What do doctors mean by “ejection fraction” in heart failure?
If you are undergoing tests for heart issues, you will likely hear your doctor mention your ‘ejection fraction’ or ‘EF’. It is a key number that helps cardiologists understand how well your heart is pumping. While the term sounds technical, the concept is straightforward: it is a measurement of the percentage of blood leaving your heart each time it contracts. Understanding this number can help you better understand your diagnosis and treatment options.
What We’ll Discuss in This Article
- The definition of ejection fraction (EF)
- How doctors measure and calculate it
- What constitutes a normal, borderline, or low score
- The difference between HFrEF and HFpEF
- Causes of a reduced ejection fraction
- Triggers that can worsen heart function
- Why this number matters for your treatment
What is ejection fraction?
Ejection fraction is a measurement, expressed as a percentage, of how much blood the left ventricle pumps out with each contraction. The left ventricle is the heart’s main pumping chamber. It fills with blood and then squeezes it out to the rest of the body. The ejection fraction tells us how efficient that squeeze is.
How it Works
It is important to note that the heart does not pump out 100% of the blood inside it with every beat. Even a healthy heart leaves some blood behind.
- Diastole (Relaxation): The ventricle relaxes and fills with blood.
- Systole (Contraction): The ventricle squeezes to pump blood out.
- The Calculation: If the ventricle holds 100ml of blood and pumps out 60ml, the ejection fraction is 60%.
Clinical Context
According to the British Heart Foundation, an echocardiogram (an ultrasound scan of the heart) is the most common way to measure this. It provides a moving picture of the heart, allowing doctors to estimate the percentage accurately.
What is a normal ejection fraction?
Many people assume that a normal score is 100%, but this is not the case. A healthy heart keeps a reserve of blood in the ventricle.
Typical Ranges
- Normal Range (50% to 75%): The heart is pumping efficiently. A reading in this range usually means the heart’s pumping function is normal.
- Borderline (41% to 49%): The pumping function is slightly below normal. This may not cause symptoms during rest but might become noticeable during exercise.
- Reduced (40% or less): The heart muscle is not pumping as well as it should. This is often the threshold for diagnosing ‘heart failure with reduced ejection fraction’.
Safety Note
A normal ejection fraction does not guarantee a perfectly healthy heart. You can still have heart failure if the muscle is stiff rather than weak (heart failure with preserved ejection fraction).
What causes a low ejection fraction?
A low ejection fraction is typically a sign that the heart muscle has been damaged or weakened. This damage prevents the ventricle from squeezing with enough force.
Primary Causes
- Coronary Heart Disease: Blocked arteries reduce oxygen supply to the muscle.
- Heart Attack: A previous heart attack leaves scar tissue. Scar tissue does not contract, so the overall pumping power drops.
- Cardiomyopathy: Genetic or acquired diseases that cause the heart muscle to become stretched, thickened, or stiff.
- Heart Valve Disease: If a valve leaks or is narrowed, the heart has to work harder, eventually weakening the muscle.
- Uncontrolled High Blood Pressure: Long-term strain can weaken the ventricle over time.
Triggers for Worsening EF
For patients who already have a reduced ejection fraction, certain factors can cause the number to drop further or trigger sudden symptoms.
- Arrhythmias: An irregular heartbeat, such as atrial fibrillation, means the heart cannot fill or pump efficiently.
- Alcohol and Drugs: Toxins can directly damage heart muscle cells.
- Chemotherapy: Certain cancer treatments can weaken the heart muscle as a side effect.
- Viral Infections: Infections like myocarditis can cause temporary or permanent inflammation of the heart muscle.
Differentiation: HFrEF vs HFpEF
Doctors use ejection fraction to classify heart failure into two main types. This distinction is vital because the treatments differ.
Heart Failure with Reduced Ejection Fraction (HFrEF)
- The Problem: Pumping failure.
- EF Score: Usually 40% or lower.
- Mechanism: The heart muscle is weak, floppy, and enlarged. It cannot squeeze hard enough.
- Treatment: Focuses on strengthening the squeeze and reducing the workload (e.g., beta-blockers, ACE inhibitors).
Heart Failure with Preserved Ejection Fraction (HFpEF)
- The Problem: Filling failure.
- EF Score: Usually 50% or higher (Normal).
- Mechanism: The heart muscle is too stiff or thick. It squeezes well, but because it is stiff, it does not fill with enough blood in the first place.
- Treatment: Focuses on managing fluid levels (diuretics) and treating underlying causes like high blood pressure.
Conclusion
Ejection fraction is a vital measurement that tells doctors how efficiently your heart is pumping blood. A normal range is generally between 50% and 75%, while anything below 40% suggests significant weakness in the heart muscle. However, it is just one piece of the puzzle; you can have heart symptoms even with a normal score if the heart is stiff. Knowing your number helps you and your medical team choose the safest and most effective therapies to support your heart health.
Emergency Guidance
If you experience severe breathlessness, chest pain, or faintness, call 999 immediately. Do not rely on your known ejection fraction numbers to judge an emergency; symptoms are the most important indicator.
FAQ Section
1. Can my ejection fraction improve?
Yes. With proper medication (like beta-blockers and ACE inhibitors) and sometimes devices like pacemakers, the heart muscle can strengthen, and the ejection fraction can increase over time.
2. Is an ejection fraction of 40% dangerous?
It indicates significant heart dysfunction, but it is a manageable condition. Many people live active lives with an EF of 40% or lower, provided they follow their treatment plan.
3. How often should I have my ejection fraction checked?
It depends on your condition. According to the NHS, doctors typically check it when you are first diagnosed and then periodically if your symptoms change or to monitor medication effectiveness.
4. Can I feel my ejection fraction dropping?
Not exactly. You cannot feel the number itself, but you will likely feel the result: increased breathlessness, fatigue, or fluid retention (swelling in the ankles).
5. Does a low ejection fraction mean I need a transplant?
Not necessarily. Most people with low EF are managed successfully with medication. Transplants are reserved for very severe cases that do not respond to other treatments.
6. Is ejection fraction the same as heart rate?
No. Heart rate is how many times the heart beats per minute. Ejection fraction is how much blood is pumped with each beat.
7. Can exercise improve my ejection fraction?
Yes. Cardiac rehabilitation and safe, regular exercise can improve overall heart efficiency and muscle function, though you should always consult your specialist before starting a new regime.
Authority Snapshot
This article was written by Dr. Rebecca Fernandez, a UK-trained physician with extensive experience in cardiology, internal medicine, and emergency care. Dr. Fernandez has managed critically ill patients and provided comprehensive care for acute and chronic conditions within the NHS framework. This guide uses standard NHS and British Heart Foundation definitions to explain ejection fraction, ensuring clear, accurate, and medically safe information.
