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

Answer: (C)

Ejection fraction measures the fraction of blood that is pumped out of the ventricle relative to the amount that was in the ventricle at the end of filling. The formula is stroke volume divided by end-diastolic volume, with end-diastolic volume defined at the end of diastole, when the ventricle has finished filling. Since diastole is the filling phase, the relevant boundary for the denominator is the end of diastole. That’s why the correct phase is diastole. The systolic phase is when the heart contracts and ejects blood, and the end of systole would not match the volume used in the EF calculation. Atrial systole contributes a small amount to filling but does not define the end of diastolic filling.

Ejection fraction measures the fraction of blood that is pumped out of the ventricle relative to the amount that was in the ventricle at the end of filling. The formula is stroke volume divided by end-diastolic volume, with end-diastolic volume defined at the end of diastole, when the ventricle has finished filling. Since diastole is the filling phase, the relevant boundary for the denominator is the end of diastole. That’s why the correct phase is diastole. The systolic phase is when the heart contracts and ejects blood, and the end of systole would not match the volume used in the EF calculation. Atrial systole contributes a small amount to filling but does not define the end of diastolic filling.