Ejection fraction is defined as what?

• A. Percent of blood pushed out each contraction
• B. End diastolic volume
• C. Stroke volume
• D. Cardiac Output

Answer: (D)

Ejection fraction is the percentage of blood in the ventricle at the end of filling (end diastole) that gets pumped out with each heartbeat. It’s calculated as stroke volume divided by end-diastolic volume, then multiplied by 100. So EF = (SV / EDV) × 100. For example, if the ventricle fills with 120 mL (EDV) and 70 mL is ejected (SV), the EF is about 58%. This shows how efficiently the heart ejects blood per beat. It’s not simply the volume in the ventricle (EDV), nor the amount ejected in absolute volume (SV), nor the overall flow per minute (cardiac output, which is SV × heart rate).