aortic stenosis mason

8/14/2019 Aortic Stenosis Mason

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Daniel W Mason MD FACC FASE


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EchocardiographyCurrently, TTE and occasionally TEE are

the diagnostic tools most commonly used toevaluate the AV, with visualization of theleaflets, evaluate the other valves, look at theright side and estimate pressures, look at theaorta, quantitate the degree of stenosis, andevaluate lv function.


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ImagingNot talked about very much, but still very

important. The majority of times we can seeleaflet thickening, calcification, and restriction.

In congenital AS you may see good leafletmobility and still have significant AS as much ofthe stenosis is just at the orifice and the leafletsmay be pliable.

But in adults if you see the leaflets movingwell, you wont have much stenosis, ie you canrule it out on appearance alone many times.Quantification is more difficult, but always make a

guess just based on appearance. It is reassuring ifit matches do ler data.


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PlanemetryThe simplest way to get a valve area, but

you need a good window, a good short axis

view, and it helps to not have much calciumwhich will give side lobe artifacts. TEE canreally help here.


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FORMULASR 2 = area of circle

R2 =

(1/2D)2

= 1/4D2

= 0.785D2

Area of circle = 0.785D2


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FORMULASArea x Length = Volume

L


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FORMULASIf flow through a cylinder were constant,

we can easily measure volume if we know

velocity, time, and diameter.


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FORMULAS

L = V x T

V

T


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FORMULASBut flow is not constant, its velocity is

constantly changing, so how can we

measure volume. What would Sir Isaac

Newton have done? Calculus? Integrate?


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VTIV

a

T


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VTIThe integral of the curve in essence is takingthe average velocity during that time, andmultiplying it by the time of the systolicperiod, giving us stroke distance.


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MORE FORMULASAVA x TVIav = Arealvot x TVIlvot

AVA = Arealvot x (TVIlvot/ TVIav)

Using Maximal velocities of the aorticvalve and lvot gives a reasonable

approximation of the area.

Ratios of TVIs or maximal velocities(DOI) are most helpful when it is

difficult to measure a diameter

(calcium or prosthesis)


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Major Sources of ErrorAlignment of the transducer

Accurate measurements

Atrial fibPositioning of the PW sampling volume.

Confusion with mitral regurgitation

Confusion with HOCM


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LVOT diameter vs AVA (DOI 0.3)1.8 cm 0.76 cm2

2.0 cm 0.94 cm2

2.2 cm 1.14 cm2

2.4 cm 1.4 cm2


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So always look to see that the numbersmake sense. Look at the LVOTd, the LVOTTVI,

and the gradient. Be familiar with normalvalues. A quick check for lvot dimension is tocompare the DOI with the AVA.

Another useful check is to look at leftventricular function and compare it to the lvot

TVI and max V.

Finally, compare your gradients and valve

areas with the appearance of the valve and besure you are comfortable with it.

If not sure, make it clear there isuncertainty in the report.


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LV DysfunctionThis is a risk factor but does not precludea surgical approach. Pseudo-stenosis issecondary to a poor cardiac output, so that

mild to moderate stenosis may calculate tobe severe. (I think of it as a weak ventriclethat cant open a stiff valve ).

Poor LV reserve suggest increased risk,

but is also not an absolute contraindication.Dobutamine helps us define this. Goodreserve usually means the LVOTtvi will increase

at least 20% with dobutamine.


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