Enter the Left Ventricular Outflow Tract (LVOT) diameter, the Velocity Time Integral (VTI), and the heart rate into the calculator to determine the cardiac output. This calculator uses echocardiographic measurements to estimate the volume of blood the heart pumps through the circulatory system in a minute.

Cardiac Output Echo Calculator

Enter any 3 values to calculate the missing variable (LVOT diameter, VTI, heart rate, or cardiac output).

Educational use only (not medical advice): This tool provides an estimate of cardiac output from Doppler echo measurements and must be interpreted by a qualified clinician. Intended for clinicians/trainees familiar with Doppler echo acquisition. Results depend heavily on measurement technique (e.g., LVOT assumed circular, LVOTD measurement variability, Doppler alignment). Do not use this tool to make diagnosis or treatment decisions. If you have chest pain, shortness of breath, fainting, or other emergency symptoms, seek emergency care.

Measurement notes

In typical practice, LVOT diameter is measured inner-edge to inner-edge in mid-systole (parasternal long-axis), and LVOT VTI is traced with pulsed-wave Doppler just proximal to the aortic valve with careful Doppler alignment. For detailed acquisition guidance and limitations, consult professional echocardiography guideline documents (for example, American Society of Echocardiography guidance).

Related Calculators

Cardiac Output Echo Formula

The following formula is used to calculate the cardiac output using echocardiographic measurements:

CO = (ฯ€ * (LVOTD / 2)^2 * VTI * HR) / 1000

Variables:

  • CO is the cardiac output (L/min)
  • LVOTD is the Left Ventricular Outflow Tract Diameter (cm)
  • VTI is the Velocity Time Integral (cm)
  • HR is the heart rate (beats per minute)

To calculate the cardiac output, first measure the LVOT diameter and VTI using echocardiography. Then, multiply the LVOT area by the VTI to get stroke volume per beat, and multiply by the heart rate. Finally, divide the result by 1000 to convert it to liters per minute (L/min).

What is Cardiac Output?

Cardiac output is the volume of blood the heart pumps per minute. It is a critical parameter in assessing cardiac function and is used to diagnose and monitor patients with heart conditions. Cardiac output is determined by the stroke volume (the amount of blood pumped by the left ventricle of the heart in one contraction) and the heart rate (the number of heartbeats per minute).

How to Calculate Cardiac Output?

The following steps outline how to calculate the Cardiac Output using echocardiographic measurements.

  1. Measure the LVOT diameter (LVOTD) in centimeters using echocardiography.
  2. Measure the VTI in centimeters using Doppler echocardiography.
  3. Record the patient’s heart rate (HR) in beats per minute.
  4. Calculate the LVOT area using the formula: Area = ฯ€ * (LVOTD / 2)^2.
  5. Calculate stroke volume per beat using: Stroke volume (mL/beat) = LVOT area (cmยฒ) ร— VTI (cm).
  6. Calculate cardiac output using: Cardiac output (L/min) = stroke volume (mL/beat) ร— HR (beats/min) รท 1000.
  7. Use the calculator above to verify your results.

Example Problem:

Use the following variables as an example problem to test your knowledge.

LVOT Diameter (LVOTD) = 2 cm

Velocity Time Integral (VTI) = 20 cm

Heart Rate (HR) = 75 bpm