How to Calculate Stroke Volume
Stroke volume is the amount of blood pumped by the left ventricle of the heart in one contraction. It is an important measure of heart function in medical physiology.
Stroke Volume Formula
SV = EDV - ESV
Where:
- SV = Stroke Volume
- EDV = End-Diastolic Volume (volume of blood in the ventricle at the end of filling)
- ESV = End-Systolic Volume (volume of blood remaining in the ventricle after contraction)
Stroke volume is typically measured in milliliters (mL).
SV = CO ÷ HR
Alternatively, stroke volume can be calculated using:
- CO = Cardiac Output (volume of blood pumped by the heart in one minute)
- HR = Heart Rate (number of heartbeats per minute)
Step-by-Step Guide
Method 1: Using EDV and ESV
- Measure the End-Diastolic Volume (EDV)
This is the volume of blood in the ventricle at the end of filling.
- Measure the End-Systolic Volume (ESV)
This is the volume of blood remaining in the ventricle after contraction.
- Calculate the difference
Subtract ESV from EDV to find the stroke volume: SV = EDV - ESV.
Method 2: Using Cardiac Output and Heart Rate
- Measure the Cardiac Output (CO)
This is the total volume of blood pumped by the heart in one minute (L/min).
- Measure the Heart Rate (HR)
Count the number of heartbeats per minute.
- Calculate the ratio
Divide CO by HR to find the stroke volume: SV = CO ÷ HR.
Note: If CO is in L/min, you'll need to convert to mL by multiplying by 1000 for SV in mL.
Example Calculation
Problem: Calculate the stroke volume for a patient with an EDV of 120 mL and an ESV of 50 mL.
Given: EDV = 120 mL, ESV = 50 mL
Solution:
- Apply the formula: SV = EDV - ESV
- Substitute the values: SV = 120 - 50
- Compute the result: SV = 70 mL
Answer: The stroke volume is 70 milliliters (mL).
Problem: Calculate the stroke volume for a patient with a cardiac output of 5.25 L/min and a heart rate of 75 beats per minute.
Given: CO = 5.25 L/min, HR = 75 bpm
Solution:
- Apply the formula: SV = CO ÷ HR
- Convert CO from L/min to mL/min: 5.25 L/min × 1000 = 5250 mL/min
- Substitute the values: SV = 5250 ÷ 75
- Compute the result: SV = 70 mL
Answer: The stroke volume is 70 milliliters (mL).
Normal Values and Clinical Significance
The normal stroke volume for an average-sized adult is approximately 70 mL, but can range from 50-100 mL depending on factors such as:
- Body size
- Age
- Gender
- Physical fitness
- Heart health
Clinically, stroke volume is important for assessing:
- Cardiac function
- Heart failure
- Valvular heart disease
- Response to treatment
- Exercise capacity
Related Calculations
Ejection Fraction
EF = (SV ÷ EDV) × 100%
The percentage of blood ejected from the ventricle with each contraction.
Cardiac Output
CO = SV × HR
The total volume of blood pumped by the heart in one minute.