| Parameter | Normal | Mild | Moderate | Severe |
|---|---|---|---|---|
<2.5 | 2.6-2.9 | 3-4 | >4 | |
<16 | <36 | 36-64 | >65 | |
25 | <20 | 20-40 | >40 | |
>2.5 | >1.5 | 1-1.5 | <1 | |
n/a | >0.85 | 0.6-0.85 | <0.6 | |
n/a | >0.5 | 0.25-0.5 | <0.25 |
Aortic Valve Area by the Continuity Equation
- Equation states that the net forward flow SV through any part of the heart should be the same (dependent on there not being any shunts or abnormal anatomy)
- SV LVOT = SV AV
- SV = CSA x VTI (VTI = the area bounded by the spectral doppler velocity-time curve)
- CSA AV x VTI AV = CSA LVOT x VTI LVOT,
- then rearrange so CSA AV = CSA LVOT x VTI LVOT / VTI AV
Dimensionless Index
Velocity LVOT / Velocity AV
Ratio should be close to 1 i.e. there should be minimal difference between the two suggesting there is no obstruction causing an increase in velocity
A useful metric as it accounts for ow LVEF, measurement errors of the LVOT or AV dimensions as well as alignment errors as the ratio should remain fixed.