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Aortic Valve Area by Continuity Equation
Calcs>Aortic Stenosis>AVA by CE>1
Calculator
Severity
Mild
Mod
Severe
MeanAVG (mmHg)*
< 25
25-40
> 40
Mean AVG (mmHg)**
< 30
30-50
> 50
Vmax (m/sec)
2.6-3.0
3.0-4.0
> 4.0
AVA (cm2)
> 1.5
1.0-1.5
< 1.0
Indexed AVA (cm2/m2)
> 0.85
0.60-0.85
< 0.6
Velocity Ratio
< 2
2-4
> 4
Formula:
CSALVOT = 0.785
* DLVOT2
AVA = CSALVOT
* VTILVOT /
VTIAV
How
to get an AVA by Continuity Equation.
Step 1:
Measure the LVOT diameter in centimeters.
The optimal view is a maximally zoomed view
of the midesophageal AVLAX. The gain and compress
should be set so the endomyocardial wall of
the LVOT is clearly discernable. Freeze the
display and use the trackball to cycle thru
the cardiac cycle to the mid-ejection period
when the LVOT is at it's maximal diameter. Using
the calipers, measure from intimal wall to intimal
wall just proximal to the aortic valve. Activate
the Aortic Valve analysis package and select
LVOT diameter and enter the value of
the LVOT diameter.
Step
2: Obtain a continuous wave doppler of the
aortic valve. The optimal view is the deep
transgastric AVLAX view or the transgastric
AVLAX view. The former view is preferable if
obtainable. Once the view is obtained turn on
the CWD and use the track ball to move the CWD
line to the aortic valve. A doppler profile
of the aortic valve should be displayed with
high velocities in aortic 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.
Valvular aortic stenosis has a uniform increase
and decrease in the velocity profile.
Aortic Stenosis from IHSS has a dagger shaped
velocity profile. Using the tracing feature,
use the trackball and trace the doppler profile.
Activate the AV analysis package and select
V2 which is the velocity profile of the
aorta. Enter the value of the Aortic VTI or
V2.
Step
3: Obtain a pulse wave doppler of the LVOT.
The optimal view is the deep transgastric AVLAX view
or the transgastric AVLAX view. The former view is
preferable if obtainable. Once the view is obtained
turn on the PWD and use the track ball to move the
PWD line to the LVOT and place the sample volume just
proximal to the aortic valve. The sample volume should
be at the same location where the LVOT diameter was
measured. A doppler profile of the LVOT should be
displayed with normal velocities in the LVOT. If a
poor or low velocity doppler wave form is displayed
reposition the view and move the PWD line thru out
the LVOT. The PWD must be parallel to the LVOT 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 tracing
feature, use the trackball and trace the doppler profile.
Activate the AV analysis package and select V1
which is the velocity profile of the LVOT. Enter the
LVOT VTI or V1.
Step
3 (Optional): If you cannot obtain a good PWD
profile of the LVOT the CWD profile of the Aortic
Valve frequently will 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 LVOT.
This activity has been planned and implemented in accordance with the accreditation requirements and policies of the Accreditation Council for Continuing Medical Education through the joint providership of University of Nebraska Medical Center, Center for Continuing Education and JLS Interactive, LLC.
The University of Nebraska Medical Center, Center for Continuing Education is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.
This activity is approved by the American Society of Radiologic Technologists (ASRT) as sonography-related continuing education (CE). Credit(s) issued for successful completion of ASRT-approved CE activities are accepted by the American Registry of Diagnostic Medical Sonography, American Registry of Radiological Technologists, Cardiovascular Credentialing International and Canadian Association of Registered Diagnostic Ultrasound Professionals. Contact the applicable registry for additional information / restrictions on their acceptance of ASRT CE credit.