Formula:AVG = 4 * ReferenceVelocity² - 4 * PeakVelocity²
How to get an Pulmonary Valve Gradient by Peak Velocity.
- Obtain a continuous wave doppler of the pulmonary valve. The optimal view is the short axis of the aortic arch. In this view the pulmonary valve is in it's long axis and provides the best angle to doppler the gradient's across the valve. An alternative view is the deep transgastric view around 90 degrees. The pulmonic valve should be viewable in most instances, however, the angle for the doppler scan may be off more than 20 degrees. Once the view is obtained turn on the CWD and use the track ball to move the CWD line to the pulmonary valve. A doppler profile of the pulmonary valve should be displayed with high velocities in pulmonary stenosis. If a poor or low velocity doppler wave form is displayed reposition the view and move the CWD line thru out the valve. The CWD must be parallel to the stenotic jet to pick up the maximal velocity and obtain a good doppler wave form. After a good doppler wave form is obtained look at the morphology of the waveform and note it. A profile that has a large gradient across the valve will exhibit a "filling in" pattern, whereas a low or normal gradient flow profile will have a scattered filled in pattern. The amount of filling of the flow profile is related to the amount of turbulence across the valve. Place the trackball point at the peak of the flow profile and note the velocity.
- Obtain a pulse wave doppler of the RVOT. The views listed above will provide a RVOT scan, however, the deep transgastric is preferable because of a more accurate scan. Once the view is obtained turn on the PWD and use the track ball to move the PWD line to the RVOT and place the sample volume just proximal to the pulmonic valve. The sample volume should be at the same location where the RVOT diameter was measured. A doppler profile of the RVOT should be displayed with normal velocities in the RVOT. If a poor or low velocity doppler wave form is displayed reposition the view and move the PWD line thru out the RVOT. The PWD must be parallel to the RVOT jet to pick up the maximal velocity and obtain a good doppler wave form. After a good doppler wave form is obtained look at the morphology and the maximal velocity of the waveform and note it. Using the calipers feature, use the trackball and place the sample at the peak of the RVOT flow profile and note the velocity, which is the reference velocity.
Typically, the PWD of the RVOT will yield a maximum velocity less than 1 m/sec. Therefore, it's peak gradient is insignificant compared to the aortic valve peak velocity. In conclusion, it is entirely acceptable to not calculate the RVOT PWD peak velocity.