Stroke volume is calculated as which of the following?

• A. SV = EDV − ESV.
• B. SV = ESV − EDV.
• C. SV = EDV × ESV.
• D. SV = EDV / ESV.

Answer: (A)

Stroke volume is the amount of blood the ventricle pumps with each heartbeat. It is found by subtracting the volume remaining in the ventricle after contraction from the volume in the ventricle at the end of filling: SV = EDV − ESV. This difference represents the actual blood expelled during systole. The other mathematical forms don’t reflect the amount ejected—subtracting ESV from EDV in the opposite order would give a negative value, and multiplying or dividing the volumes would yield a product or ratio, not the pumped volume per beat. For example, if EDV is about 120 mL and ESV is about 50 mL, SV is about 70 mL, with the ejection fraction being roughly 70/120 ≈ 58%.