Hemodynamic Test: Checking Heart Output and Circulation for Fainting
Updated: 2 days ago
Written and medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: November 2026 · How we review
Quick Answer
A hemodynamic test checks how well the heart pumps and how blood moves through the body, most often to find the cause of fainting (syncope) or a circulation problem. It combines EKG monitoring, blood pressure checks, an echocardiogram and nuclear imaging. Plan for about three hours. It isn't done during pregnancy or breastfeeding.
What the research says
Positional testing finds the cause of fainting faster: in older adults with unexplained fainting, starting with a head-up tilt test led to a diagnosis in 63% within a year, compared with 29% when doctors first implanted a heart monitor, and diagnosis came after a median of 1 day versus 97 days (Rabajoli A et al., Intern Emerg Med, 2026) [2]
Heart output when upright matters: a study of people with vasovagal syncope, postural tachycardia syndrome and inappropriate sinus tachycardia found that an excessively fast upright heart rate reduced cardiac output in all three conditions (Stewart JM et al., Circ Arrhythm Electrophysiol, 2020) [3]
Key takeaways
Checks heart pumping and blood flow, often to find the cause of fainting.
Combines EKG, blood pressure, echocardiogram and nuclear imaging.
Takes about three hours.
Fast for four hours and avoid all caffeine beforehand.
Low radiation; results in about 10–14 days.
Why is it done?
The test is mainly used to find the cause of fainting (vasovagal syncope and other types) or a circulation disorder, and to guide treatment. Fainting can happen when blood flow to the brain drops briefly, when blood pressure or heart rate suddenly falls, or when blood volume shifts, as in orthostatic hypotension. Many people who faint have an underlying heart, nervous system or brain blood flow condition. Sources: [1]
Related tests include the tilt table test. Sources: [1, 2]
What does the test include?
The test takes about three hours.
EKG monitoring: electrodes record your heart rhythm and rate.
Blood pressure monitoring: an arm cuff checks pressure at intervals.
Hemodynamic echo: an echocardiogram of about 20 minutes after 20 minutes of rest measures cardiac output, and it's measured again during the test.
Nuclear imaging: a gamma camera detects a radioactive tracer given through an IV, with up to three sets of images, two lying flat and one sitting. Sources: [1]
How do I prepare?
Avoid even decaf products on test day.
Don't eat for four hours beforehand, including gum and candy; you can take medicines with a sip of water.
Avoid all caffeine on test day, including decaf and caffeine-free products.
Avoid strong water pills (diuretics) and laxatives, and ask whether your medicines contain caffeine. Don't stop medicines without asking your provider.
A pregnancy test may be needed; the test isn't done during pregnancy or breastfeeding.
People with diabetes can ask for an afternoon appointment to allow a light breakfast.
Bring your medical records, medicine list and allergy list. Sources: [1]
What happens during the test?
You lie on your back, an IV is placed and the tracer is injected before each image set. The camera is positioned over your chest and may rotate around you. You stay awake and as still as possible. Tell the team how you feel; some people feel light-headed, nauseated or notice palpitations, and a brief chill, metallic taste or odd smell can occur when the tracer goes in. Sources: [1]
After the test
You'll stay until any symptoms settle, and having a driver is a good idea if symptoms were strong. Drink extra fluids to help flush the tracer out in your urine. You'll get a card to carry for one week, because the tracer can trigger airport security alarms. Sources: [1]
Risks
Bruising, redness or swelling at the IV site is common. The tracer isn't a dye and doesn't cause allergic reactions. Radiation exposure is very low, about the same as a chest X-ray. Sources: [1]
Understanding your results
Results guide treatment for fainting and circulation problems.
Results usually take 10–14 days. The report says whether results are normal or abnormal and may identify abnormal heart rhythms, blood pressure changes, coronary artery disease, reduced blood flow (ischemia) or heart muscle damage (infarction). Your care plan may include new medicines, referrals or more tests. Learn more about hemodynamics. Sources: [1, 3]
Conclusion
A hemodynamic test brings together several measurements to show how your heart and circulation respond to position changes. It's a helpful tool for uncovering why someone faints and choosing the right treatment.
Keep learning: read about vasovagal syncope and the tilt table test.
Frequently asked questions
What is a hemodynamic test?
A test of how well your heart pumps and blood circulates.
Why is it done?
Mostly to find the cause of fainting or a circulation problem.
How long does it take?
About three hours.
Do I need to fast?
Yes, for four hours beforehand.
Can I have coffee?
No. Avoid all caffeine, including decaf.
Does it use radiation?
Yes, a very low dose, about the same as a chest X-ray.
Is the tracer a dye?
No. It doesn't cause allergic reactions.
Can I do it while pregnant?
No. It isn't done during pregnancy or breastfeeding.
Why do I need a card afterward?
The tracer can trigger airport security alarms for about a week.
When will I get results?
Usually in 10–14 days.
Related Reading
Understanding Hemodynamics: The Mechanics of Blood Flow how blood flow works.
Cardiac Output: What It Is, Normal Range, How It's Measured and What Affects It how much blood your heart pumps.
Vasovagal Syncope: Why You Faint and What to Do About It the most common cause of fainting.
Tilt Table Test: How It Works, What to Expect and What Results Mean another test for fainting.
Echocardiogram: Types, What to Expect, Results and Risks the heart ultrasound used during testing.
References
Cleveland Clinic. Hemodynamic Monitoring. Cleveland Clinic. Last updated August 10, 2022. https://my.clevelandclinic.org/health/diagnostics/17094-hemodynamic-test
Rabajoli A, Chew D, Szaszkiewicz J, et al. Tilt testing or implantable cardiac monitoring in the diagnosis of unexplained syncope. Intern Emerg Med. 2026;21(6):2231-2239. PMID 41028594. https://doi.org/10.1007/s11739-025-04128-6
Stewart JM, Medow MS, Visintainer P, et al. When sinus tachycardia becomes too much: negative effects of excessive upright tachycardia on cardiac output in vasovagal syncope, postural tachycardia syndrome, and inappropriate sinus tachycardia. Circ Arrhythm Electrophysiol. 2020;13(2):e007744. PMID 31941353. https://doi.org/10.1161/CIRCEP.119.007744
Medical disclaimer
This article is for general education only and does not replace advice from a qualified healthcare professional. Talk to your doctor about your own diagnosis and treatment, and seek emergency care right away for severe or sudden symptoms.
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