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PubMed This is a summary of 18 peer-reviewed journal articles Updated
Cardiology

Testing and Imaging: Identifying Your Level of Risk

At a Glance

Doctors choose coronary atherosclerosis tests based on symptoms and risk: CAC estimates calcified plaque, CCTA shows plaque and artery narrowing, stress tests assess blood flow during exertion, and invasive angiography is reserved for high-risk or emergency situations.

The process of diagnosing coronary atherosclerosis has evolved from simply looking for “blockages” to understanding your total plaque burden and future risk. Doctors use a tiered approach, starting with non-invasive tests to determine whether you need preventive care, more advanced imaging, or an invasive procedure [1].

Screening in Asymptomatic Patients: The CAC Score

If you do not have symptoms like chest pain or shortness of breath, clinical risk assessment is usually the first step. When the decision to start preventive medication is still uncertain, doctors may selectively use a Coronary Artery Calcium (CAC) score. This is a quick, low-radiation CT scan that measures the amount of calcified (hardened) plaque in your coronary arteries [2].

  • Score of 0: Often called a “Power of Zero,” this indicates a substantially lower risk of a heart event over the next 10 years [3][2]. In primary prevention settings, a score of 0 often supports withholding or deferring statin therapy in appropriate patients [4]. However, a 0 does not mean zero risk. It does not reliably exclude soft plaque [5][6], and it should not generally override the need for treatment if you have established clinical coronary disease, severe LDL-C (above 190 mg/dL), diabetes, or a strong premature family history.
  • Score of 1–99: This indicates a mild amount of plaque. It generally confirms that atherosclerosis has begun and usually shifts the conversation toward lifestyle changes and preventive medications [7][8].
  • Score of 100 or Higher: A score above 100 (or above the 75th percentile for your age and sex) signals a significantly higher risk [9]. At this level, guidelines strongly support statin initiation and other preventive therapies [4][8].

Diagnosis in Symptomatic Patients: CCTA and Stress Tests

If you do have symptoms, a calcium score is usually not enough. Doctors need to see if the plaque is actually narrowing the artery or causing a lack of blood flow to the heart muscle.

  • Coronary CTA (CCTA): This is a specialized CT scan that uses intravenous contrast (dye) to create a detailed 3D map of your arteries [10]. It is highly effective at ruling out “obstructive” disease (blockages greater than 50%). CCTA can also see soft plaque and high-risk features [11][12]. However, CCTA is not automatically for everyone—it depends on your kidney function, contrast allergy, heart rate, and calcium burden.
  • Functional Stress Testing: These tests (such as a treadmill test, stress echo, or nuclear stress test) don’t look directly at the anatomy. Instead, they measure how your heart functions under stress [13]. They are used to find inducible ischemia—evidence that a part of your heart is not getting enough oxygen [14].

The Role of Invasive Angiography

An Invasive Coronary Angiogram (cardiac catheterization) involves threading a small tube through an artery in your wrist or groin up to your heart. While it is the “gold standard” for accuracy, it is not a screening tool and is not the default first test for stable suspected CAD [13][15].

Invasive angiography is typically reserved for “high-risk” situations, such as:

  1. Symptoms that do not improve with medication [13].
  2. Non-invasive tests (like CCTA or a stress test) that show severe or dangerous blockages [13].
  3. Emergency situations, such as a suspected heart attack [16].

During this procedure, doctors may use a tool called FFR (Fractional Flow Reserve) to measure the actual pressure drop across a blockage [17]. FFR measures whether the narrowing limits flow, but it does not measure plaque vulnerability. Invasive angiography carries specific risks, including bleeding, vascular injury, contrast-related kidney injury, and stroke, which should be discussed before the procedure [18][16].

Common questions in this guide

What does a coronary artery calcium (CAC) score tell me?
A CAC score comes from a low-radiation CT scan and estimates the amount of hardened, calcified plaque in the coronary arteries. A higher score generally indicates more plaque and higher future heart risk. A score of 0 lowers risk for many people without known coronary disease, but it does not reliably detect soft plaque.
Does a CAC score of 0 mean I have no heart disease?
No. A zero score does not rule out soft plaque, and it should not generally override recommended preventive treatment when someone has known coronary disease, diabetes, LDL cholesterol above 190 mg/dL, or a strong premature family history. The meaning of the score depends on the person's overall risk and symptoms.
How is a CCTA different from a stress test?
A CCTA uses contrast-enhanced CT to create a detailed picture of the coronary arteries, including plaque and areas of narrowing. A stress test measures how the heart functions under stress and looks for signs that part of the heart muscle may not be receiving enough oxygen. These tests answer different questions and may be used together.
When is an invasive coronary angiogram needed?
An invasive coronary angiogram is not usually used as a screening test or as the first test for stable symptoms. It may be considered when symptoms continue despite medication, a CCTA or stress test shows a severe or dangerous blockage, or an emergency such as a suspected heart attack is occurring. The procedure has risks such as bleeding, blood-vessel injury, kidney injury from contrast, and stroke.
What does FFR show during a coronary angiogram?
FFR measures the pressure change across a coronary narrowing to show whether that narrowing is limiting blood flow. It helps assess the functional effect of a blockage, but it does not measure how vulnerable the plaque is to causing a future event.
What does non-obstructive plaque mean on a scan?
Non-obstructive plaque narrows a coronary artery by less than 50 percent, so it may not be causing a major blockage. It still confirms that atherosclerosis is present and can affect decisions about lifestyle changes and preventive medication. The amount and features of plaque matter in addition to the percentage of narrowing.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Given my age and risk factors, is a CAC score, CCTA, or a stress test the most appropriate next step for me?
  2. 2.If my CAC score is 0, does my clinical profile (like my age, diabetes, or LDL level) suggest I still need preventive medication?
  3. 3.How will my stress test results be used in combination with my imaging to decide if I need more invasive testing?
  4. 4.If my imaging shows non-obstructive plaque (less than 50% narrowing), how does that change my medication and prevention plan?
  5. 5.What are the specific 'high-risk features' on my scan, and what do they actually mean for my treatment?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

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This page is for informational purposes only and does not constitute medical advice. Your clinician should choose and interpret coronary atherosclerosis tests based on your symptoms, risk factors, and medical history.

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