1/14
GUH - Echo Tweetorial - Aortic Stenosis:
How do they calculate:
1. Valve area
2. Mean AV gradient
3. Max AV gradient
2/14
Essential Principles:
1. The effective orifice area is always smaller than the anatomical orifice area
This effective orifice area is what is calculated
It is the key determinant of survival
2. Continuity equation
Conservation of mass
3/14
Continuity equation:
A2 X V2 = A1 x V1
(AVA) x (AV VTI) = (LVOT CSA) x (LVOT VTI)
AVA = [(LVOT CSA) x (LVOT VTI)]/ AV VTI
4/14
We need to measure 3 of 4 variables
The 4th is unknown and is the AV effective orifice area
A1: LVOT cross sectional area
Measure at level of cusp insertion
Inner edge to inner edge
Mid systole
5/14
Measuring V1 - LVOT VTI
6/14
LVOT VTI
Pulse wave doppler!
Remember - Shave the whiskers!
7/14
And lastly measure V2: AV VTI
Continous wave doppler!
Tracing the doppler envelope also calculates Mean and Max gradients using the simplified Bernoulli Equation
8/14
And to explain:
9/14
How can you make sure you have the seen the maximum gradient?
1. Focused AV 5ch view
2. Right parasternal view
10/14
Focused AV 5ch:
Slide probe laterally, in the same ribspace - towards the axilla to line up the cursor
11/14
Right parasternal:
1. Lie the patient in the RIGHT lateral position
2. Obtain standard PLAX view in right lateral position
3. Follow the path of the ascending aorta across the sternum
4. Rock medially + tail up
Probe now faces down the ascending aorta through the AV
12/14
Once Identified - use the pedoff probe to assess
Tricky to learn but worth the effort!
13/14
Here is the doppler envelope acquired!
14/14
Hope this was informative
Next time - on GUH tweetorials:
Assessment of volume status!
#echofirst @drjimday @cianmcdermott @AndyNeill @iceman_ex @cmc47802929 @POCUSClub @GoughCJ @geoghep @BioengineerGUH @cmc47802929
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