CT coronary angiography: when imaging helps and when it doesn’t
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CT coronary angiography, often shortened to CTCA, is a heart scan that allows doctors to look directly at the coronary arteries that supply blood to the heart muscle.
It is sometimes described as a more detailed evolution of the calcium score. Used thoughtfully, it can add valuable clarity. Used indiscriminately, it can add little and sometimes confuse decision-making.
This page explains what CT coronary angiography is, how it differs from a calcium score, and when it is most useful in prevention.
This article is part of our wider ASCVD (heart disease and stroke) resource hub, which brings together all our guidance on cardiovascular prevention in one place.
What CT coronary angiography actually shows
CT coronary angiography uses a CT scanner and contrast dye to create detailed images of the coronary arteries.
Unlike standard cholesterol tests, which infer risk indirectly, CTCA allows direct visualisation of:
- the artery walls
- the presence of plaque
- whether plaque is calcified or soft
- whether plaque is narrowing the artery
This matters because atherosclerosis begins in the artery wall long before it causes symptoms or significant narrowing.
How CT coronary angiography differs from a calcium score
A coronary artery calcium (CAC) score is a simpler CT scan that looks only for calcified plaque.
Calcification is a marker of past plaque activity. Its presence tells us that atherosclerosis has already occurred. However, early and potentially unstable plaque is often not calcified and therefore not visible on a calcium score.
CT coronary angiography includes a non-contrast scan similar to a calcium score, but then adds contrast imaging that shows the artery walls and soft plaque as well.
For this reason, CTCA often provides more complete information than a calcium score alone.
In many cases, particularly for people who want a clearer understanding of early disease or who are deciding how proactive to be with long-term prevention, it can make sense to go straight to CT coronary angiography rather than doing a calcium score first.
Read more about atherosclerotic cardiovascular disease and how plaque develops
When imaging is most helpful
Imaging is most useful when the results would meaningfully change what you do next.
CT coronary angiography may be helpful if you:
- have elevated ApoB or inherited risk such as lipoprotein(a)
- have a family history of early heart disease
- are uncertain how aggressively to manage long-term risk
- want reassurance that goes beyond short-term risk calculators
It is generally less helpful if you already know you want to pursue maximal prevention regardless of the result.
Limitations and considerations
CT coronary angiography involves exposure to a small amount of ionising radiation and the use of contrast dye.
For most people, the radiation dose is low and comparable to background exposure. Contrast is generally safe but requires caution in people with impaired kidney function or contrast allergies.
As with any test, the key question is not whether it can show something, but whether what it shows will change management.
How CT coronary angiography fits into prevention
CT coronary angiography does not replace blood tests or lifestyle assessment. It complements them.
Blood markers such as ApoB help estimate exposure and future risk. CTCA shows whether plaque is already present and provides context for how aggressively prevention should be pursued.
Importantly, a normal CT coronary angiogram does not mean risk is zero. It means that significant plaque is not currently visible. Prevention still focuses on reducing cumulative exposure over time.
What to take away
CT coronary angiography can be a powerful tool when used thoughtfully.
The key points are:
- it allows direct assessment of coronary arteries
- it can detect plaque earlier than a calcium score alone
- it is most useful when results will change decisions
- it should be interpreted alongside blood markers and overall risk
If you are considering imaging and want help deciding whether a calcium score or CT coronary angiography is more appropriate for you, we can help guide that decision and arrange appropriate testing as part of a broader prevention strategy.
If you would like to go deeper:
Download the 2-page heart attack and stroke prevention guide