Simultaneous Doppler/catheter measurements of pressure gradients in aortic valve disease: a correction to the Bernoulli equation based on velocity decay in the stenotic jet.
OBJECTIVE
Characterization of the severity of a stenotic aortic valve relies on accurate measurement of the pressure drop across the valve. A simplified form of the Bernoulli equation has been used to estimate pressure drops using Doppler ultrasound, but these measurements often overestimate gold standard measurements performed during cardiac catheterization. Sources of discrepancy between the Doppler and catheter measurements have been identified, but no method has been developed to fully reconcile the two techniques.


METHODS
In this study we developed a correction to the clinical form of the Bernoulli equation based on receiving chamber geometry and turbulent jet profiles. The theoretical treatment of the mechanical energy balance, assuming a shape to the stenotic jet profile is described, and the assumptions in our model are discussed. The use of the model was then demonstrated in an in vivo clinical study in which simultaneous Doppler and catheter data were obtained.


RESULTS
Discrepancies between Doppler and catheter are shown to be a function of the predicted pressure recovery location based on our assumed profile. There exists a distance of about 8.67 valve radii downstream where agreement in peak pressure gradients is theoretically achieved.


CONCLUSIONS
The results demonstrate the ability to characterize pressure recovery distal to the valve. Our approach, to substitute a more appropriate velocity profile into the mechanical energy balance, unifies geometric parameters and the physics of turbulent jet flow in an equation involving quantities already routinely measured in an echocardiographic examination of aortic stenosis. This allows for both the maximal and recovered pressure gradient to be obtained from the Doppler data. These results have implications for optimal pressure sensor placement for the assessment of aortic stenosis and also for the evaluation of prosthetic heart valves in vitro.
VanAuker
M D
MD
Division of Cardiology, Brookdale University Hospital and Medical Center, Brooklyn, New York 11212, USA.
Hla
A
A
Meisner
J S
JS
Strom
J A
JA
D001021:Aortic Valve / Q000000981:diagnostic imaging / Q000503:physiopathology; D001024:Aortic Valve Stenosis / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery; D001705:Bioprosthesis; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D006328:Cardiac Catheterization; D015150:Echocardiography, Doppler; D019544:Equipment Failure Analysis; D019918:Heart Valve Prosthesis Implantation; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D011183:Postoperative Complications / Q000000981:diagnostic imaging / Q000503:physiopathology; D011237:Predictive Value of Tests