Heart Ejection Fraction Explained: What’s Safe and What’s Not

Think of your heart as a muscular pump. With every heartbeat, it contracts to push blood out to your body. Ejection fraction (EF) is a measurement of the percentage of blood that the left ventricle (the heart’s main pumping chamber) pumps out with each contraction. ^[1]

For example, if your left ventricle holds 100 milliliters of blood before a beat and pumps out 60 milliliters, your ejection fraction is 60%. It’s a simple but powerful indicator of how well your heart is working. A high EF means your heart is pumping a lot of blood with each beat, while a low EF means it’s not pumping as efficiently.

Ejection fraction cannot be measured with a simple blood pressure check. It requires specialized imaging tests that allow doctors to see the heart’s function in real time.

• Echocardiogram (Echo): This is the most common method for measuring EF. An echo uses sound waves to create a detailed, real-time image of your heart. It allows a cardiologist to see the heart chambers and valves and to calculate the percentage of blood pumped out with each beat.^[2]
• Cardiac MRI: A cardiac MRI is considered the gold standard for measuring EF. It provides the most precise and detailed images of the heart’s structure and function, allowing for a highly accurate EF measurement.
• Nuclear Stress Test: This test involves injecting a small amount of a radioactive substance into the bloodstream. It allows doctors to see how blood flows through the heart and can be used to calculate the EF both at rest and during exercise.
• Cardiac Catheterization: While more invasive, this procedure can also be used to measure EF by directly injecting a dye into the heart chambers.

Your ejection fraction number is a critical piece of information. Here’s a breakdown of what the different ranges mean for your health:

A normal ejection fraction is typically in the range of 55% to 70%. This means your heart is functioning efficiently and pumping a healthy volume of blood to your body with each beat.^[14] A normal EF indicates a strong and healthy heart muscle.

An EF in this range is considered borderline. It’s not necessarily a sign of a serious problem but may be an early indicator of a potential issue. A doctor may recommend lifestyle changes and regular monitoring to ensure your heart health doesn’t decline.

An EF below 50% is considered low and is a key indicator of heart failure with reduced ejection fraction (HFrEF).^[16] A low EF means your heart muscle has become weakened or stretched, making it less efficient at pumping blood to meet your body’s needs.^[17] This range is often broken down into three categories:

• Mildly Reduced: 40% to 49%
• Moderately Reduced: 35% to 39%
• Severely Reduced: Below 35%^[4]

A severely reduced EF indicates a significant risk for the symptoms and complications of heart failure.

While it might sound good to have a very high EF, a number above 70% can sometimes be a sign of an underlying heart condition. For example, in Hypertrophic Cardiomyopathy (HCM), the heart muscle becomes abnormally thick. While it may pump very forcefully, the chamber has less space to fill with blood, which can lead to complications. A high EF is not always a sign of a problem, but a doctor will investigate to ensure it is not caused by a pathological condition.

A low ejection fraction is a hallmark of heart failure, a chronic condition where the heart can’t pump enough blood to meet the body’s needs. The primary risks of a low EF are:

• Heart Failure Symptoms: As the heart’s pumping power diminishes, blood can back up in the lungs and other parts of the body, leading to symptoms like shortness of breath, especially with activity or when lying down. You may also experience fatigue, swelling (edema) in the legs and ankles, and a rapid or irregular heartbeat. ^[6]
• Increased Risk of Arrhythmias: A weakened heart muscle can be more susceptible to electrical problems, leading to irregular heartbeats (arrhythmias). These can range from a fluttering sensation to dangerous rhythms that increase the risk of sudden cardiac arrest. ^[7]
• Organ Damage: In severe cases, a consistently low EF can lead to reduced blood flow to vital organs like the kidneys and brain, potentially causing damage over time.

The good news is that a low ejection fraction is often treatable, and in many cases, it can be improved with the right interventions. The goal of treatment is to address the underlying cause, reduce symptoms, and increase the heart’s pumping efficiency.

• Lifestyle Changes: These are the foundation of heart health. Adopting a heart-healthy diet (low in sodium and saturated fat), getting regular exercise (as approved by your doctor), and quitting smoking are all crucial steps. Reducing alcohol consumption can also have a positive impact on heart function.^[8]
• Medications: Your doctor may prescribe a variety of medications to help your heart pump more efficiently and reduce its workload. These often include:
  • ACE inhibitors or ARBs: To help relax blood vessels and lower blood pressure.
  • Beta-blockers: To slow the heart rate and reduce the heart’s oxygen demands.
  • Diuretics: To help the body get rid of excess fluid and reduce swelling.
• Medical Devices: In severe cases, medical devices may be needed. An implantable cardioverter-defibrillator (ICD) can be implanted to shock the heart back into a normal rhythm if a dangerous arrhythmia occurs. A pacemaker or a cardiac resynchronization therapy (CRT) device may also be used to help the heart chambers pump in better coordination.^[10]