The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
Ian G Burwash - One of the best experts on this subject based on the ideXlab platform.
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Aortic valve area discrepancy by Gorlin equation and Doppler Echocardiography continuity equation: relationship to flow in patients with valvular aortic stenosis.
The Canadian journal of cardiology, 2000Co-Authors: Ian G Burwash, A Dickinson, R J Teskey, J W Tam, Kwan-leung ChanAbstract:BACKGROUND In vitro studies have shown a discrepancy between aortic valve area (AVA) measurements derived invasively by Gorlin equation (Gorlin AVA) and noninvasively by Doppler Echocardiography (Doppler-Echo) continuity equation (Doppler AVA) during low flow states. OBJECTIVE To assess whether a flow-related discrepancy between Gorlin AVA and Doppler AVA occurs in the clinical setting in patients with isolated valvular aortic stenosis. PATIENTS AND METHODS Seventy-five consecutive patients with isolated valvular aortic stenosis, who had AVA determined both invasively by Gorlin equation and noninvasively by Doppler-Echo continuity equation, were retrospectively reviewed. RESULTS Gorlin AVA and Doppler AVA correlated (r=0.68) over the narrow AVA range (Gorlin AVA 0.30 to 1.22 cm2); however, Doppler AVA was systematically larger than Gorlin AVA (0.80+/-0.21 versus 0.70+/-0.23 cm2, AVA difference = 0.10+/-0.17 cm2, P
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dependence of gorlin formula and continuity equation valve areas on transvalvular volume flow rate in valvular aortic stenosis
Circulation, 1994Co-Authors: Ian G Burwash, Alan S Pearlman, Carol D Kraft, Donald D Thomas, Mitsuaki Sadahiro, Edward D Verrier, Robert Thomas, Catherine M OttoAbstract:BACKGROUNDValve areas derived by the Gorlin formula have been observed to vary with transvalvular volume flow rate. Continuity equation valve areas calculated from Doppler-Echo data have become a widely used alternate index of stenosis severity, but it is unclear whether continuity equation valve areas also vary with volume flow rate. This study was designed to investigate the effects of changing transvalvular volume flow rate on aortic valve areas calculated using both the Gorlin formula and the continuity equation in a model of chronic valvular aortic stenosis.METHODS AND RESULTSUsing a canine model of chronic valvular aortic stenosis in which anatomy and hemodynamics are similar to those of degenerative aortic stenosis, each subject (n = 8) underwent three studies at 2-week intervals. In each study, transvalvular volume flow rates were altered with saline or dobutamine infusion (mean, 10.3 +/- 5.1 flow rates per study). Simultaneous measurements were made of hemodynamics using micromanometer-tipped cat...
Catherine M Otto - One of the best experts on this subject based on the ideXlab platform.
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dependence of gorlin formula and continuity equation valve areas on transvalvular volume flow rate in valvular aortic stenosis
Circulation, 1994Co-Authors: Ian G Burwash, Alan S Pearlman, Carol D Kraft, Donald D Thomas, Mitsuaki Sadahiro, Edward D Verrier, Robert Thomas, Catherine M OttoAbstract:BACKGROUNDValve areas derived by the Gorlin formula have been observed to vary with transvalvular volume flow rate. Continuity equation valve areas calculated from Doppler-Echo data have become a widely used alternate index of stenosis severity, but it is unclear whether continuity equation valve areas also vary with volume flow rate. This study was designed to investigate the effects of changing transvalvular volume flow rate on aortic valve areas calculated using both the Gorlin formula and the continuity equation in a model of chronic valvular aortic stenosis.METHODS AND RESULTSUsing a canine model of chronic valvular aortic stenosis in which anatomy and hemodynamics are similar to those of degenerative aortic stenosis, each subject (n = 8) underwent three studies at 2-week intervals. In each study, transvalvular volume flow rates were altered with saline or dobutamine infusion (mean, 10.3 +/- 5.1 flow rates per study). Simultaneous measurements were made of hemodynamics using micromanometer-tipped cat...
