Stroke volume is defined as what?

• A. The volume of blood ejected by the heart per minute.
• B. The amount of blood pumped out of a ventricle during each contraction.
• C. The amount of blood in ventricles after diastole.
• D. The number of heart beats per minute.

Answer: (B)

Stroke volume is the amount of blood ejected by a ventricle with each contraction. It’s the volume the heart pumps on every beat, and it’s calculated as the difference between end-diastolic volume (the blood in the ventricle after filling) and end-systolic volume (the blood remaining after contraction). This is different from cardiac output, which is the total blood pumped per minute (stroke volume times heart rate). It’s also distinct from end-diastolic volume itself and from heart rate, which is how many beats occur per minute. In a typical adult, stroke volume is about 60–80 mL per beat, though it varies with preload, afterload, and contractility.