the coronary arteries as an imaging marker associated with local inflammation.
The goal is not simply to discover that someone has coronary artery disease. The goal is to understand what kind of disease they have and how aggressively their cardiovascular risk should be addressed.
Depending on the individual’s overall clinical picture, that could lead to greater emphasis on LDL reduction, blood pressure control, diabetes prevention or treatment, smoking cessation, exercise, nutrition, weight management and other evidence-based strategies for reducing cardiovascular risk.
The most important point is that a scan does not replace clinical judgment—it gives the physician more information on which to base that judgment.
For decades, cardiovascular screening has focused primarily on identifying risk factors and detecting significant arterial narrowing. Modern cardiac CT is able to provide a much richer picture. We can now quantify plaque. We can characterize plaque. We can assess the coronary artery itself. And emerging techniques such as perivascular fat attenuation analysis allow us to investigate the inflammatory environment surrounding the artery. With measurement of FAI we can move from “do I have plaque” to “what is the biological state of my arteries”. This represents an important evolution in preventive cardiology, from measuring risk factors to directly detecting disease to characterizing the biology of that disease. That information can help you and your physician make more informed decisions about prevention—potentially years before coronary disease becomes a heart attack.
At Princeton Longevity Center, we believe that this type of detailed information can be particularly valuable for patients who want to take a proactive approach to their cardiovascular health. Heart disease can develop silently for years. If you are concerned about your cardiovascular risk, consider whether coronary CT angiography and advanced plaque and perivascular fat analysis are appropriate for you. Early knowledge creates the opportunity for earlier action.