The heart functions as a muscular pump, circulating blood throughout the body to deliver oxygen and nutrients. Ejection fraction measures how effectively the heart pumps blood with each beat, providing insight into its efficiency.
Understanding Ejection Fraction
Ejection fraction indicates the percentage of blood pumped out of a ventricle with each heartbeat. This value reflects the heart’s pumping efficiency, particularly of the left ventricle, the heart’s main pumping chamber responsible for sending oxygen-rich blood to the rest of the body. Imagine the left ventricle as a balloon that fills with blood. When the heart contracts, it squeezes out a portion of that blood, but it never completely empties. The ejection fraction represents the percentage of blood ejected from the filled ventricle with each squeeze. This measurement is calculated by dividing the volume of blood pumped out per beat (stroke volume) by the total volume of blood in the ventricle at the end of its filling phase (end-diastolic volume), then multiplying by 100 to get a percentage.
Interpreting Ejection Fraction Values
Interpreting ejection fraction values helps medical professionals assess heart function. A normal left ventricular ejection fraction (LVEF) typically ranges from 50% to 70%, indicating the heart is pumping adequately. Values between 41% and 49% are considered mildly reduced, suggesting a slight decrease in pumping efficiency.
When the LVEF falls to 40% or less, it is generally considered a reduced ejection fraction and can be a sign of systolic heart failure. In this condition, the heart muscle’s ability to contract forcefully and pump blood effectively is diminished. Conversely, some individuals may have a preserved ejection fraction, meaning their LVEF is 50% or higher, yet still experience symptoms of heart failure. This can occur when the heart muscle becomes stiff and struggles to fill with enough blood, even though it can pump out a normal percentage of what it does hold.
A very high ejection fraction, sometimes exceeding 75%, can also indicate certain heart conditions, such as hypertrophic cardiomyopathy or hyperdynamic circulation. Healthcare providers consider these numerical values alongside a patient’s medical history and other diagnostic tests to form a complete picture of their heart health.
How Ejection Fraction is Measured
Ejection fraction is primarily measured using an echocardiogram, a non-invasive ultrasound of the heart. This test uses sound waves to create moving images of the heart, allowing doctors to visualize its chambers and valves in real-time and assess blood flow. It is a widely used method for determining ejection fraction.
Other methods provide additional detail and may be used in specific cases. Cardiac magnetic resonance imaging (MRI) offers detailed images of the heart’s structure and function, providing precise measurements of volumes and ejection fraction. Nuclear scans, such as a multigated acquisition (MUGA) scan, involve injecting a small amount of radioactive tracer into the bloodstream to track blood flow through the heart. These methods contribute to a comprehensive evaluation of heart pumping ability.
Common Causes of Abnormal Ejection Fraction
An ejection fraction outside the normal range often points to underlying medical conditions affecting the heart’s pumping ability. One common cause is ischemic heart disease, which includes conditions like coronary artery disease or a previous heart attack. These conditions can damage the heart muscle, leading to areas that no longer contract effectively.
Various types of cardiomyopathy, diseases of the heart muscle, can also result in an abnormal ejection fraction. Dilated cardiomyopathy causes the heart chambers to enlarge and weaken, reducing their pumping efficiency. Hypertrophic cardiomyopathy involves a thickening of the heart muscle, which can impede its ability to fill with blood. Valvular heart disease, where heart valves do not open or close properly, can force the heart to work harder, eventually leading to reduced pumping function.
Long-standing, uncontrolled high blood pressure can also strain the heart over time, causing the muscle to weaken and potentially leading to a lower ejection fraction. Certain arrhythmias, or irregular heartbeats, can disrupt the coordinated pumping action of the heart. Factors such as excessive alcohol consumption or the side effects of certain medications, including some chemotherapy drugs, can also contribute to a decline in ejection fraction by directly impacting the heart muscle’s strength.