Neither test is the better one, because they answer different questions. A calcium score asks whether plaque has built up in your heart arteries. A stress test asks whether your heart muscle gets enough blood when it works hard.
In general, a calcium score is a test for people who feel well and want to understand their long-term risk. A stress test is a test for people who have symptoms, such as chest discomfort or breathlessness with effort, that might come from a narrowed artery.
Key takeaways
- A calcium score shows whether plaque has built up, while a stress test shows whether the heart gets enough blood under effort.
- Calcium scoring is mainly for people who feel well, and stress testing is mainly for people with symptoms.
- A normal stress test does not mean you have no plaque.
- A calcium score of zero does not rule out a heart cause in someone with symptoms.
- Routine stress testing is generally not recommended for people who feel well, and the evidence for calcium scoring also has limits.
What each test looks for
A calcium score. A coronary artery calcium (CAC) scan is a quick CT scan of the heart with no injection and no contrast dye. It detects calcium in the walls of the coronary arteries. The score is an estimate of how much plaque you have built up over the years.
This is a picture of anatomy. It shows that plaque exists and roughly how much. It does not show whether any single plaque is narrowing an artery, and it does not test how the heart performs. For the full explanation of scores and bands, see our guide to the coronary calcium score.
A stress test. This checks function. You walk on a treadmill, or receive a medicine that mimics exercise, while your heart is monitored. The basic version records an ECG. Other versions add ultrasound or nuclear imaging to watch the heart muscle directly.
The test is looking for ischemia: a part of the heart that does not get enough blood when demand rises. That usually happens only when an artery is narrowed enough to limit flow. Plaque that narrows an artery mildly will not show up, because blood still gets through.
The two tests side by side
| Feature | Calcium score | Stress test |
|---|---|---|
| Question it answers | Do I have calcified plaque, and how much? | Is blood flow to my heart muscle restricted during exertion? |
| What it shows | Anatomy: calcium in the artery wall | Function: how the heart responds to stress |
| Who it is mainly for | Adults without symptoms whose risk is uncertain | People with symptoms that may come from the heart |
| How it is done | CT scan, done in under 15 minutes | Treadmill or medicine, with ECG and sometimes imaging |
| Radiation | About 1 to 1.5 mSv | None for a treadmill ECG or stress ultrasound. Nuclear versions use a radioactive tracer |
| What a normal result does not rule out | Soft plaque that has not calcified | Plaque that does not yet limit flow |
A normal stress test does not mean no plaque
This is the point people most often miss. A stress test can be completely normal in someone with a lot of plaque, as long as none of it is tight enough to limit flow.
One study put numbers on this. Researchers looked at 1,195 patients without known heart disease who had both a nuclear stress test and a calcium scan. Among the 1,119 whose stress test was normal, 56% had a calcium score of 100 or more and 31% had a score of 400 or more.1
A normal stress test is good news about blood flow today. It is not a statement about your long-term risk, and it does not replace treating the causes of plaque.
A calcium score does not replace a stress test either
The reverse is also true. A calcium score cannot tell you whether your chest discomfort comes from your heart. It only counts calcified plaque, and it misses plaque that has not calcified.
In a large registry of people with symptoms who had both a calcium score and a detailed CT angiogram, 3.5% of those with a score of zero still had an artery narrowed by half or more.2 So in a person with symptoms, a zero does not close the question.
The same study that found plaque behind normal stress tests found the mirror image too: restricted blood flow was seen in fewer than 2% of people with scores below 100, and became more frequent as scores rose.
Which one do you need?
If you have symptoms, the calcium score is not the right starting point. Chest pressure, breathlessness on exertion, or pain spreading to the arm or jaw need medical evaluation. US chest pain guidance sets out a separate diagnostic workup for people with symptoms, built on risk assessment and shared decision-making.3 If symptoms are severe or sudden, call 911.
If you feel well, a routine stress test is generally not recommended. The US Preventive Services Task Force recommends against screening with a resting or exercise ECG in adults without symptoms who are at low risk of cardiovascular disease.4 Its reasoning is that the result is very unlikely to change treatment, and false alarms can lead to invasive follow-up tests. For people at intermediate or high risk, it found the evidence insufficient either way.
A calcium score is the test more often considered in people without symptoms, usually when a risk estimate lands in a gray zone and the result would change what you do. Even here the evidence has limits. The same task force found the evidence insufficient to judge whether adding a calcium score to standard risk assessment improves outcomes.5
Some people end up needing both. A person with a high calcium score who later develops symptoms may be sent for a stress test. Our guide to a high calcium score explains how that decision is made.
Where each test fits with Cardio Res-Q
Cardio Res-Q is built for prevention in people without acute symptoms. The Enhanced Assessment ($999) includes a calcium score and a CIMT ultrasound on top of Dr. Varano's clinical evaluation and advanced labs. The calcium scan is ordered by your provider and done at an outside imaging facility as a separate self-pay study, typically $100 to $200.
Neither Cardio Res-Q assessment lists a stress test. If your history or symptoms suggest you need one, that belongs with a cardiologist, and Cardio Res-Q is not a replacement for that visit. Read Cardio Res-Q vs. a cardiologist visit to see who does what, or go to the Cardio Res-Q program page to book an assessment.
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
I passed a stress test. Do I still need a calcium score?
Possibly, because the two tests measure different things. A normal stress test says blood flow was adequate under stress. It does not show how much plaque you have. Whether a calcium score would change your treatment is the question to ask your clinician.
My calcium score is zero. Do I need a stress test?
If you have no symptoms, generally not. If you do have symptoms, a zero score does not rule out a heart cause, and your doctor may still want functional testing or a CT angiogram.
Which test has more radiation?
A calcium scan uses a small dose, about 1 to 1.5 mSv.6 A treadmill ECG or stress ultrasound uses none. Nuclear stress tests do involve radiation from a tracer, and the amount depends on the protocol, so ask the imaging center.
Can a stress test predict a heart attack?
Not reliably in a person without symptoms. It finds flow-limiting narrowing, which is only part of the picture. Long-term risk depends more on total plaque and on risk factors such as cholesterol particles, blood pressure, blood sugar and smoking.
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.
