Fractional Flow Reserve

A fractional flow reserve assessment compares the blood flow on either side of a blockage in your coronary artery. This tells your provider how severe the narrowing (stenosis) is in your artery. If your result is less than 1, you may need medical treatment or angioplasty. Your number helps your provider choose your treatment.


What is fractional flow reserve?

Fractional flow reserve (FFR) is a minimally invasive procedure to figure out how bad the narrowing (stenosis) is in your coronary arteries. Your healthcare provider does this by checking the blood pressure and flow in your coronary arteries. Your provider compares the highest possible blood flow you can have with and without a blockage.

Providers do the fractional flow reserve test as part of a cardiac catheterization of your heart’s left side or during a coronary angiogram. The results help them decide which treatment you need.


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When would fractional flow reserve be needed?

You may need this test when your healthcare provider is deciding whether you need angioplasty and a stent in one of your coronary arteries. They carry blood containing oxygen to your heart muscle.

Providers use this cost-effective, simple test when imaging shows you have 50% to 70% diameter narrowing (stenosis). In some cases, providers may check fractional flow reserve in people with up to 90% narrowing.

You shouldn’t need this test if your narrowing is lower than 30% or higher than 70%. This is because it’s already clear that you don’t need angioplasty if have minimal stenosis, but you do if your number is high.

After you’ve had angioplasty and a stent put into your coronary artery, fractional flow reserve can help predict whether you’ll have a major heart issue.

What are the drawbacks of a fractional flow reserve assessment?

Your provider can get a false normal result if your coronary arterioles — your smallest arteries — don’t respond to the drug that increases blood flow during the fractional flow reserve procedure. The length of the narrow area affects your FFR as well.


What is iFR and FFR?

Both are tests that determine how severe the narrowing is in coronary arteries. Instant wave-free ratio (iFR) doesn’t use a drug like adenosine (Adenocard® or Adenoscan®) to widen your blood vessels for the test. FFR does.

Who performs fractional flow reserve?

A cardiologist performs a fractional flow reserve test.


Test Details

How does a fractional flow reserve test work?

Your provider uses an instrument to take blood pressure readings on both sides of a blockage inside your coronary artery. The equipment uses these readings to calculate your fractional flow reserve.

How do I prepare for the coronary fractional flow reserve assessment?

Your provider may ask you to stop taking certain medicines, especially blood thinners, several days before your test. Also, don’t eat or drink anything after midnight the night before your procedure.

Since you’re going to have anesthesia, you’ll need someone to drive you home.

What to expect on the date of the fractional flow reserve assessment

Your test will take less than an hour. However, if your provider decides to do an angioplasty and put in a stent, those will take additional time.

You also may need to allow for preparation and recovery time. Check with your provider about the total time you can expect to spend at the hospital.

What to expect during the fractional flow reserve test

Your healthcare provider will:

  1. Inject a local anesthetic into your skin.
  2. Insert a needle in your arm, neck or groin.
  3. Use the needle to thread a catheter into your artery.
  4. Advance the catheter through arteries to get to your aorta and then your coronary arteries, which come out of your aorta. Fluoroscopy (X-ray) helps your provider see where the catheter is going.
  5. Inject liquid contrast media through the catheter and into your coronary arteries to make them easier to see.
  6. Check for blockages in your coronary arteries.
  7. Use an ultrasound device on the catheter to look at your blood flow.
  8. Give you heparin and nitroglycerin (Nitronal® or Tridil®) before moving a pressure wire into the narrow area.
  9. Use the catheter’s pressure sensors to check the pressure on either side of the narrow part in your coronary artery. For an accurate measurement, they check this when blood flow is at its highest. They give you medicine (adenosine or papaverine) to increase your blood flow.
  10. Perform an angioplasty and stent placement in your coronary artery if you need it.
  11. Check your FFR again after completing the angioplasty and putting in a stent.
  12. Remove the catheter and put pressure on your access site.

What should I expect after the fractional flow reserve procedure?

People don’t have a lot of discomforts and rarely have complications from an FFR test. Most people can go home a few hours after their FFR procedure. However, if you have angioplasty and a stent, you may need to stay overnight in the hospital.

What are the side effects of a coronary fractional flow reserve procedure?

You may feel chest pain and/or shortness of breath about a minute after your healthcare provider gives you adenosine through your IV or directly into your coronary artery. This reaction is normal and helps your provider know that it’s time to take the readings because your blood flow is at its peak.

Papaverine can cause an abnormal heart rhythm in 1% of cases. Normally, this only lasts a short time.

Because you get a fractional flow reserve procedure during cardiac catheterization, you accept the risks of that procedure as well.

Results and Follow-Up

How do you calculate fractional flow reserve?

To make a fractional flow reserve calculation, divide the pressure on the other side (distal) of the blockage by the pressure closer (proximal) to the blockage. Your provider collects these fractional flow reserve measurements during cardiac catheterization.

What type of results do you get and what do the results mean?

You should get a number. A normal result ranges from 0.94 to 1. Any number below that means you need some type of treatment because your blood flow is less than what it should be. For example, if your FFR is 0.75, your narrow section of the coronary artery is causing a 25% decrease in pressure.

Low blood supply/flow
Lower blood supply/flow ("grey zone")
0.75 to 0.80
Angioplasty and stent or medicine
Lowest blood supply/flow
Angioplasty and stent

If your fractional flow reserve shows that your coronary artery blockage isn’t bad, you don’t need angioplasty and a stent. You can take medicine instead.

When should I know the results of the fractional flow reserve assessment?

When your healthcare provider takes your pressure measurements, they’ll see your pressure numbers and FFR on their equipment console. They may tell you what your FFR is during or after the procedure.

When should I call my doctor?

After your fractional flow reserve procedure, let your provider know if you have:

  • Chest pain.
  • Shortness of breath.
  • Fever.
  • Pain at your access site.
  • Dizziness.
  • An abnormal heart rhythm or palpitations.

A note from Cleveland Clinic

A fractional flow reserve assessment can help your provider decide which treatment is best for your coronary artery disease. They’ll make sure you’re as comfortable as possible during the test. Ask questions about the procedure if there’s anything you don’t understand. It can be helpful to prepare yourself mentally in case you need an angioplasty and stent right after your provider calculates your fractional flow reserve.

Medically Reviewed

Last reviewed on 07/18/2022.

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