A low ejection fraction means your heart is pumping out less blood with each beat than it should. A normal ejection fraction falls between 50% and 70%, meaning your heart pushes out more than half of the blood it fills with. When that number drops below 40%, it’s classified as reduced, and it signals that the heart muscle has weakened enough to affect how well your body receives oxygen and nutrients.
What Ejection Fraction Actually Measures
Every time your heart beats, the left ventricle fills with blood and then squeezes to push that blood out to the rest of your body. It never empties completely. Ejection fraction is simply the percentage of blood that gets pumped out with each squeeze compared to the total amount the chamber held when full. If your ventricle held 100 milliliters of blood and pumped out 60 milliliters, your ejection fraction would be 60%.
Doctors break ejection fraction into three ranges that determine how heart failure is classified and treated:
- Normal (50% or higher): The heart is squeezing with adequate force. Some people develop heart failure even with a preserved ejection fraction, usually because the heart has become stiff and doesn’t fill properly.
- Mildly reduced (36% to 49%): The heart’s pumping ability is below normal but not severely impaired. This range often warrants close monitoring and may need treatment.
- Reduced (35% or below): The heart is significantly weakened. This is the threshold that triggers the most aggressive treatment strategies, including consideration for implanted devices.
How It’s Measured
The most common way to measure ejection fraction is with an echocardiogram, an ultrasound of the heart. A technician places a probe on your chest, and sound waves create a moving image of your heart chambers in real time. The standard technique involves tracing the outline of the left ventricle at its fullest and emptiest points to calculate the percentage. This method is quick and painless but somewhat operator-dependent, meaning results can vary slightly depending on who performs and reads the test.
When more precision is needed, cardiac MRI serves as the gold standard. It provides highly detailed images and more consistent measurements. Newer artificial intelligence tools applied to echocardiograms are closing this accuracy gap, showing strong agreement with cardiac MRI results in recent studies.
What Causes Ejection Fraction to Drop
The most common cause is coronary artery disease. When arteries supplying the heart muscle become blocked, parts of the muscle can be damaged or starved of oxygen, leaving them too weak to contract effectively. A heart attack is the most dramatic version of this, but chronic reduced blood flow can quietly erode pumping strength over time.
Other conditions that weaken the heart muscle include severe or long-standing high blood pressure (which forces the heart to work harder until it eventually tires), heart valve disease (which disrupts the normal flow of blood through the chambers), and myocarditis (inflammation of the heart muscle, often triggered by a viral infection). Less common causes include an overactive thyroid, prolonged periods of very fast heart rates, alcohol-related damage, and certain chemotherapy drugs.
Symptoms of a Weakened Heart
When ejection fraction drops, the body doesn’t receive enough blood to meet its demands. The earliest sign for many people is unusual fatigue or feeling winded during activities that used to feel easy, like climbing stairs or carrying groceries. As the heart weakens further, fluid starts to back up in the body because the heart can’t move blood forward efficiently.
That backup produces a recognizable pattern of symptoms: swelling in the legs, ankles, and feet; a persistent cough (sometimes producing pink-tinged mucus); wheezing; abdominal bloating from fluid accumulation; and a rapid or irregular heartbeat as the heart tries to compensate. Some people notice they can’t lie flat without feeling short of breath, or they wake up gasping at night. These symptoms tend to develop gradually, which is why some people don’t recognize how much their capacity has declined until the condition is fairly advanced.
How Low Ejection Fraction Is Treated
Treatment for a reduced ejection fraction has improved dramatically over the past decade. Current guidelines call for starting four categories of medication as early and quickly as possible, because the combined effect of all four working together significantly extends survival and reduces hospitalizations. These four pillars each target a different part of the cycle that worsens heart failure:
- Beta-blockers slow the heart rate and reduce the demand on the weakened muscle, giving it more time to fill and pump efficiently.
- ARNIs (a combination blood pressure drug) relax blood vessels and reduce the hormonal stress signals that cause the heart to remodel and weaken further.
- Mineralocorticoid antagonists block a hormone that promotes fluid retention and scarring in the heart muscle.
- SGLT2 inhibitors (originally developed for diabetes) reduce fluid overload and have shown clear benefits for heart failure regardless of whether someone has diabetes.
Each medication typically starts at a low dose and gets increased over weeks to months toward a target dose. The adjustment period requires regular check-ins to monitor blood pressure, kidney function, and how you’re tolerating the medications.
Devices and Procedures
When ejection fraction falls to 35% or below, the risk of dangerous heart rhythm problems increases substantially. At this threshold, an implantable cardioverter-defibrillator (ICD) may be recommended. This small device, placed under the skin near the collarbone, continuously monitors heart rhythm and delivers a corrective shock if it detects a life-threatening irregular beat.
Some people also benefit from cardiac resynchronization therapy, which uses a specialized pacemaker to coordinate the timing of the heart’s contractions so both sides pump together more effectively. In cases where blocked coronary arteries are contributing to the problem, restoring blood flow through stenting or bypass surgery can sometimes recover function in heart muscle that was “hibernating” from lack of oxygen, though identifying patients who will benefit from this approach remains challenging.
Lifestyle Changes That Matter
Sodium is a major driver of fluid retention, which directly worsens symptoms. The Heart Failure Society of America recommends keeping sodium intake between 2,000 and 3,000 milligrams per day for people with heart failure, and below 2,000 milligrams for moderate to severe cases. For context, a single fast-food meal can easily contain 1,500 milligrams or more. Fluid intake also matters: limiting total fluids to around 50 ounces per day (including water-rich foods like fruit) helps prevent the fluid overload that leads to swelling and shortness of breath.
Regular physical activity, even at modest levels, improves exercise tolerance and quality of life. Structured cardiac rehabilitation programs are particularly valuable because they provide supervised, individually tailored exercise in a monitored setting. Daily weight monitoring is one of the simplest and most effective self-management tools. A sudden gain of two or more pounds overnight, or three to five pounds in a week, typically signals fluid buildup and is a reason to contact your care team promptly.
Can Ejection Fraction Improve?
In some cases, yes. Certain causes of low ejection fraction are partially or fully reversible. Takotsubo cardiomyopathy (sometimes called “broken heart syndrome,” triggered by severe emotional or physical stress) often resolves on its own within weeks. Cardiomyopathy caused by prolonged rapid heart rates can improve dramatically once the rhythm is controlled. Thyroid-related heart weakness typically responds to treating the underlying thyroid condition.
Even in cases of permanent heart muscle damage, like after a heart attack, the four-pillar medication approach frequently leads to measurable improvements in ejection fraction over months. Some patients see their numbers rise from the 20s or 30s back into a near-normal range. This recovery depends on many factors, including how quickly treatment begins, how much of the muscle is scarred versus stunned, and how consistently medications are taken at their target doses. The possibility of improvement is one reason guidelines emphasize starting all four medication classes as early as possible.