What is the ejection fraction, and why is it clinically important?

• A. EF = (EDV − ESV) / EDV; normal about 55–70%
• B. EF = ESV / EDV; normal about 40–50%
• C. EF = (EDV − ESV) / ESV; normal about 55–70%
• D. EF = EDV / ESV; normal about 60–90%

Answer: (A)

Ejection fraction shows how well the left ventricle pumps out the blood it has just filled with. It is the fraction of end-diastolic volume that is ejected during systole. Since stroke volume equals EDV minus ESV, EF is calculated as (EDV − ESV) / EDV, which is the same as SV/EDV. The normal range is about 55–70%.

This measure is clinically important because it reflects systolic function. A reduced EF indicates the heart isn’t contracting effectively, as seen in conditions like heart failure with reduced ejection fraction, and it helps guide treatment decisions and prognosis. EF is commonly measured with imaging tests such as echocardiography.