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Published on: February 22, 2018
Revisiting the simplified bernoulli equation
Jeffrey J Heys1, Nicole Holyoak, Anna M Calleja
1Department of Chemical and Biological Engineering, Montana State University - Bozeman, Box 173920, Bozeman, MT 59717, USA.
Insights
Computational fluid dynamics (CFD) shows promise for assessing aortic valve stenosis severity. CFD analysis of echocardiography data offers improved accuracy over the simplified Bernoulli equation, especially in severe cases.
Area of Science:
- Cardiovascular Research
- Biomedical Engineering
- Fluid Dynamics
Background:
- Aortic valve stenosis severity is assessed via invasive catheterization or non-invasive Doppler Echocardiography with the simplified Bernoulli equation.
- Catheterization is more accurate but carries higher complication risks.
Purpose of the Study:
- To investigate computational fluid dynamics (CFD) as an alternative method for analyzing echocardiography data.
- To determine if CFD can yield results comparable to invasive catheterization measurements.
Main Methods:
- An in vitro heart model with a rigid orifice was utilized.
- Echocardiographic data was analyzed using both the simplified Bernoulli equation and CFD (Navier-Stokes equations).
- Results were compared against experimental catheterization data.
Main Results:
- For a 0.93cm² orifice, CFD and the simplified Bernoulli equation showed no significant difference from catheterization (p > 0.01).
- For a smaller 0.52cm² orifice, CFD demonstrated better agreement with experimental data than the simplified Bernoulli equation (p < 0.01).
Conclusions:
- In this in vitro model, CFD improves upon the simplified Bernoulli equation for assessing aortic valve stenosis.
- The most significant improvements with CFD were observed at higher levels of valvular stenosis.
Background:
The assessment of the severity of aortic valve stenosis is done by either invasive catheterization or non-invasive Doppler Echocardiography in conjunction with the simplified Bernoulli equation. The catheter measurement is generally considered more accurate, but the procedure is also more likely to have dangerous complications.
Objective:
The focus here is on examining computational fluid dynamics as an alternative method for analyzing the echo data and determining whether it can provide results similar to the catheter measurement.
Methods:
An in vitro heart model with a rigid orifice is used as a first step in comparing echocardiographic data, which uses the simplified Bernoulli equation, catheterization, and echocardiographic data, which uses computational fluid dynamics (i.e., the Navier-Stokes equations).
Results:
For a 0.93cm(2) orifice, the maximum pressure gradient predicted by either the simplified Bernoulli equation or computational fluid dynamics was not significantly different from the experimental catheter measurement (p > 0.01). For a smaller 0.52cm(2) orifice, there was a small but significant difference (p < 0.01) between the simplified Bernoulli equation and the computational fluid dynamics simulation, with the computational fluid dynamics simulation giving better agreement with experimental data for some turbulence models.
Conclusion:
For this simplified, in vitro system, the use of computational fluid dynamics provides an improvement over the simplified Bernoulli equation with the biggest improvement being seen at higher valvular stenosis levels.
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