Doppler Echo Cardiac Output Calculator
Compute cardiac output (CO) and cardiac index (CI) from a transthoracic echocardiogram using the pulsed-wave Doppler LVOT method — the gold standard non-invasive technique in clinical cardiology.
cm
cm
bpm
cm
kg
Normal range: 4.0–8.0 L/min at rest
- 1
LVOT cross-sectional area
π × (2 ÷ 2)² = 3.142 cm²Area = π × r²; LVOT diameter measured at the aortic annulus in PLAX view. - 2
Stroke volume
3.142 cm² × 22 cm = 69.1 mL - 3
Cardiac output
69.1 mL × 70 bpm ÷ 1000 = 4.84
How does this calculator work?
CO = π × (LVOT_d/2)² × VTI × HR ÷ 1000 (L/min). Typical values: LVOT d ≈ 2.0 cm, VTI ≈ 22 cm, HR = 70 bpm → CO ≈ 4.8 L/min. Cardiac index = CO ÷ BSA; normal is 2.5–4.0 L/min/m². LVOT diameter measurement is the largest source of error — a 1 mm change shifts CO by ~5–10 %.
Formula
How this is calculated
The Doppler echocardiography method for cardiac output uses the left ventricular outflow tract (LVOT) as a surrogate for a flow cylinder. The cross-sectional area of the LVOT is calculated from its diameter (d) measured in the parasternal long-axis view at the level of the aortic annulus: Area = π × (d/2)². The velocity-time integral (VTI) — the area under the Doppler spectral envelope traced at the LVOT using pulsed-wave Doppler from the apical five-chamber view — represents the column length of blood ejected per beat (in cm). Stroke volume (SV, mL) is then Area × VTI, and cardiac output CO (mL/min) = SV × HR, converted to L/min by dividing by 1,000.
Cardiac index (CI) normalises CO for body surface area (BSA) to allow comparison across differently sized patients. BSA is estimated using the Du Bois formula (1916): BSA = 0.007184 × height^0.725 × weight^0.425. A CI of 2.5–4.0 L/min/m² is considered normal at rest; values below 2.2 L/min/m² suggest cardiogenic shock.
Accuracy depends critically on correct LVOT diameter measurement — because the area uses d², a 1 mm error in diameter propagates to a ~5–10 % error in CO. Ensure the LVOT diameter is measured in systole at the hinge points of the aortic valve leaflets. This calculator is a clinical aid and should be used by trained clinicians alongside full echocardiographic evaluation.
Frequently asked questions
At rest, normal cardiac output is approximately 4–8 L/min for adults. Cardiac index (CO adjusted for body surface area) should be 2.5–4.0 L/min/m². Values vary with activity, temperature, anxiety, and haemodynamic state.
Because area = π × (d/2)², any error in diameter is squared in its effect on area and therefore CO. A 1 mm underestimation in a 2 cm LVOT (5 % error in d) causes ~10 % underestimation of CO. Careful measurement in the correct view and plane is essential.
Yes, but with reduced accuracy. In atrial fibrillation, stroke volume varies beat-to-beat, so VTI should be averaged over at least five consecutive beats. Consider using a beat-averaged VTI for a more reliable estimate.
TG we-Calculate Editorial Team. (2026). Doppler Echo Cardiac Output Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/doppler-echo-cardiac-output-calculator
TG we-Calculate Editorial Team. "Doppler Echo Cardiac Output Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/doppler-echo-cardiac-output-calculator.
TG we-Calculate Editorial Team, "Doppler Echo Cardiac Output Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/doppler-echo-cardiac-output-calculator
@misc{wecalculate_doppler_echo_cardiac_output_calculator, title = {Doppler Echo Cardiac Output Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/doppler-echo-cardiac-output-calculator}}, year = {2026}, note = {TG we-Calculate} }
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