EndoPAT and a stress test measure different things. EndoPAT checks how well small arteries widen when blood flow surges, which reflects the health of the vessel lining. A stress test checks whether your heart muscle gets enough blood when it is made to work hard.
Neither test looks for early plaque, and neither is recommended as a general screening test for people who feel well. A stress test is mainly for people with symptoms. EndoPAT is used selectively. Our clinic offers EndoPAT when it is indicated and does not offer stress testing.
Key takeaways
- EndoPAT is a fingertip test of vessel lining function, and a stress test looks for reduced blood flow to the heart during exertion.
- A normal result on either one does not mean your arteries are free of plaque.
- The FDA clearance for EndoPAT states that it is not meant for screening the general population.
- US prevention guidance advises against exercise ECG screening in low-risk adults without symptoms.
- Chest pain or breathlessness with exertion calls for a medical evaluation, not an EndoPAT.
What EndoPAT measures
The endothelium is the thin lining of your blood vessels. A healthy lining signals the vessel to relax and widen when more blood is needed. When that response is weak, it is called endothelial dysfunction.
During EndoPAT, sensors sit on a fingertip of each hand. A blood pressure cuff on one arm is inflated for about five minutes and then released. The device compares the surge in pulse volume in that finger with the other hand and reports a ratio called the reactive hyperemia index.
In a study of 94 patients who had coronary vessel function measured directly, a low index identified those with coronary endothelial dysfunction with a sensitivity of 80% and a specificity of 85%.1 That is a small study in a selected group, so it shows what the test is tracking more than how it performs in everyday use. Our EndoPAT guide covers the outcome studies and the limits.
What a stress test measures
A stress test raises the heart's workload, with a treadmill or with medicine, while an ECG and sometimes imaging watch the response. It is looking for ischemia: heart muscle that runs short of blood when demand goes up. That usually happens only when an artery is narrowed enough to limit flow.
This makes it a test for people with symptoms. In a trial of 10,003 patients with symptoms suggesting coronary disease, most with chest pain or breathlessness on exertion, an initial strategy of stress testing and an initial strategy of CT angiography led to similar outcomes over about two years.2 Plaque that does not yet restrict flow will not show on a stress test. We explain that gap in calcium score vs. stress test.
EndoPAT and stress test side by side
| Feature | EndoPAT | Stress test |
|---|---|---|
| Question it answers | Do my small arteries widen normally? | Does my heart muscle run short of blood under exertion? |
| How it is done | Fingertip sensors and an arm cuff, lying still | Treadmill or medicine, with ECG and sometimes imaging |
| What it reflects | Function of the vessel lining | Flow-limiting narrowing in a coronary artery |
| Mainly used for | Selected people, when a provider thinks it will add information | People with symptoms that may come from the heart |
| Detects early plaque | No | No |
| General screening test | No | No |
| Offered at our clinic | Yes, selectively, when indicated | No |
Why neither is a screening test
EndoPAT. Its FDA clearance says it is not intended as a screening test for the general population. A review in a leading cardiology journal concluded that the use of endothelial function testing as a clinical tool in daily medicine was not yet established. The authors added that future research needed to show whether treating by the result leads to better outcomes.3
Stress testing. The US Preventive Services Task Force recommends against screening with a resting or exercise ECG to prevent cardiovascular events in adults without symptoms who are at low risk. For adults at intermediate or high risk, it found the evidence insufficient to judge the balance of benefits and harms.4 One concern it named was the potential harm of invasive tests that follow an abnormal screening result.
In plain terms: if you feel well and want to understand your risk, neither of these is the place to start.
Can a normal result on one reassure you about the other?
No. A normal stress test says that no artery is narrowed enough to starve the heart during exertion. It says nothing about how the vessel lining is working or how much plaque is present.
A normal EndoPAT says the small vessels in your hand responded well on that day. It does not rule out plaque or a blockage in a coronary artery. Readings also vary from one session to the next, so a small change between two tests may mean nothing.5
It works the other way too. An abnormal EndoPAT is not a diagnosis of heart disease, and an abnormal stress test in someone without symptoms is sometimes a false alarm.
Which one might apply to you?
- You have chest pressure, breathlessness or unusual fatigue with exertion. See your doctor or a cardiologist. A stress test or another diagnostic test may be ordered. If symptoms are severe or happening now, call 911.
- You feel well and want to know your risk. Start with the measures that have the strongest evidence: blood pressure, ApoB, Lp(a), blood sugar and, when a decision is uncertain, a calcium score.
- The basics are done and a question about vessel function remains. This is where a provider might consider EndoPAT. Erectile dysfunction is one example, because it can be an early vascular sign. See our page on erectile dysfunction.
EndoPAT, stress testing and Cardio Res-Q
EndoPAT is done in our office and used selectively, when indicated. It is an add-on that is not included in either entry assessment, and whether it applies to you is decided after your evaluation. The Comprehensive Assessment ($775) covers Dr. Varano's clinical evaluation, advanced labs and a personalized heart protection plan. The Enhanced Assessment ($999) adds a CIMT ultrasound and a coronary calcium score.
We do not perform stress tests. Cardio Res-Q is not emergency care and does not replace a cardiologist, and our team can share your results with the doctors you already see. Read Cardio Res-Q vs. a cardiologist visit to see who does what, or start on 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
Can EndoPAT replace a stress test?
No. If you have symptoms that could come from your heart, EndoPAT cannot show whether an artery is narrowed. That question needs a diagnostic test chosen by your doctor or cardiologist.
I passed a stress test. Would EndoPAT add anything?
It measures something different, so it could, but only if the result would change what you and your provider do. For most people, lab markers and a calcium score say more about long-term risk.
Does EndoPAT involve exercise or radiation?
No. You lie still while a cuff on one arm is inflated for a few minutes. There is no treadmill, no injection and no radiation. You arrive fully fasted and with no caffeine.
How much does EndoPAT cost at your clinic?
EndoPAT is an add-on. It is not included in the $775 or $999 assessment, and its price is not published. Ask our team after your evaluation.
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.
