EF is the fraction of blood pumped out of the right and left ventricles with each heartbeat. What measurement does this describe?

• A. The speed of heart contraction
• B. The rate of blood flow through a valve
• C. The fraction of blood pumped out of the right and left ventricles with each heartbeat
• D. The amount of blood in the atria

Answer: (C)

Ejection fraction describes how effectively the heart pumps blood with each beat. It’s the fraction of blood in the ventricle at the end of filling (end-diastolic volume) that is ejected during systole, expressed as a percentage. The typical way to think of it is: stroke volume divided by end-diastolic volume. This measure reflects systolic function for the ventricles. Normal values are generally about 55–70% for the left ventricle. A reduced ejection fraction indicates impaired pumping ability, as seen in systolic heart failure. The other options describe different concepts: the speed of contraction relates to heart rate or contractility, the rate of blood flow through a valve is about instantaneous flow, and the amount of blood in the atria refers to preload or atrial volume rather than ventricular ejection performance.