LVOT velocity and VTI sample position
| View | Apical long-axis or five-chamber view, pulsed-wave Doppler. |
|---|---|
| Timing | Systolic ejection; average ≥3 beats (≥5 consecutive beats with irregular rhythm). |
| Caliper / trace | Sample volume just on the LV side of the aortic valve, moved into the LVOT if needed for a laminar curve; VTI traced along the modal velocity; sweep 50–100 mm/s, low wall filter. |
Correct example
Smooth, narrow-band velocity curve with a well-defined peak; the sample volume sits where the LVOT diameter was measured, and if the signal aliases, HPRF Doppler is considered rather than accepting a clipped curve.
Common error
Sampling within the valve orifice (spectral broadening, overestimated VTI) or deep in the ventricle (underestimated VTI), or tracing the outer edge of a broad signal rather than the modal velocity.
Effect on interpretation
The VTI multiplies the LVOT area directly: an overestimated VTI inflates stroke volume and AVA, an underestimated VTI produces apparent low flow and a smaller AVA.
Why
The continuity equation assumes the LVOT velocity and the LVOT area describe the same cross-section; pulsed Doppler is range-specific, so the gate position determines which flow is measured.