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| Continuity
Equation: PVA = RVOT-VTI
* 0.785 * RVOTd2
/ PV-VTI |
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| How to
get an PVA by Continuity Equation. |
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| Step 1: 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. |
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| Step 2: Obtain
a RVOT diameter. The optimal view is
the RVIO view. Caliper the RVOT as close to
the valve as possible, in mid systole. |
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| Step 3: 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. |
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| Step
3 (Optional): If you cannot obtain a good PWD
profile of the LVOT the CWD profile of the Pulmonic
Valve may exhibit a ghost profile which
is contained in the CWD profile. This ghost profile
can be traced as if it was a PWD profile and entered
as the VTI of the RVOT. |
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