An ejection fraction of 40% or below is the most widely recognized threshold for heart failure, but heart failure can occur at any ejection fraction, even a normal one. A normal left ventricular ejection fraction falls between about 50% and 70%, meaning the heart pumps out roughly half to two-thirds of the blood in its main pumping chamber with each beat. When that number drops, or when the heart muscle stiffens even while pumping normally, heart failure can develop.
The Four Ejection Fraction Categories
The 2022 guidelines from the American Heart Association, American College of Cardiology, and Heart Failure Society of America divide heart failure into four types based on ejection fraction:
- Reduced (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 (HFmrEF): 41% to 49%. The heart is pumping below normal but not severely so. Diagnosis also requires evidence of elevated filling pressures inside the heart.
- Preserved (HFpEF): 50% or above. The heart squeezes normally but has become stiff, so it can’t relax and fill properly between beats. Symptoms like shortness of breath and swelling still occur.
- Improved (HFimpEF): Previously 40% or below, then rises above 40% on a follow-up measurement. This category recognizes that some people respond well to treatment and recover pumping strength, though the underlying condition still needs ongoing management.
Why a Normal Ejection Fraction Doesn’t Rule Out Heart Failure
This surprises many people. Heart failure with preserved ejection fraction accounts for roughly half of all heart failure cases, and the ejection fraction reads 50% or higher. The problem isn’t squeezing; it’s filling. The heart muscle becomes stiff, so pressure builds up as blood tries to enter the chamber between beats. In one study of patients with heart failure and normal ejection fractions, 92% had abnormally high filling pressures, and every single patient showed at least one measurable abnormality in how the heart relaxed.
Because the ejection fraction looks fine on paper, this type of heart failure is harder to diagnose. Doctors typically need additional evidence, such as elevated levels of a protein the heart releases when it’s under strain (called BNP or NT-proBNP), or direct pressure measurements showing the heart isn’t filling correctly.
How Ejection Fraction Affects Survival
Lower ejection fractions carry higher risk, but the relationship isn’t as steep as you might assume. A large study tracking over 2,700 heart failure patients found clear differences across all three main categories. At one year, the all-cause mortality rate was 11% for reduced ejection fraction, 8% for mildly reduced, and 5% for preserved. At five years, those numbers climbed to 31%, 20%, and 17%.
The gap widened further for deaths specifically from cardiac causes. At ten years, cardiac mortality was 25% for the reduced group compared to 11% for mildly reduced and 8% for preserved. Interestingly, deaths from non-cardiac causes were virtually identical across all three groups at every time point, hovering around 3% at one year and 14% at ten years. This means the extra risk from a lower ejection fraction is almost entirely heart-related, which is why targeted treatment makes such a difference.
How Ejection Fraction Is Measured
The most common method is an echocardiogram, an ultrasound of the heart that takes about 30 to 60 minutes and involves no radiation. Cardiac MRI is considered the gold standard for accuracy. When researchers compared the two methods head to head, the average difference between them was less than 2 percentage points, though individual measurements could vary more widely. This variability matters most when your number sits right at a cutoff like 40% or 50%, since a small measurement difference could shift your classification.
Your ejection fraction can also change over time. It may drop during an acute illness and recover afterward, or it may improve significantly with medication and lifestyle changes. A single measurement is a snapshot, not a permanent label.
The Stages of Heart Failure
Ejection fraction describes how well the heart pumps, but doctors also classify heart failure by how far it has progressed. These stages run from A through D and don’t move backward, even if symptoms improve.
Stage A means you’re at risk due to conditions like high blood pressure, diabetes, or obesity, but you have no symptoms and no structural changes in the heart yet. Stage B, called pre-heart failure, means imaging or lab tests show something has changed in the heart’s structure or function, but you still feel fine. Stage C is where symptoms appear: shortness of breath, fatigue, swelling in the legs, or difficulty exercising. Stage D is advanced heart failure, where symptoms interfere with daily life despite treatment and often lead to repeated hospitalizations.
The distinction matters because treatment strategies differ at each stage, and catching heart failure early (at Stage A or B) gives you the best chance of slowing or preventing progression.
Right Ventricular Ejection Fraction
Most discussions of heart failure focus on the left ventricle, which pumps blood to the entire body. But the right ventricle, which sends blood to the lungs, has its own ejection fraction, and it carries independent risk. A normal right ventricular ejection fraction is above 51%. When it drops below 40%, the risk of major cardiovascular events jumps roughly threefold, with a one-year event rate of 22% compared to 7% for those above that cutoff. Right ventricular function is typically assessed with cardiac MRI rather than standard echocardiography.