Cardiac Output

LVOT VTI CO Calculator

Calculates CO and optional CI

CI Inputs

LVOT VTI to Measure Cardiac Output

LVOT Area = π × (LVOT diameter / 2)²

Units

  • Diameter in cm
  • VTI in cm
  • SV in mL
  • CO in L/min

Step 1: Measure LVOT Diameter

View: Parasternal long axis
Timing: Mid systole
Method: Inner edge to inner edge
Location: Just proximal to the aortic valve annulus

Diameter is squared in the equation. Small measurement errors create HUGE CO errors.

Step 2: Measure LVOT VTI

View: Apical 5 chamber (usually best) or apical 3 chamber
Doppler: Pulsed wave

How to do it

  1. Place PW Doppler sample gate 0.5 to 1.0 cm proximal to the aortic valve, on the LV side.
  2. Align Doppler beam as parallel to LVOT flow as possible.
  3. Increase sweep speed.
  4. Trace the outer edge of the Doppler envelope.
  5. Average:
    • 3 beats in sinus rhythm
    • 5 to 10 beats in atrial fibrillation

Step 3: Calculate Stroke Volume

  • Stroke Volume = LVOT Area × LVOT VTI

Step 4: Calculate Cardiac Output

  • CO = SV × HR