Heart failure doesn’t begin at a single ejection fraction number. A normal left ventricular ejection fraction falls between 50% and 70%, meaning your heart pumps out roughly half to two-thirds of its blood with each beat. Heart failure can be diagnosed at any ejection fraction, even a normal one, as long as symptoms and structural heart changes are present. That said, specific cutoffs determine which type of heart failure you have, and those categories shape treatment decisions.
The Three Ejection Fraction Categories
Cardiologists classify heart failure into three groups based on ejection fraction, each with a distinct name and percentage range:
- Reduced ejection fraction (HFrEF): 40% or below. The heart muscle is weakened and can’t pump enough blood forward. This is what most people picture when they think of heart failure.
- Mildly reduced ejection fraction (HFmrEF): 41% to 49%. The heart’s pumping ability is below normal but not severely impaired. This category was previously called “mid-range” and sits in a gray zone between the other two types.
- Preserved ejection fraction (HFpEF): 50% or higher. The heart squeezes normally, but it’s stiff and doesn’t relax properly between beats, so it can’t fill with enough blood. Despite a normal-looking percentage, the heart still fails to meet the body’s demands.
The preserved category is the one that surprises most people. You can have genuine heart failure with an ejection fraction of 55% or even 60%. European cardiology guidelines define HFpEF as symptoms of heart failure, an ejection fraction of 50% or above, plus objective evidence of structural or functional heart abnormalities. Diagnosing it is more complex than the reduced type, and there’s still debate among specialists about the exact cutoff to use.
Why the Number Alone Doesn’t Tell the Whole Story
Symptoms of heart failure look similar regardless of where your ejection fraction lands. Shortness of breath, fatigue, swelling in the legs, and difficulty with physical activity occur across all three categories. A person with an ejection fraction of 30% might feel the same day to day as someone at 50% who has a stiff, poorly relaxing heart.
Doctors use a separate system called the NYHA classification to describe how heart failure actually affects your life. It runs from Class I, where ordinary activity causes no symptoms, through Class IV, where symptoms appear even at rest. Your ejection fraction and your functional class don’t always line up neatly. Someone with a low ejection fraction on effective treatment may feel fine during daily activities, while someone with a preserved ejection fraction and poor fitness may struggle with a flight of stairs.
How Ejection Fraction Affects Outlook
Lower ejection fractions do carry higher risk overall. In a large meta-analysis, patients with mildly reduced ejection fraction (41% to 49%) had a 16% lower risk of dying at one year compared to those with reduced ejection fraction (40% or below). That gap held at two and three years. By five and ten years, however, the difference between the two groups was no longer statistically significant, suggesting that long-term risk eventually converges.
Patients in the mildly reduced group had roughly the same mortality risk as those with preserved ejection fraction at every time point measured. So while a lower number signals more immediate danger, the preserved category is not harmless. It carries its own long-term burden.
When Ejection Fraction Triggers Device Decisions
Certain treatment thresholds are tied directly to your ejection fraction. The most consequential is 35%: current guidelines give the strongest recommendation for an implantable cardioverter-defibrillator (ICD) in patients whose ejection fraction is 35% or below, who have mild to moderate symptoms despite optimal medication, and who are expected to live at least another year. For people who have had a heart attack, the threshold drops even lower. An ICD is recommended when ejection fraction falls below 30%, even without symptoms.
These thresholds matter because sudden cardiac death risk rises as ejection fraction drops. The device monitors heart rhythm continuously and delivers a shock if a life-threatening arrhythmia occurs. Knowing your exact number, not just “low” or “borderline,” can determine whether you’re a candidate.
Ejection Fraction Can Improve
A diagnosis of reduced ejection fraction isn’t necessarily permanent. With proper treatment, some people experience meaningful recovery. The formal definition of “improved ejection fraction” requires three things: a baseline ejection fraction of 40% or below, an increase of at least 10 percentage points, and a follow-up measurement above 40%. This improvement typically occurs within one month to one year after starting treatment.
Not everyone improves, and the degree of recovery varies. But knowing that your ejection fraction can shift upward is important context. It’s one reason cardiologists repeat the measurement periodically rather than relying on a single test. If your number does climb past 40% with a 10-point gain, your risk profile changes, and your treatment plan may be adjusted accordingly.
How Ejection Fraction Is Measured
The most common way to measure ejection fraction is an echocardiogram, an ultrasound of the heart that takes about 30 to 60 minutes and involves no radiation. A technician places a probe on your chest, and the images show how much blood the left ventricle ejects with each contraction. Cardiac MRI provides a more precise measurement and is sometimes used when echocardiogram images are unclear or when a more detailed look at heart muscle damage is needed. Nuclear stress tests can also estimate ejection fraction by tracking a small amount of radioactive tracer through the heart.
Results can vary by a few percentage points between tests and between methods, which is why trends over time matter more than any single reading. If your echocardiogram shows an ejection fraction of 42% on one visit and 38% on another, the clinical picture and your symptoms help determine which category best fits your situation.