Echo-Doppler measures how far a column of blood travels with each beat (the VTI); multiplying by the cross-sectional area of the outflow tract gives stroke volume without any invasive monitoring. An LVOT VTI below about 18 cm suggests low stroke volume.
How to use the Doppler Echo Cardiac Output Calculator
- LVOT diameter
- LVOT VTI
- Heart rate
- Height
- Weight
Results update as you type, and every field accepts the units shown in its menu.
How it works
Measure the LVOT diameter in the parasternal long-axis view and the LVOT VTI with pulsed-wave Doppler in the apical five-chamber view.
Inputs explained
| Field | What to enter |
|---|---|
| LVOT diameter | Units: cm, mm |
| LVOT VTI | In cm |
| Heart rate | In bpm |
| Height | Units: cm, in, m, ft, mm |
| Weight | Units: kg, lb, st, g |
What each result means
- Stroke volume = pi×([LVOT diameter]÷2)^2×[LVOT VTI]
- Cardiac output = [Stroke volume]×[Heart rate]÷1000
- Cardiac index = [Cardiac output]÷sqrt([Height]×[Weight]÷3600)
Example values
How the main result changes when LVOT diameter changes and everything else stays at the example values above:
| LVOT diameter (cm) | Cardiac output (L/min) |
|---|---|
| 1 | 1.1 |
| 1.5 | 2.47 |
| 2 | 4.4 |
| 2.5 | 6.87 |
| 3 | 9.9 |
| 4 | 17.59 |
Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.
Formula
LVOT area = π × (diameter ÷ 2)²
SV = LVOT area × LVOT VTI
CO = SV × HR ÷ 1000
CI = CO ÷ BSA
Worked example
Inputs — LVOT diameter: 2 cm; LVOT VTI: 20 cm; Heart rate: 70 bpm; Height: 175 cm; Weight: 75 kg.
Results — Stroke volume = 63 mL; Cardiac output = 4.4 L/min; Cardiac index = 2.3 L/min/m²; LVOT VTI = Normal (18–22 cm).
Key terms
- LVOT
- Left ventricular outflow tract.
- VTI
- Velocity-time integral.
Frequently asked questions
What is a normal LVOT VTI?
About 18–22 cm.
Why use echo to measure cardiac output?
It is non-invasive and can be repeated to see the effect of fluids or medicines.
What limits accuracy?
Measuring the LVOT diameter precisely and aligning the Doppler beam with flow.