Velocity Time Integral (VTI)
- Velocity Time Integral (VTI) is the area under the curve on a Pulse Wave Doppler tracing. It represents the distance blood travels during one heartbeat. In the LVOT (Left Ventricular Outflow Tract), the Doppler tracing shows velocity on the Y-axis and time on the X-axis. By calculating the area under this curve (VTI), and multiplying it by the cross-sectional area of the LVOT, you can estimate stroke volume.
- Stroke Volume = LVOT area × VTI
- LVOT area = π × (LVOT radius)²