A low Ejection Fraction (EF), also known as a low left ventricular ejection fraction (LVEF), indicates that an inadequate amount of blood is squeezed from the left ventricle with each heart beat to oxygenate the body. Measured variously by echocardiogram, cardiac catherization, during a cardiac stress test or other diagnostic testing, a normal ejection fraction is usually 50 to 70 percent of the ventricular volume. A low ejection fraction is considered to be 35 to 40 percent, or less, of ventricular volume and is indicative of systolic heart failure or congestive heart failure (CHF). Effects of a low EF are similar to that of an unexpected road block on traffic: the blood, like traffic, backs up and "stalls" in the lungs and the body's extremities. These effects produce the symptoms characteristic of congestive heart failure such as shortness of breath, fatigue and edema.
A quick review of cardiovascular anatomy and physiology helps explain the effects of a low ejection fraction. The larger and more muscular lower left ventricle is designed to pump oxygenated blood to the rest of the body and receives blood from the heart's upper left atrium which, in turn, receives oxygen-rich blood from the pulmonary artery. When the left ventricle only ejects less than half its volume, blood backs up through the system to the lungs. Excess blood and fluid in the pulmonary tissue results in shortness-of-breath and a frequent, chronic, unproductive cough. The shortness-of-breath intensifies when the patient lies down and the backed up blood is allowed to flow, unimpeded by gravity, congesting the lungs.
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The backup of blood secondary to the left ventricle's low ejection fraction also extends to the extremities. Blood pools in the usually dependent lower limbs, causing edema from the excess fluid. This situation can worsen as the excess fluid then prevents oxygenated blood from reaching these tissues. A characteristic bluish tint often results and skin breakdown may occur.
A low ejection fraction also results in long-term hypoxia, or low oxygenation, to the all tissues of the body. Chronic hypoxia results in extreme fatigue and very early onset weakness with most physical activity. Reasoning and memory may be cloudy and intermittent confusion can result with low oxygen levels in the brain. The heart — a muscle itself — can be affected by the hypoxic situation and develop irregular heart beats. Heart murmurs can result from the blood backing up as well.