Cardiology · Coronary Artery Stenosis

Diagnosing Coronary Stenosis: Scans and Tests

At a Glance

Coronary stenosis is usually assessed first with noninvasive imaging, especially CCTA. CT-FFR or invasive pressure-wire tests such as FFR and iFR can show whether a narrowing truly limits blood flow and guide decisions about medication, stenting, or further testing.

The journey to diagnosing coronary stenosis has changed significantly in recent years. Doctors no longer rely solely on your description of chest pain; instead, they use a structured pathway to determine if your heart’s blood supply is truly restricted. This process often starts with estimating your clinical likelihood—a calculation based on your age, sex, and risk factors to decide if testing is even necessary ^[1]^[2].

The First Line: Non-Invasive Scans

For most patients with stable symptoms, the first step is often a non-invasive test rather than going straight to a catheterization lab. Current international guidelines from the European Society of Cardiology (ESC) and the American Heart Association (AHA) emphasize that imaging is generally preferred over a simple exercise treadmill test (ECG), although an exercise ECG remains a reasonable choice for selected patients ^[1]^[3].

Coronary Computed Tomography Angiography (CCTA)

CCTA is a specialized heart scan that uses X-rays and contrast dye to create detailed 3D images of your coronary arteries.

Strengths: It is incredibly effective at “ruling out” large-vessel disease in appropriate patients with good image quality. If a CCTA shows clear arteries, there is roughly a 95% certainty that you do not have significant obstructive disease ^[4]^[5].
Plaque Visualization: Unlike older tests, CCTA allows doctors to see the actual plaques inside your artery walls, even if they aren’t causing a major blockage yet ^[6].
Limitations: It is less accurate if your arteries are heavily calcified (hardened by calcium), as the calcium can create “blooming” artifacts that make blockages look worse than they are. A normal CCTA also does not definitively rule out microvascular disease or vasospasm ^[7].

CT-FFR: The New Non-Invasive Physiology Test

One of the newest tools in cardiology is CT-FFR (Computed Tomography-derived Fractional Flow Reserve). This technology uses powerful computer software to analyze your CCTA images and estimate the actual blood pressure and flow across a blockage ^[8].

How it’s used: If a CCTA shows a “maybe” or “intermediate” blockage (usually between 30% and 70%), CT-FFR can help determine if that blockage is actually starving the heart of oxygen without needing an invasive procedure ^[9].
Threshold: A CT-FFR value of 0.80 or less often indicates that the narrowing is significantly limiting blood flow, helping doctors decide if further invasive testing is needed ^[10].

The Reference Standard: Invasive Coronary Angiography

If non-invasive tests suggest a serious problem, or if your symptoms are very high-risk, your doctor may recommend an Invasive Coronary Angiography (ICA). This involves threading a thin tube (catheter) through a blood vessel in your wrist or groin up to your heart to take “live” X-ray movies of your blood flow ^[11]. While generally safe, ICA is an invasive procedure and carries small risks, including bleeding, contrast reaction, kidney injury, stroke, or heart attack.

Measuring “Functional Significance” (FFR and iFR)

Sometimes, a blockage looks severe on the X-ray, but the heart is actually getting plenty of blood. To be sure, doctors use a tiny pressure wire to take precise measurements inside the artery ^[12].

FFR (Fractional Flow Reserve): This is measured while your heart is in a state of “maximum stress,” usually stimulated by a medication called adenosine. An FFR of ≤ 0.80 is the standard threshold; if the number is higher than 0.80, the blockage is often considered “non-ischemic,” meaning it may be safely treated with medication rather than a stent ^[13]^[14].
iFR (Instantaneous Wave-Free Ratio): This is a newer measurement that does not require stress-inducing medication. It measures the pressure during a specific quiet moment in the heart’s cycle. The standard threshold for iFR is ≤ 0.89 ^[13]^[15].

These thresholds are highly useful decision aids, though they are not absolute rules. Values near the cutoff, or situations involving complex disease, require clinical interpretation. Clinical trials have shown that using these pressure-wire measurements to guide treatment—rather than just looking at the “clog” on a screen—leads to better patient outcomes and avoids unnecessary procedures ^[14]^[16]. Regardless of which test you have, the goal is to determine not just if a blockage exists, but if it is actually affecting your heart’s ability to function ^[17].

Common questions in this guide

What test is usually done first to check for coronary stenosis?

For many people with stable symptoms, doctors start with a noninvasive test, often coronary CT angiography (CCTA), rather than catheterization. An exercise ECG may still be appropriate for selected patients based on their symptoms, risk, and overall health.

What can a coronary CT angiogram show?

A CCTA uses X-rays and contrast dye to create detailed images of the coronary arteries. It can show plaque and is especially useful for ruling out significant large-vessel blockage when the images are clear, but heavy calcium can make narrowing look worse than it is, and a normal scan does not rule out every cause of chest pain.

What does a CT-FFR result of 0.80 or lower mean?

CT-FFR uses computer analysis of a CCTA to estimate blood flow across a narrowing. A value of 0.80 or lower often suggests that the narrowing may be significantly limiting blood flow and may help determine whether invasive testing is needed.

What do FFR and iFR measure during an angiogram?

FFR and iFR use a pressure wire to measure how much a coronary narrowing affects blood flow. An FFR of 0.80 or lower or an iFR of 0.89 or lower commonly suggests a flow-limiting blockage, although results near the cutoff need to be interpreted in the context of the whole clinical picture.

What are the risks of invasive coronary angiography?

Invasive coronary angiography is generally safe but involves passing a catheter through a blood vessel to the heart. Possible risks include bleeding, a reaction to contrast dye, kidney injury, stroke, and heart attack, so doctors weigh the potential benefit against these risks before recommending it.

Why might my doctor use FFR or iFR instead of judging a blockage by its appearance?

A narrowing that looks severe on an X-ray may not actually reduce blood flow enough to affect the heart. FFR or iFR provides a direct pressure-based assessment that can help doctors decide whether medication is reasonable or whether a stent or another procedure should be considered.

Curated prompts to bring to your next appointment.

1.Based on my age, symptoms, and risk factors, what is my estimated clinical likelihood of having obstructive coronary artery disease?
2.Does my CCTA report provide a CAD-RADS score, and what does it indicate about the severity of my plaque?
3.If my CCTA showed a blockage, was a non-invasive CT-FFR calculation performed to see if the blockage actually limits blood flow?
4.If we proceed to an invasive angiogram, will you use a pressure wire to measure FFR or iFR if you find an intermediate-level blockage?
5.In my case, what are the specific benefits of an anatomical test like a CCTA versus a functional test like a stress echo or nuclear scan?

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Key takeaways

For many people with stable symptoms, noninvasive imaging—often CCTA—is preferred before invasive angiography, although an exercise ECG can suit selected patients.
CCTA can show plaque and help rule out significant large-vessel blockage when image quality is good, but calcium, microvascular disease, and vasospasm can limit interpretation.
CT-FFR analyzes a CCTA to estimate whether an intermediate narrowing limits blood flow; a value of 0.80 or lower often suggests significant flow limitation.
During invasive angiography, FFR of 0.80 or lower and iFR of 0.89 or lower are common thresholds for a flow-limiting blockage, but values near the cutoffs require clinical context.
Pressure-wire measurements can help determine whether a blockage may need a stent or can be managed with medication, helping avoid unnecessary procedures.

References (17)

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This page explains tests used to evaluate coronary stenosis for informational purposes only and does not replace medical advice. Your cardiology team can recommend the safest test and interpret your results.

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