Ratio of blood pumped from the ventricle to the amount remaining at the end of diastole (2/3 ratio) is described by which term?

• A. Cardiac Output
• B. Ejection Fraction
• C. Stroke Volume
• D. End-Systolic Volume

Answer: (B)

The main idea is ejection fraction, which describes what fraction of the ventricle’s filling volume is pumped out with each beat. Ejection fraction is calculated as the stroke volume divided by the end-diastolic volume. If about two-thirds of the blood present at the end of filling is expelled during systole, that equals an EF of roughly 66 percent. This is why the term described is Ejection Fraction. Stroke volume is simply the amount ejected, not a ratio; cardiac output combines stroke volume with heart rate; end-systolic volume is what’s left after contraction, not the proportion ejected.