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Ejection fraction measures the percentage of blood pumped from a ventricle with each heartbeat. It is used to determine prognosis in heart patients and is measured through various imaging techniques. A normal LVEF ranges from 50 to 70%.
An ejection fraction is a measurement of what percentage of blood is pumped from one ventricle into the heart with each beat. It is usually measured from the left ventricle, which is the main pumping chamber in the heart. It is sometimes qualified as right ventricular ejection fraction (RVEF) to refer to the amount of blood delivered to the lungs.
During a heartbeat, the heart muscle contracts and relaxes like any other muscle during activity. The relaxation allows the ventricles, or chambers, to fill with blood. The contraction draws blood out. The strength of the heart and the clarity of the arteries determine how much blood will be ejected and circulated throughout the body.
The blood in a ventricle just before it contracts is called the end-diastolic volume. The volume left in the ventricle after the contraction is the end-systolic volume. If you subtract end-systolic volume from end-diastolic volume, you get a number called stroke volume. The ejection fraction is obtained by dividing the stroke volume by the end-diastolic volume. In effect, this is the percentage of end diastolic volume that has been forced into each beat.
For an average healthy man weighing approximately 154 lbs (70 kg), stroke volume should be approximately 2.4 oz (70 mL) and end diastolic volume should be approximately 4.1 oz (120 mL). This makes the ejection fraction 2.4/4.1 or 70/120 which is about 58%. A normal left ventricular ejection fraction (LVEF) ranges from 50 to 70%, but it can be reduced by heart damage or other heart problems.
Cardiologists use ejection fraction to determine prognosis in patients suffering from a variety of ailments, not least of which are angina or chest pain. The following numbers are approximate ranges for LVEF and their indications: 50-70% is normal, 36-49% is less than normal, 35-40% may indicate systolic heart failure, and less than 35% is considered life-threatening and irregular. If the ejection fraction is found to be in this lowest category, immediate action is taken to prevent complete heart failure.
Ejection fraction is measured with various imaging techniques. An ultrasound, also called an echocardiogram, uses sound waves to produce pictures of the heart. Cardiac catheterization involves a thin tube placed into a leg vein and into the heart, while magnetic resonance imaging (MRI) uses magnetic fields and radio waves to create cross-sections of the body. Cardiac computed tomography (CT) is a more complex version of an X-ray, and a Multiple Gated Acquisition (MUGA) scan uses a small amount of radioactive material in the bloodstream combined with special cameras to create a visualization of the blood pumping.
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