A calcium score and a coronary CT angiogram both use a CT scanner to look at the arteries of your heart, but they are different tests. A calcium score is a quick scan with no injection that adds up calcified plaque. A CT angiogram uses contrast dye given through an IV to show the inside of the arteries, including soft plaque and narrowing.
They are also meant for different people. The calcium score helps sort risk in adults who feel well. The CT angiogram is mainly a diagnostic test for people with symptoms such as chest pain. Cardio Res-Q includes a calcium score in its Enhanced Assessment. It does not offer CT angiography.
Key takeaways
- A calcium score needs no IV and no dye, while a CT angiogram needs both.
- Only the angiogram can show plaque that has not calcified and how much an artery is narrowed.
- Trial evidence supports CT angiography for people with chest pain, not as a screening scan for people without symptoms.
- For an adult with no symptoms who is weighing prevention, the calcium score is the usual first scan.
- If you need a CT angiogram, it is arranged through a cardiologist or your own doctor, not through Cardio Res-Q.
How each scan works
Calcium score. You lie on the scanner table, hold your breath for a few seconds, and you are done. There is no needle. Software adds up the calcium in the walls of your coronary arteries and reports one number. Our guide to the coronary calcium score explains the score bands.
CT angiogram. This scan is often called CCTA or coronary CTA. A nurse places an IV, and iodine-based contrast dye is injected while the scanner takes images. The dye fills the arteries so the open channel and the artery wall can both be seen. You may be given medicine to slow your heart rate so the pictures are sharp, and your kidney function is usually checked first because the kidneys clear the dye.
Calcium score and CT angiogram side by side
| Feature | Calcium score | CT angiogram |
|---|---|---|
| Contrast dye and IV | None | Both required |
| What it shows | Amount of calcified plaque | Calcified and non-calcified plaque, and how narrow each artery is |
| Result | A single score | A written report, artery by artery |
| Radiation | About 1 to 1.5 mSv | Usually more, and it varies widely by scanner and hospital |
| Mainly used for | Adults without symptoms whose risk is uncertain | People with symptoms that may come from the heart |
| Main drawback | Cannot see soft plaque or narrowing | Dye, more preparation, more incidental findings to chase |
| Available through Cardio Res-Q | Yes, at an outside imaging facility | No |
What the angiogram sees that the calcium score cannot
Plaque starts soft and picks up calcium later. A calcium scan only counts the calcified part, so a score of zero does not prove the arteries are clean. Our comparison of soft and calcified plaque covers the biology.
How often does a zero hide something? One large registry looked at more than 10,000 people with symptoms who had both scans. Among those with a calcium score of zero, 84% had no coronary disease on the angiogram, 13% had plaque that did not block flow, and 3.5% had an artery narrowed by half or more.1
So in most people a zero does mean little or no plaque. But if you have chest pain or breathlessness on exertion, a calcium score of zero is not enough to rule out a problem.
Dye and radiation: the trade-offs
Contrast dye. Reactions are uncommon and usually mild. In a hospital review of 137,473 contrast CT scans, 0.31% of patients had an acute reaction, most of them mild, and 0.01% had a severe one.2 Tell the imaging team about any earlier reaction to contrast and about kidney disease.
Radiation. A calcium scan involves about 1 to 1.5 mSv. A CT angiogram covers the same area in more detail and generally uses more. An international survey of 61 hospitals found that angiogram doses had fallen by 78% over ten years, yet the typical dose still differed 37-fold between the lowest and highest hospitals.3
Who each test is for
If you have symptoms. The best evidence for CT angiography is here. In a Scottish trial of 4,146 patients with stable chest pain, adding a CT angiogram to standard care lowered the five-year rate of heart attack or death from heart disease from 3.9% to 2.3%.4 The researchers noted that more people in the scan group started preventive treatment. Stress testing is another route for people with symptoms, and your cardiologist chooses between them.
If you have no symptoms. Screening with CT angiography has not been shown to help. In a randomized trial of 900 adults with diabetes and no heart symptoms, screening with CT angiography did not reduce the combined rate of death, heart attack or hospital admission for unstable angina over four years.5 That is why the simpler calcium score, not the angiogram, is the scan used when a prevention decision is uncertain.
The calcium score has limits of its own. The US Preventive Services Task Force concluded in 2018 that the evidence was insufficient to judge the balance of benefits and harms of adding a calcium score to standard risk assessment in adults without symptoms.6 It is a tool for a specific decision, not a test everyone needs.
Can a calcium score lead to an angiogram?
Sometimes. A high score does not by itself mean you need more imaging, because the usual response is tighter control of risk factors. A clinician may suggest a stress test or a CT angiogram if a high score comes with symptoms or other warning signs. See what happens after a high calcium score.
The calcium score in a Cardio Res-Q assessment
The Enhanced Assessment ($999) includes a coronary calcium score and a CIMT ultrasound along with Dr. Varano's clinical evaluation and advanced labs. Your provider orders the calcium scan, and you have it at an outside imaging facility as a separate self-pay study, typically $100 to $200.
Cardio Res-Q does not perform or include CT angiography. If your results or symptoms point toward one, that decision belongs with a cardiologist, and our team can share your results with them. To compare the two entry options, read the $775 and $999 assessments compared, or go to the Cardio Res-Q program page.
Are You a Candidate for Cardio Res-Q?
Three quick questions about the risk factors we screen for. Your answers stay between you and the clinic.
Frequently asked questions
Is a CT angiogram better than a calcium score?
It shows more, but more detail is not always more useful. For someone with chest pain, the extra detail can change care. For someone with no symptoms, trials have not shown that the extra detail improves outcomes, and it comes with dye, more radiation and more findings that may need follow-up.
Does a CT angiogram also give a calcium score?
Many centers run a calcium scan first, in the same visit, before injecting dye. Not all do, so ask the imaging center if you want the score reported.
My calcium score is zero. Should I still get an angiogram?
If you feel well, a zero score is generally reassuring and an angiogram is not the usual next step. If you have symptoms, tell your doctor, because a zero score does not fully rule out narrowing in people with symptoms.
Related reading
This article is for general education and is not medical advice. Decisions about testing and medication should be made with your clinician. If you have chest pain or other symptoms of a heart attack, call 911.
