Approximately how many milliliters are ejected per beat by the ventricle in a healthy adult?

• A. 50 mL
• B. 70 mL
• C. 90 mL
• D. 110 mL

Answer: (B)

Stroke volume is the amount the ventricle pumps with each beat. In a healthy adult at rest, this is about 70 mL. This comes from typical volumes: end-diastolic around 120 mL minus end-systolic around 50 mL gives roughly 70 mL per beat. If heart rate is about 70 beats per minute, cardiac output is about 5 L per minute (70 mL × 70/min), which fits resting values. Values around 50 mL are a bit low for rest, around 90 mL can occur with higher demand or conditioning, and about 110 mL is generally seen with greater exercise load. So the best approximate resting ejected volume per beat is 70 mL.