The volume of blood in the ventricle at the end of diastole is known as what?

• A. End-diastolic volume
• B. Stroke volume
• C. Cardiac output
• D. Afterload

Answer: (A)

End-diastolic volume is the volume of blood in the ventricle at the end of diastole, after filling and just before contraction. This represents preload—the amount the ventricle is stretched by incoming blood. The greater this filling volume (within normal limits), the stronger the subsequent contraction tends to be, via the Frank-Starling mechanism, which helps determine how much blood the heart will eject on the next beat.

Stroke volume is how much blood is ejected during systole (EDV minus end-systolic volume), cardiac output is stroke volume times heart rate, and afterload is the pressure the ventricle must overcome to eject blood (related to arterial pressure and systemic vascular resistance).