Healthy Circulatory System
A Answers (6)
The amount of blood that is pumped out by the heart in one beat is called the ejection fraction.
An ejection fraction reflects the strength of the heart muscle. The normal ejection fraction for the left ventricle is 50% to 60%. The heart muscle may be weakened from a heart attack, heart failure, or an infection. Any weakening of the heart muscle may lower the ejection fraction.
The heart has four chambers, the right and left atrium, and the right and left ventricle. Oxygen-poor blood from the body enters the right atrium, where it is delivered to the right ventricle to be pumped to the lungs to receive oxygen. Once the blood receives oxygen, it enters the left atrium, and is delivered to the left ventricle, which pumps it to the rest of the body. In the heart are four valves that prevent blood flowing backwards. Changes in the proper function of these valves can occur, causing related valvular disorders, such as mitral valve (the valve between the left atrium and left ventricle) prolapse (MVP). The aortic valve is responsible for preventing reverse blood flow so that blood leaves the left ventricle to enter the artery. The time between the opening of the aortic valve for release of blood from the left ventricle to closure of the valve is known as the left ventricular ejection time (LVET). With some diseases of the heart, the LVET may be reduced.
Immediately before a heart contraction there is a certain volume of blood within the ventricle. This is called the end-diastolic volume (EDV). After the contraction, there is a certain amount of blood left in the ventricle and this is called the end-systolic volume (ESV). The difference between these (EDV-ESV) is the stroke volume (SV). The ejection fraction (EF) is the SV divided by the EDV (SV/EDV), and is often expressed as a percentage, with normal values being 50-70%. EF can be defined as the amount of blood pumped by the heart into circulation with each heartbeat. Although EF can refer to either the left ventricle or the right ventricle, it is the left ventricular function that is more commonly investigated, because it is the left ventricle that pumps the blood to the body.
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The ejection fraction is a measure of how well the heart is pumping blood. The measurement describes the percent of blood inside the ventricle chamber that is pumped into the body with each heartbeat. A healthy ejection fraction is 55 to 60 percent of the blood inside the ventricle. This measurement is often taken during an echocardiogram, a test that uses sound waves to make an image of the heart.