Ejection fraction is measured through imaging tests that show your heart pumping in real time. The most common method is an echocardiogram, a painless ultrasound that takes about 30 to 60 minutes. Other options include cardiac MRI and nuclear scans, though these are typically reserved for situations where more precision is needed or an echocardiogram isn’t sufficient.
Echocardiogram: The Standard Test
An echocardiogram is the first-line test for measuring ejection fraction. It uses sound waves to create a moving image of your heart, letting a technician see how much blood the left ventricle pushes out with each beat. The American Society of Echocardiography recommends a technique called the biplane method of disks, where the technician traces the inner border of the heart chamber from two different angles. Software divides the chamber into roughly 20 slices, calculates the volume at its fullest and emptiest points, and determines what percentage of blood was ejected.
The actual formula is straightforward: the volume of blood pumped out divided by the total volume when the chamber is full. That percentage is your ejection fraction.
For a standard transthoracic echocardiogram (the kind done from outside the chest), you don’t need to fast or do any special preparation. You’ll remove clothing from the waist up, and women are given a gown. A technician applies gel to your chest and moves a small probe across it. Some echocardiograms require a saline solution or contrast dye injected into a vein to improve the image quality, but many don’t. There’s no radiation, no pain, and no recovery time.
A transesophageal echocardiogram, where the probe goes down the throat for a closer view, requires fasting for about 8 hours beforehand. This version is less common for routine ejection fraction checks.
Cardiac MRI: The Most Accurate Option
Cardiac MRI is considered the gold standard for measuring ejection fraction because it produces highly detailed 3D images of the heart without relying on geometric assumptions about the chamber’s shape. Where an echocardiogram estimates volume from two-dimensional slices, an MRI captures the full structure.
You’ll lie inside a scanner for 45 to 90 minutes. A contrast dye may be injected into a vein in your arm to highlight the heart and blood vessels, though not all cardiac MRI studies require it. If you’re uncomfortable in enclosed spaces, your doctor can prescribe something to help you relax. There’s no radiation exposure.
Cardiac MRI is often used when echocardiogram images are poor quality, when precise tracking of ejection fraction changes matters (such as during cancer treatment that can damage the heart), or when a diagnosis hinges on getting the most accurate number possible.
MUGA Scan: Common in Cancer Care
A MUGA scan (multiple gated acquisition scan) has been used since the 1970s to track ejection fraction, particularly in cancer patients receiving chemotherapy drugs that can weaken the heart. A small amount of radioactive tracer is injected into a vein, and a gamma camera records how the heart contracts.
While MUGA results are close to cardiac MRI on average (off by only about 1.5 percentage points), individual readings can vary widely. A study comparing MUGA to cardiac MRI in cancer patients, published in the Journal of Cardiovascular Magnetic Resonance, found that the range of disagreement between the two methods spanned roughly 36 percentage points. At a threshold of 50%, MUGA misclassified 35% of patients compared to the MRI reference. That level of imprecision can matter when treatment decisions depend on whether ejection fraction has dropped below a specific cutoff. MUGA also involves ionizing radiation, which is a concern for patients who need repeated scans over time.
Cardiac Catheterization: Rarely Used for EF Alone
Ejection fraction can also be measured during a cardiac catheterization through a procedure called left ventriculography. A catheter is threaded into the heart, contrast dye is injected directly into the left ventricle, and X-ray imaging captures the chamber contracting. The procedure itself takes about five minutes.
This method carries real risks: adverse reactions to contrast dye (especially for people with kidney problems or diabetes), increased radiation exposure, abnormal heart rhythms, and a small chance of dislodging a blood clot and causing a stroke. Because noninvasive imaging can measure ejection fraction reliably, ventriculography is not done solely for that purpose. It’s typically performed only when a patient is already undergoing catheterization for another reason, such as evaluating coronary artery disease.
Can You Check It at Home?
No consumer device currently measures ejection fraction. Smartwatches and home monitors can track heart rate, rhythm, and even detect atrial fibrillation, but ejection fraction requires imaging the heart’s chambers in motion and calculating volumes. That level of detail is beyond what any wearable or at-home device can provide.
Some implantable devices, like pressure sensors placed in the pulmonary artery, allow remote monitoring of heart failure by tracking pressure changes. These can flag worsening heart failure, but they measure artery pressure, not ejection fraction itself. Getting your ejection fraction checked still requires a visit to a clinic or hospital with imaging equipment.
What the Numbers Mean
Ejection fraction is expressed as a percentage. Normal ranges differ slightly between men and women:
- Normal: 52% to 72% for men, 54% to 74% for women
- Mildly reduced: 41% to 51% for men, 41% to 53% for women
- Moderately reduced: 30% to 40% for both
- Severely reduced: below 30% for both
These ranges matter because heart failure is classified based on where your number falls. An ejection fraction of 40% or below is categorized as heart failure with reduced ejection fraction, meaning the heart muscle is too weak to pump effectively. An ejection fraction of 50% or above can still be associated with heart failure if the heart muscle has become too stiff to fill properly, a condition called heart failure with preserved ejection fraction. The 41% to 49% range sits in the middle and is sometimes called heart failure with mildly reduced ejection fraction.
A single ejection fraction reading is a snapshot. The number can change over time with treatment, lifestyle changes, or disease progression. That’s why doctors often order repeat echocardiograms every few months to a year, depending on the situation, to track the trend rather than relying on any one measurement.