Which equation represents end-systolic volume?

Which equation represents end-systolic volume?

• A. ESV = EDV - SV
• B. ESV = SV - EDV
• C. ESV = EDV + SV
• D. ESV = SV / EDV

Answer: (A)

The key relationship here is how volumes change from diastole to systole. End-diastolic volume (EDV) is the amount in the ventricle before contraction, and stroke volume (SV) is how much is ejected during contraction. The amount ejected plus the amount left behind must equal what you started with: SV = EDV − ESV. Solving for ESV gives ESV = EDV − SV. That’s why this form correctly represents end-systolic volume. For example, if EDV is 120 mL and SV is 70 mL, ESV would be 50 mL. The other forms would misrepresent the relationship (adding volumes or swapping the order) and could yield nonsensical results in typical physiology.

The key relationship here is how volumes change from diastole to systole. End-diastolic volume (EDV) is the amount in the ventricle before contraction, and stroke volume (SV) is how much is ejected during contraction. The amount ejected plus the amount left behind must equal what you started with: SV = EDV − ESV. Solving for ESV gives ESV = EDV − SV. That’s why this form correctly represents end-systolic volume.

For example, if EDV is 120 mL and SV is 70 mL, ESV would be 50 mL. The other forms would misrepresent the relationship (adding volumes or swapping the order) and could yield nonsensical results in typical physiology.