Fractional Flow Reserve (FFR): Deciding Whether You Need a Stent
Updated: 2 days ago
Written and medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: November 2026 · How we review
Quick Answer
Fractional flow reserve (FFR) is a test done during a coronary angiogram that measures how much a narrowed heart artery limits blood flow. A normal FFR is 0.94 to 1. An FFR of 0.80 or higher usually means the narrowing can be treated with medicine, while lower values usually mean a stent will help.
What the research says
FFR-guided stenting leads to better outcomes: in 1,005 people with blockages in several heart arteries, guiding stents by FFR lowered major heart events at 1 year from 18.3% to 13.2% and reduced stents per patient from 2.7 to 1.9 (Tonino PA et al., N Engl J Med, 2009) [2]
Stents help when FFR is low: in 888 people with stable coronary disease and an FFR showing limited flow, FFR-guided stenting cut the main combined outcome to 4.3% vs. 12.7% with medicine alone, mostly by reducing urgent procedures (De Bruyne B et al., N Engl J Med, 2012) [3]
Key takeaways
FFR measures whether a heart artery narrowing truly limits blood flow.
It's done during a coronary angiogram with a pressure wire.
An FFR of 0.80 or higher usually means medicine is enough.
An FFR of 0.80 or lower usually means a stent may help.
FFR-guided care leads to fewer heart events and fewer unneeded stents.
What is fractional flow reserve?
An angiogram shows how narrow an artery looks, but not always whether it limits blood flow enough to matter. FFR answers that question. It's the ratio of the blood pressure beyond the narrowing to the pressure before it, measured when blood flow is at its maximum. A similar test, the instant wave-free ratio (iFR), doesn't need adenosine. FFR is related to coronary flow reserve, which measures total flow increase. Sources: [1]
Why it's done
FFR helps match treatment to how much a blockage matters.
Deciding whether a stent is needed for a narrowing of about 50% to 70%, and sometimes up to 90%.
Choosing which of several blockages to treat.
Avoiding stents for narrowings that don't limit blood flow.
Checking results after stent placement. Sources: [1]
FFR usually isn't needed when narrowing is below 30% or clearly above 70%. Sources: [1]
How to prepare
Stop certain medicines, especially blood thinners, as directed, sometimes several days before.
Don't eat or drink after midnight the night before.
Bring a list of your medicines and allergies.
Arrange for someone to drive you home. Sources: [1]
What happens during the test
FFR adds less than an hour to the angiogram.
The skin is numbed, and a catheter is threaded through an artery in your wrist, arm, neck or groin to the heart.
Contrast dye shows the narrowed area.
A thin pressure wire is passed across the narrowing.
Adenosine or papaverine is given to increase blood flow.
Pressures before and after the narrowing are compared. If needed, angioplasty and a stent are placed and FFR is rechecked. Sources: [1]
Risks
About a minute after adenosine, many people feel brief chest pain or shortness of breath, which is expected. Papaverine causes an abnormal heart rhythm in about 1% of cases, usually briefly. The usual risks of cardiac catheterization, such as bleeding at the access site, also apply. Most people go home a few hours later; those who get a stent may stay overnight. Sources: [1]
What the results mean
Your cardiologist uses FFR to choose treatment.
FFR value | What it means | Usual treatment |
0.94 to 1 | Normal flow | No treatment for that artery |
0.80 or higher | Narrowing doesn't significantly limit flow | Medicine |
0.75 to 0.80 | Usually significant | Medicine or stent, case by case |
Below 0.75 | Narrowing limits flow | Angioplasty and stent |
Results are often shared during or right after the procedure. Sources: [1, 2, 3]
Conclusion
FFR helps your cardiologist decide which heart artery narrowings truly need a stent. This measurement-based approach leads to better outcomes and fewer unnecessary procedures than relying on the angiogram picture alone.
Keep learning: read about the coronary angiogram and intravascular ultrasound (IVUS).
Frequently asked questions
What is fractional flow reserve?
A measurement of how much a narrowed heart artery limits blood flow.
How is FFR measured?
With a pressure wire during a coronary angiogram.
What is a normal FFR?
0.94 to 1.
What FFR needs a stent?
Usually 0.80 or lower, based on current guidelines.
What does adenosine feel like?
Many people feel brief chest pain or shortness of breath.
How long does FFR take?
Less than an hour, not counting any stent placement.
Will I be awake?
Yes, with local numbing and sometimes a sedative.
What is iFR?
A similar test that doesn't need adenosine.
Can I go home the same day?
Usually yes, unless you get a stent.
Why is FFR useful?
It helps avoid unnecessary stents and target the right blockages.
Related Reading
Coronary Angiogram: Why It's Done, What to Expect and Recovery the X-ray test during which FFR is done.
Coronary Flow Reserve (CFR): What It Measures and Normal Values a related measure of heart blood flow.
Intravascular Ultrasound (IVUS): Seeing Inside Arteries to Guide Stents another test used to guide stents.
Coronary Revascularization: PCI vs. Bypass Surgery, Risks and Recovery stents and bypass surgery.
Cardiac Catheterization (Heart Cath): Why It's Done, Procedure, Risks and Recovery the procedure used to reach the heart arteries.
References
Cleveland Clinic. Fractional Flow Reserve (FFR): Definition and Calculation. Cleveland Clinic. Last updated July 18, 2022. https://my.clevelandclinic.org/health/diagnostics/23556-fractional-flow-reserve
Tonino PA, De Bruyne B, Pijls NH, et al. Fractional flow reserve versus angiography for guiding percutaneous coronary intervention. N Engl J Med. 2009;360(3):213-224. PMID 19144937. https://doi.org/10.1056/NEJMoa0807611
De Bruyne B, Pijls NH, Kalesan B, et al. Fractional flow reserve-guided PCI versus medical therapy in stable coronary disease. N Engl J Med. 2012;367(11):991-1001. PMID 22924638. https://doi.org/10.1056/NEJMoa1205361
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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