Two different CT-based heart scans are used to look for coronary artery disease before symptoms appear: coronary artery calcium (CAC) scoring, a quick screening test that estimates plaque buildup as a single number, and coronary CT angiography (CCTA), a more detailed scan using contrast dye that can actually see blockages. They answer different questions, and knowing which is which matters — they're often used as different steps in the same evaluation, not interchangeable versions of the same test.
Why This Matters, Especially Without Symptoms
Coronary artery disease can build silently for years before causing any symptoms, and for some people the first "symptom" is a heart attack itself. These scans are specifically designed to catch disease before that happens, in the right candidates — which is the entire premise behind community screening programs like the county-wide coronary CT angiography program that finds and helps treat asymptomatic coronary disease before it becomes an emergency.
Coronary Artery Calcium (CAC) Scoring
What It Is A quick, non-contrast CT scan — no IV, no dye — that detects and measures calcium deposits in the walls of your coronary arteries. Calcium is a marker of atherosclerosis (plaque buildup) that has accumulated over years.
How It Works The scan produces a single number, the Agatston score (your "CAC score"), starting at 0 and going up. General categories:
- 0 — no detectable calcified plaque, generally favorable
- 1–99 — mild
- 100–399 — moderate
- 400+ — extensive
Your doctor interprets your specific number in the context of your overall risk factors — not as a stand-alone verdict.
Who It's For Typically used in people without symptoms who are at intermediate cardiovascular risk based on traditional risk factors (age, blood pressure, cholesterol, family history, and so on). It helps refine that risk estimate and guide decisions like whether to start a statin. It's generally not used in people who already have known coronary disease, or who are already clearly very low or very high risk by other measures, since it adds less useful information in those cases.
What to Expect Takes only a few minutes. No contrast dye or IV needed. Minimal radiation exposure, in the range of a mammogram. No fasting or special prep typically required — one of the logistically simplest tests on this site.
What Your Score Means A score of zero is reassuring but not an absolute guarantee — it means calcified plaque wasn't detected, though very early, non-calcified (soft) plaque can still be present in a small number of people. A higher score indicates more established atherosclerosis and typically prompts a more proactive conversation about risk factor management, and sometimes further testing.
Coronary CT Angiography (CCTA)
What It Is A more detailed CT scan that uses IV contrast dye to directly visualize the inside of your coronary arteries. Unlike calcium scoring, which only detects calcium, CCTA can see actual blockages — including "soft," non-calcified plaque that a calcium score would miss entirely.
How It Works Contrast dye is injected through an IV, and specialized CT imaging captures detailed pictures of your coronary arteries. A medication to slow your heart rate is sometimes given beforehand to improve image quality. The scan itself takes just a few seconds, though the full appointment takes longer once prep is included.
Who It's For Used both in patients with symptoms concerning for coronary disease — as a non-invasive alternative to catheterization in appropriate patients — and, in a screening context like a community CCTA program, in asymptomatic patients at higher risk who would benefit from directly seeing whether blockages exist, not just whether calcium is present.
What to Expect An IV is placed. You may be given a beta-blocker to slow your heart rate and/or nitroglycerin to open the coronary arteries for better imaging. Contrast dye is injected — a brief warm sensation is common and normal — and you'll need to hold your breath briefly during image capture. Mild prep restrictions (avoiding caffeine, sometimes a fasting window) are typical beforehand; your center will give you specific instructions.
What Results Mean Results describe whether blockages are present, their location, and generally their severity — how much they narrow the artery. This level of detail can directly guide whether medication alone is appropriate or whether a procedure like PCI should be considered — see Procedures & Devices.
Which One Do I Need? (Comparison)
| CAC Scoring | CCTA | |
|---|---|---|
| Contrast/IV | No | Yes |
| What it measures | Calcium burden (a single risk number) | Actual blockages, including non-calcified plaque |
| Best for | Refining risk in people without symptoms at intermediate risk | A specific question about whether a blockage exists — symptoms, or higher-risk screening |
| Time/prep | Minutes, minimal prep | Longer appointment, some prep restrictions |
Some programs use calcium scoring as an initial, lower-cost, lower-radiation filter, and reserve CCTA for patients whose risk profile or calcium score suggests a closer look is warranted — though this varies by program and your doctor's judgment. You generally don't need both automatically; the right test (or sequence) depends on your specific risk profile and the question being asked.
Lifestyle & Follow-Up
Regardless of which test you have or what it shows, your result is a starting point for a risk-reduction conversation, not just a number — see Heart-Healthy Eating, Exercise, Hyperlipidemia, Hypertension, and Medications 101 for statins. A meaningful score on either test often prompts your doctor to be more proactive about risk factor treatment even without symptoms.
Living With Your Results
Many people feel real anxiety after learning they have "some" plaque, even at a low level. Try to hold two things at once: this information is genuinely useful for prevention, and having detectable plaque at a low level is common and, with treatment, very manageable. A zero calcium score is reassuring but not a permanent pass — risk factors and repeat testing over time still matter.
Common Questions
Do I need both tests?
Not usually — your doctor recommends the one (or sequence) that fits your specific risk profile and question, not both automatically.
Is the radiation dangerous?
Both tests use low-dose imaging, and CAC scoring in particular is quite low. Your doctor weighs this against the value of the information for your specific situation.
What if my calcium score is zero but I still have symptoms?
A zero score doesn't fully rule out disease if you have symptoms — report symptoms directly, since further testing (including CCTA or other options) may still be appropriate regardless of a favorable screening score.
Can I request this test myself?
Availability and appropriateness criteria vary — ask your doctor whether you're a good candidate given your specific risk factors, since these tests work best when targeted to the right population rather than applied universally.
How often should I repeat it?
This depends on your initial result and risk factors — ask your care team for a personalized interval rather than assuming a fixed schedule applies to everyone.