STROKE VOLUME CALCULATOR
- Interpreting echocardiogram (Echo) or MRI results.
- Evaluating left ventricular function and heart failure.
- Calculating combined hemodynamic metrics like Ejection Fraction (EF).
Stroke Volume (SV) is the exact amount of blood the heart pumps out in a single beat. It is essential for determining Cardiac Output and understanding the mechanical efficiency of the heart muscle.
Status
Clinical Ranges (Stroke Volume)
| Low SV | < 60 mL/beat |
| Normal SV | 60 – 100 mL/beat |
| High SV (Athletic/Hyper) | > 100 mL/beat |
Clinical Formulas
- Stroke Volume (SV): $$SV = EDV – ESV$$
- Ejection Fraction (EF): $$EF = \left( \frac{SV}{EDV} \right) \times 100$$
Stroke Volume Calculator – Calculate SV Easily (EDV–ESV)
[Image placeholder: Diagram of the heart showing End-Diastolic Volume (full ventricle) vs. End-Systolic Volume (contracted ventricle) illustrating Stroke Volume]Stroke Volume (SV) is a critical measure in cardiology that represents the volume of blood pumped out of the left ventricle of the heart during each systolic cardiac contraction (heartbeat). It is a key determinant of Cardiac Output and overall cardiovascular health.
How Stroke Volume is Calculated
In a clinical setting, such as during an echocardiogram or cardiac MRI, physicians measure Stroke Volume by comparing the size of the heart ventricle when it is completely full versus when it has finished pumping.
- End-Diastolic Volume (EDV): The amount of blood in the ventricle just before it beats (when it is most full).
- End-Systolic Volume (ESV): The amount of blood left over in the ventricle after it has pumped.
Stroke Volume Equation: $$SV = EDV – ESV$$
The Ejection Fraction (EF) Connection
You cannot talk about Stroke Volume without mentioning Ejection Fraction (EF). While Stroke Volume tells you the absolute amount of blood pumped (in mL), Ejection Fraction tells you the percentage of blood pumped relative to how full the heart was.
A normal Ejection Fraction is between 50% and 70%. A lower percentage often indicates heart failure or cardiomyopathy.
What Factors Affect Stroke Volume?
Three main hemodynamic factors govern your Stroke Volume:
| Factor | Definition | Impact on Stroke Volume |
|---|---|---|
| Preload | The degree of stretch in the heart muscle before contraction (related to EDV). | Increased Preload = Increased Stroke Volume (Frank-Starling Law). |
| Contractility | The intrinsic strength of the heart muscle. | Stronger Contractility = Increased Stroke Volume. |
| Afterload | The pressure the heart must push against to eject blood (related to blood pressure). | Increased Afterload (High BP) = Decreased Stroke Volume. |
Frequently Asked Questions (FAQs)
Why do athletes have a high stroke volume?
Endurance training physically enlarges and strengthens the heart muscle, specifically the left ventricle (a benign condition known as “athlete’s heart”). Because their heart is stronger and holds more blood (higher EDV), it pumps significantly more blood per beat. This is why highly trained athletes have very low resting heart rates—their heart doesn’t need to beat as often to deliver the required cardiac output.
Can Stroke Volume be too low?
Yes. A low Stroke Volume (typically under 50-60 mL per beat) often means the heart is failing as a pump or that not enough blood is returning to the heart (due to severe dehydration or blood loss). If the Stroke Volume drops, the heart rate usually spikes (tachycardia) to compensate and maintain Cardiac Output.
What is a normal EDV and ESV?
For an average healthy adult, normal End-Diastolic Volume (EDV) usually ranges around 120 mL, and normal End-Systolic Volume (ESV) ranges around 50 mL. This yields a normal Stroke Volume of roughly 70 mL.
Evidence and References
- Physiology, Stroke Volume – StatPearls – NCBI Bookshelf
- Ejection Fraction Heart Failure Measurement – American Heart Association
