Doppler Echo Cardiac Output Calculator
HealthCalculate stroke volume and cardiac output from LVOT diameter, LVOT VTI, and heart rate using the standard non-invasive Doppler echocardiography method.
LVOT Diameter
cm
LVOT VTI
cm
Heart Rate
bpm
Cardiac Output
0L/min
Stroke Volume0 mL
LVOT Cross-Sectional Area0 cm²
Not a substitute for clinical interpretation. Doppler-derived hemodynamic values should be reviewed alongside the full echocardiographic study by a qualified healthcare provider.
What is a Doppler Echo CO?
The Doppler Echo Cardiac Output Calculator computes stroke volume and cardiac output using the standard non-invasive Doppler echocardiography method, based on the left ventricular outflow tract (LVOT) diameter, LVOT velocity time integral (VTI), and heart rate. This is the same flow-based calculation routinely performed during a transthoracic echocardiogram to assess how much blood the heart is pumping.
Enter your LVOT diameter, VTI, and heart rate below to see your calculated stroke volume and cardiac output. For a body-size-adjusted version of this measurement, see the Cardiac Index Calculator; for a related valve area calculation using the same LVOT concept, see the Aortic Valve Area Calculator.
How to use this Doppler Echo CO calculator
- Enter your LVOT Diameter in centimeters, as measured on echocardiography.
- Enter your LVOT VTI in centimeters, from the pulsed-wave Doppler tracing.
- Enter your Heart Rate in beats per minute.
- Review your calculated Cardiac Output, Stroke Volume, and LVOT Cross-Sectional Area.
Formula & Methodology
LVOT Cross-Sectional Area (cm²) = π × (LVOT diameter ÷ 2)² Stroke Volume (mL) = LVOT Cross-Sectional Area × LVOT VTI Cardiac Output (L/min) = (Stroke Volume × Heart Rate) ÷ 1000 This is the standard flow-based, non-invasive cardiac output method used routinely in transthoracic echocardiography, relying on the principle that flow through the LVOT during systole equals the product of its cross-sectional area and the velocity-time integral of blood moving through it. Worked example: An LVOT diameter of 2.0 cm gives a cross-sectional area of π × 1² ≈ 3.14 cm². With an LVOT VTI of 20 cm, stroke volume = 3.14 × 20 ≈ 62.8 mL. At a heart rate of 70 bpm, cardiac output = (62.8 × 70) ÷ 1000 ≈ 4.4 L/min, a typical resting value for an average-sized adult.
Frequently Asked Questions
This calculator uses the standard non-invasive Doppler echocardiography method for measuring cardiac output, based on the left ventricular outflow tract (LVOT) diameter and velocity time integral (VTI). It's the same underlying flow calculation used in routine transthoracic echocardiogram studies.
LVOT diameter is used to calculate the cross-sectional area of the outflow tract, assuming a circular shape, using the formula pi times (diameter divided by 2) squared. This area, combined with the LVOT velocity time integral, determines stroke volume for each heartbeat.
The LVOT velocity time integral (VTI) represents the distance blood travels through the outflow tract during one heartbeat, measured from the Doppler velocity waveform on echocardiography. Multiplying VTI by the LVOT cross-sectional area gives stroke volume, the amount of blood ejected per heartbeat.
Stroke volume is the amount of blood ejected by the heart in a single beat, measured in milliliters, while cardiac output is the total volume pumped per minute, measured in liters per minute. Cardiac output is calculated by multiplying stroke volume by heart rate and dividing by 1000 to convert units.
Unlike catheterization-based methods such as the Gorlin formula or thermodilution, the Doppler echocardiography method only requires external ultrasound measurements taken during a standard echocardiogram, without inserting any catheter into the heart or blood vessels. This makes it the most commonly used method for everyday clinical cardiac output assessment.
A typical resting adult cardiac output falls roughly between 4 and 8 liters per minute, though the specific normal range depends on body size, which is why cardiac index (cardiac output adjusted for body surface area) is often used for a more individualized assessment. See the [Cardiac Index Calculator](/cardiac-index-calculator/) for that adjusted measure.
When measurements are taken carefully by an experienced sonographer, the Doppler echo method generally correlates well with invasive thermodilution or Fick method cardiac output values, though it does depend on accurate LVOT diameter measurement, which can introduce some variability. It remains the standard first-line non-invasive approach in most echocardiography labs.
Because LVOT diameter is squared in the cross-sectional area formula, small measurement errors in diameter are amplified more than similar errors in VTI or heart rate. Careful, reproducible diameter measurement from the parasternal long-axis view is considered the most important technical factor for an accurate result.
No — this calculator is for informational and educational purposes only and simply performs the standard flow calculation from values you enter. Actual measurement of LVOT diameter and VTI requires a properly performed echocardiogram interpreted by a qualified sonographer or cardiologist, and results should always be reviewed by a healthcare provider.
The [Gorlin Formula Calculator](/gorlin-formula-calculator/) calculates valve area from invasive catheterization data including cardiac output, while this calculator estimates cardiac output itself from non-invasive Doppler measurements. The cardiac output value calculated here could, in principle, feed into a Gorlin formula calculation if catheterization data were also available.
The [Aortic Valve Area Calculator](/aortic-valve-area-calculator/) uses a similar LVOT-based continuity equation approach but focuses on valve area rather than overall cardiac output, and requires an additional velocity measurement across the aortic valve itself. Both tools rely on the same LVOT cross-sectional area concept.
Cardiac output is directly proportional to heart rate in this calculation — a higher heart rate with the same stroke volume produces a proportionally higher cardiac output. This is why cardiac output can change significantly between rest and exercise even if stroke volume stays relatively stable.
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