CORRESPONDENCE
Pressure recovery and aortic stenosis
Curt G. DeGroff, MDa,
Robin Shandas, PhDa and
Lilliam Valdes-Cruz, MDa
a Cardiac Care Center, The Children’s Hospital, University of Colorado HSC, 1056 East 19th Avenue, Denver, Colorado 80218, USA
Regarding the recent article by Baumgartner et al. (1), we commend the authors for their efforts in predicting pressure recovery from the following variables: 1) calculated dynamic pressure, 2) estimated effective orifice area, and 3) estimated cross-sectional area of the ascending aorta. However, we have several concerns.
The declaration that, "Although pressure recovery has also been demonstrated in experimental ... and in clinical studies ... of native aortic stenosis, this phenomenon has not been recognized as a source of discrepancy between Doppler and catheter gradients across stenosed aortic valves" disregards several important studies and commentaries that have been published on this subject (2–11). Curiously, several of these studies were cited by Baumgartner et al. (1), and several were published by the same group.
In addition, we believe the effects of nonsimultaneous recordings (Doppler vs. catheter gradients) were unjustifiably trivialized by Baumgartner et al. (1). Other sources of error not mentioned include the effects from fluid-filled catheters (e.g., damping) and problems associated with measuring dynamic versus static pressure (10). Lastly, the sensitivity of the equation (2) to errors commonly found in determining the dependent variables (dynamic pressure, effective orifice area and cross-sectional area of the aorta) needs to be addressed.
In summary, the article by Baumgartner et al. (1) should have included more information on previous data regarding the discrepancy between Doppler and catheter gradients across stenotic aortic valves. We do agree that more clinical studies like these are needed, especially in children (11). Most likely, the reluctance to report such data is related to the fact that it is difficult to accurately locate and measure the precise point of pressure recovery using a standard catheter in the clinical setting.
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References
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- Baumgartner H, Stefenelli T, Niederberger J, Schima H, Maurer G. "Overestimation" of catheter gradients by Doppler ultrasound in patients with aortic stenosis: a predictable manifestation of pressure recovery. J Am Coll Cardiol. 1999;33:1655–1661[Abstract/Free Full Text]
- Levine RA, Jimoh A, Cape EG, McMillan S, Yoganathan AP, Weyman AE. Pressure recovery distal to a stenosis: potential cause of gradient "overestimation" by Doppler echocardiography. J Am Coll Cardiol. 1989;13:706–715[Abstract]
- Yoganathan AP, Valdes-Cruz LM, Schmidt-Dohna J, et al. Continuous wave Doppler velocities and gradients across fixed tunnel obstructions: studies in vitro and in vivo. Circulation. 1987;76:657–666[Abstract/Free Full Text]
- Cape EG, Jones M, Yamada I, VanAuker MD, Valdes-Cruz LM. Turbulent/viscous interactions control Doppler/catheter pressure discrepancies in aortic stenosis: the role of the Reynolds number. Circulation. 1996;94:2975–2981[Abstract/Free Full Text]
- Baumgartner H, Schima H, Tulzer G, Kuhn P. Effect of stenosis geometry on the Doppler-catheter gradient relation in vitro: a manifestation of pressure recovery. J Am Coll Cardiol. 1993;21:1018–1025[Abstract]
- Voelker W, Reul H, Stelzer T, Schmidt A, Karsch KR. Pressure recovery in aortic stenosis: an in vitro study in a pulsatile flow model. J Am Coll Cardiol. 1992;20:1585–1593[Abstract]
- Levine RA, Cape EG, Yoganathan AP. Pressure recovery distal to stenoses: expanding clinical applications of engineering principles. J Am Coll Cardiol. 1993;21:1026–1028[Medline]
- Niederberger J, Schima H, Maurer G, Baumgartner H. Importance of pressure recovery for the assessment of aortic stenosis by Doppler ultrasound: role of aortic size, aortic valve area, and direction of the stenotic jet in vitro. Circulation. 1996;94:1934–1940[Abstract/Free Full Text]
- DeGroff CG. Valdez-Cruz LM, Cayre R. Doppler ultrasound in cardiology. Echocardiography in Congenital Heart Disease: Embryologic-Anatomic Considerations and Surgical Implications. New York: Lippincott-Raven; 1999.
- Chambers T. Is pressure recovery an important cause of "Doppler aortic stenosis" with no gradient at cardiac catheterisation? Heart. 1996;76:381–383[Free Full Text]
- Lemler MS, Valdes-Cruz LM, Shandas R, Cape EG. Insights into catheter/Doppler discrepancies: a clinical study of congenital aortic stenosis. Am J Cardiol. 1999;83:1447–1450[Medline]
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