SME
Human Anatomy & Physiology · Problem type
Stroke volume and ejection fraction
Use this for “End-diastolic volume 120 mL, end-systolic 50 mL. What are the stroke volume and ejection fraction?”
Diagram
SV = EDV − ESV = 120 mL − 50 mL
SV = 70 mL
EF
=
SV
EDV
=
58.3%.
CO = HR × SV = 70 min⁻¹ × 70 mL
CO = 4.90 L/min
This is an example. Type your own values to start a new problem.
SV (mL)
=
EDV (mL)
−
ESV (mL)
EF
%
=
SV (mL)
EDV (mL)
×
100
HR
Heart rate
example · min⁻¹
CO
Cardiac output
calculated · L/min
Formulas
SV = EDV − ESV
70 = 120 − 50
EF
=
SV
EDV
×
100
58.3
=
70
120
×
100
CO
=
HR
×
SV
1,000
4.9
=
70
×
70
1,000
Assumptions
•
End-diastolic volume (EDV) is the blood in the left ventricle when it is fullest, just before it contracts.
•
End-systolic volume (ESV) is the blood left in it after it contracts; the stroke volume is the difference.
•
The ejection fraction is the share of EDV pushed out each beat, about 55 to 70% in a healthy heart.
Step-by-step
WE KNOW
EDV = 120 mL, ESV = 50 mL, HR = 70 min⁻¹
FIND
stroke volume (SV), ejection fraction (EF), cardiac output (CO)
Step 1 · Find stroke volume (SV)
Use SV = EDV − ESV
What the ventricle held when full minus what was left after it contracted.
SV = 120 − 50
SV = 70 mL
Step 2 · Find ejection fraction (EF)
Use EF = SV ÷ EDV × 100
The share of the full ventricle pushed out, written as a percent.
EF
=
70
120
×
100
EF = 0.5833 × 100
EF = 58.3%
Step 3 · Find cardiac output (CO)
Use CO = HR × SV ÷ 1,000
Each beat pushes out one stroke volume, HR times a minute; 1,000 mL make 1 L.
CO
=
70
×
70
1,000
CO
=
4,900
1,000
CO = 4.9 L/min
Check
Put the numbers back in. Both sides should match.
70 = 120 − 50 ✓
58.3
=
70
120
×
100
✓
4.9
=
70
×
70
1,000
✓
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