Learn · Part 1. Foundations · 4 min read
The big picture
Why the clinical question comes before the test, and how anatomy and function differ.
60-second take
- Decide what you need to learn first: is there coronary disease and where (anatomy), or is the muscle short of blood under stress (function)?
- CCTA, calcium scoring and invasive angiography mostly answer the anatomy question. Exercise ECG, stress echo, SPECT, PET and stress MRI mostly answer the function question.
- Obstructive means a stenosis of 50% or more. Nonobstructive plaque still matters because it is treated with prevention.
- A normal result answers only the question that test asked.
Start with the question, then pick the test
Most confusion about “which test?” comes from skipping a step. Before choosing between a treadmill, an echo, a nuclear scan, a PET, an MRI or a CT, it helps to ask what you need to learn. The 2021 chest pain guideline frames the choice this way: it depends on the clinical question, which is either to establish the diagnosis of coronary artery disease and define the coronary anatomy, or to assess how severe the ischemia is, particularly in patients more likely to have ischemia, those with an abnormal resting ECG, and those who cannot exercise maximally .
“Is there coronary disease, and where?”
Anatomy and plaque
- Coronary CT angiography (CCTA)
- Coronary artery calcium (CAC) score
- Invasive coronary angiography
“Is the heart muscle short of blood under stress?”
Function and ischemia
- Exercise ECG
- Stress echocardiography
- Stress SPECT or PET perfusion imaging
- Stress cardiac MRI
What “anatomy” does and does not tell you
By convention, “obstructive” coronary disease means a stenosis of 50% or more, and “nonobstructive” means less than 50%. The same guideline uses “high-risk CAD” for left main stenosis of 50% or more, or anatomically significant three-vessel disease (stenosis of 70% or more) . Nonobstructive plaque still matters, because it can be treated with preventive therapy even though it does not need a stent or bypass .
CCTA can show the extent and severity of both nonobstructive and obstructive disease and the makeup of the plaque. A computed estimate of fractional flow reserve (FFR-CT) can add an estimate of whether a particular narrowing causes ischemia. Typical effective radiation doses for CCTA are around 3 to 5 mSv .
Invasive angiography defines how severe a narrowing is and where it sits. Its main purpose is to decide whether revascularization is feasible and needed, and pressure-wire measurements (FFR or iFR) add functional information. Its resolution, about 0.3 mm, cannot show the 0.1 mm arterioles that regulate muscle blood flow, so a normal angiogram does not rule out abnormal coronary vascular function .
What “function” does and does not tell you
Stress tests work by raising the heart’s demand for blood, or by dilating the coronary arteries, and watching what happens. If the arteries cannot raise their flow enough to meet the demand, the mismatch produces ischemia . An ischemic response shows a physiological consequence of disease, which is something anatomy alone cannot show. The next lessons explain how.
The appropriate use criteria that power the scenario builder rate each test for each clinical scenario, so the same patient can see different ratings for the same test depending on whether the question is detection, risk assessment, or follow-up of known disease. The 2023 multimodality criteria cover the detection and risk assessment of chronic coronary disease. Evaluation before noncardiac surgery has its own criteria .
The criteria do not rank the tests against each other. Your patient’s symptoms, prior test results, ability to exercise and the contraindications that apply all shape which test is reasonable, and that is what the scenario builder walks through.
Try the scenario builder → to see how the published criteria rate each test for a patient like yours.
Try it in the tool
Sources cited on this page
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