The SV has multiple ways it can be measured. There are 2 main divisions - Using the end systolic (ESV) and end diastolic volumes (EDV) OR by looking at the left ventricular outflow tract (LVOT) flow.
Methods
SV= EDV-ESV. - this is the default method EncaptureMD uses.
SV can also be calculated using the LVOT and flow into the aorta
SV =pi*( LVOT^2)/4 * VTI
EncaptureMD is calculating the SV based on the ESV and EDV. In addition, we are using the most accurate ESV and EDV. In the image below, the chosen ESV and EDV are the most accurate methods from the numbers above. The order of accuracy is
Least accurate
- Teichholz
- 4 and 2 chamber Simpson's
- Biplane Simpson's
Most accurate
The most accurate method then becomes the chosen values (1 and 2) which is then used to calculate the SV, CO, CI, and EF (3).
The US machine can send multiple SV values:
The Cube method value is so inaccurate, we do not even include it. The others correspond to the methods above. If the customer wants to use the SV from LVOT, then we have to disable the calculation of EDV-ESV and then map the SV to the Stroke Volume, Left Ventricle, Left Ventricular Outflow Tract measurement in the EncaptureMD mapper. Both steps must be done.