TVI (or VTI) is a hemo-dynamic echo parameter measured from Doppler spectrum across the valves ,usually in the outflow.This parameter is used to calculate cardiac output .VTI times the cross sectional area gives the stroke volume.
A correction: TVI is multiplication of velocity into time not division as suggested in the cartoon
Time velocity Integral
Summary
*VTI is a Doppler parameter described in cm , it can be referred to as Stroke distance.This stroke distance when multiplied by valve area gives the stroke volume from LV/RV (or flow volume across AV valves or through any conduit)
Dr.S.Venkatesan MD 