Ejection fraction is defined as the ratio of blood pumped from the ventricle to the amount remaining at the end of which phase?

Ejection fraction is defined as the ratio of blood pumped from the ventricle to the amount remaining at the end of which phase?

• A. Diastole
• B. Systole
• C. Isovolumetric relaxation
• D. Atrial systole

Answer: (A)

Ejection fraction is the portion of blood in the ventricle that is pumped out with each heartbeat, expressed as stroke volume divided by end-diastolic volume. The end-diastolic volume is the amount remaining at the end of diastole, right before systole begins, when the ventricle has just finished filling. So the ratio targets how much was present at the end of filling (diastole) and how much is ejected during contraction. That’s why diastole is the relevant phase. The other options don’t fit: end of systole would involve the end-systolic volume, isovolumetric relaxation involves no change in volume, and atrial systole contributes to filling but EF uses the full end-diastolic volume, not just the portion from atrial contraction.

Ejection fraction is the portion of blood in the ventricle that is pumped out with each heartbeat, expressed as stroke volume divided by end-diastolic volume. The end-diastolic volume is the amount remaining at the end of diastole, right before systole begins, when the ventricle has just finished filling. So the ratio targets how much was present at the end of filling (diastole) and how much is ejected during contraction. That’s why diastole is the relevant phase. The other options don’t fit: end of systole would involve the end-systolic volume, isovolumetric relaxation involves no change in volume, and atrial systole contributes to filling but EF uses the full end-diastolic volume, not just the portion from atrial contraction.