Stroke Volume Calculator

What is Stroke Volume?

Stroke Volume (SV) is the volume of blood pumped out of the left ventricle of the heart during each systolic contraction. Measured in milliliters per beat ($\text{mL/beat}$), stroke volume is a cornerstone parameter in cardiology, critical care, and anesthesiology for assessing cardiac systolic performance and tissue perfusion.

In healthy resting adults, typical stroke volume ranges between 60 and 100 mL/beat, influenced by three fundamental physiological determinants:

Preload: The degree of myocardial sarcomere stretch at end-diastole, governed by venous return and end-diastolic volume.
Afterload: The vascular resistance and systemic arterial pressure against which the ventricle must contract to eject blood.
Myocardial Contractility (Inotropy): The intrinsic contractile force of the ventricular muscle independent of loading conditions.

Calculation Methods & Formulas

1. Volumetric Method (Echocardiography / MRI)

The direct difference between the end-diastolic volume ($\text{EDV}$) and end-systolic volume ($\text{ESV}$):

$$\text{SV} = \text{EDV} - \text{ESV}$$

The associated Ejection Fraction (EF) is computed as:

$$\text{EF (\%)} = \left(\frac{\text{EDV} - \text{ESV}}{\text{EDV}}\right) \times 100$$

2. Hemodynamic Method (from Cardiac Output & Heart Rate)

$$\text{SV (mL/beat)} = \frac{\text{Cardiac Output (L/min)} \times 1000}{\text{Heart Rate (bpm)}}$$

3. Doppler Echocardiography (LVOT VTI Method)

Using pulsed-wave Doppler through the left ventricular outflow tract (LVOT):

$$\text{LVOT Area} = \pi \times \left(\frac{D_{\text{LVOT}}}{2}\right)^2 \approx 0.7854 \times D_{\text{LVOT}}^2$$

$$\text{SV} = \text{LVOT Area} \times \text{LVOT VTI}$$

Indexed Hemodynamic Parameters

Because cardiac requirements correlate with body size, parameters are normalized using Body Surface Area (BSA):

Stroke Volume Index (SVI): $\text{SVI} = \frac{\text{SV}}{\text{BSA}}$ (Normal: $33\text{--}47\text{ mL/beat/m}^2$)
Cardiac Index (CI): $\text{CI} = \frac{\text{Cardiac Output}}{\text{BSA}}$ (Normal: $2.5\text{--}4.0\text{ L/min/m}^2$)

Explore related tools: check out our Cardiac Output Calculator and Cardiac Index Calculator.

Frequently Asked Questions

What causes low stroke volume?

Low stroke volume can stem from hypovolemia (dehydration, hemorrhage), acute myocardial infarction, systolic heart failure, severe mitral or aortic valvular stenosis, cardiac tamponade, or extreme tachycardia where diastolic filling time is drastically reduced.

How does exercise affect stroke volume?

During exercise, enhanced sympathetic inotropic tone and increased skeletal muscle venous return raise stroke volume significantly (often up to 120–150 mL in trained endurance athletes) before plateauing at high heart rates.

What is the Frank-Starling Law of the Heart?

The Frank-Starling mechanism describes the relationship between end-diastolic volume and contractile force: greater ventricular filling (preload) increases myocardial fiber stretch, which augments cross-bridge formation and enhances the subsequent force of contraction, thereby increasing stroke volume.

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