Sherif F. Nagueh - One of the best experts on this subject based on the ideXlab platform.
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Estimation of mean right atrial pressure using tissue Doppler imaging.
The American journal of cardiology, 1999Co-Authors: Maged F. Nageh, Helen A. Kopelen, William A. Zoghbi, Miguel A. Quinones, Sherif F. NaguehAbstract:Sixty-two patients underwent simultaneous right atrial pressure measurement and Doppler Echo including tissue Doppler to evaluate the utility of this technique in the estimation of right ventricular filling pressure. Mean right atrial pressure related weakly to the ratio of tricuspid peak early inflow velocity to annular early diastolic velocity (r = 0.75, p
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estimation of mean right atrial pressure using tissue Doppler imaging
American Journal of Cardiology, 1999Co-Authors: Maged F. Nageh, Helen A. Kopelen, William A. Zoghbi, Miguel A. Quinones, Sherif F. NaguehAbstract:Sixty-two patients underwent simultaneous right atrial pressure measurement and Doppler Echo including tissue Doppler to evaluate the utility of this technique in the estimation of right ventricular filling pressure. Mean right atrial pressure related weakly to the ratio of tricuspid peak early inflow velocity to annular early diastolic velocity (r = 0.75, p <0.0001), with a mean difference between Doppler and catheter pressures of 0.3 +/- 3.7 mm Hg.
Kwan-leung Chan - One of the best experts on this subject based on the ideXlab platform.
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Aortic valve area discrepancy by Gorlin equation and Doppler Echocardiography continuity equation: relationship to flow in patients with valvular aortic stenosis.
The Canadian journal of cardiology, 2000Co-Authors: Ian G Burwash, A Dickinson, R J Teskey, J W Tam, Kwan-leung ChanAbstract:BACKGROUND In vitro studies have shown a discrepancy between aortic valve area (AVA) measurements derived invasively by Gorlin equation (Gorlin AVA) and noninvasively by Doppler Echocardiography (Doppler-Echo) continuity equation (Doppler AVA) during low flow states. OBJECTIVE To assess whether a flow-related discrepancy between Gorlin AVA and Doppler AVA occurs in the clinical setting in patients with isolated valvular aortic stenosis. PATIENTS AND METHODS Seventy-five consecutive patients with isolated valvular aortic stenosis, who had AVA determined both invasively by Gorlin equation and noninvasively by Doppler-Echo continuity equation, were retrospectively reviewed. RESULTS Gorlin AVA and Doppler AVA correlated (r=0.68) over the narrow AVA range (Gorlin AVA 0.30 to 1.22 cm2); however, Doppler AVA was systematically larger than Gorlin AVA (0.80+/-0.21 versus 0.70+/-0.23 cm2, AVA difference = 0.10+/-0.17 cm2, P
Bertrand Chapron - One of the best experts on this subject based on the ideXlab platform.
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Low-Frequency Sea Surface Radar Doppler Echo
Remote Sensing, 2018Co-Authors: Yury Yu. Yurovsky, Vladimir Kudryavtsev, Semyon A. Grodsky, Bertrand ChapronAbstract:The sea surface normalized radar backscatter cross-section (NRCS) and Doppler velocity (DV) exhibit energy at low frequencies (LF) below the surface wave peak. These NRCS and DV variations are coherent and thus may produce a bias in the DV averaged over large footprints, which is important for interpretation of Doppler scatterometer measurements. To understand the origin of LF variations, the platform-borne Ka-band radar measurements with well-pronounced LF variations at frequencies below wave peak (0.19 Hz) are analyzed. These data show that the LF NRCS is coherent with wind speed at 21 m height while the LF DV is not. The NRCS-wind correlation is significant only at frequencies below 0.01 Hz indicating either differences between near-surface wind (affecting radar signal) and 21-m height wind (actually measured) or contributions of other mechanisms of LF radar signal variations. It is shown that non-linearity in NRCS-wave slope Modulation Transfer Function (MTF) and inherent averaging within radar footprint account for NRCS and DV LF variance, with the exception of VV NRCS for which almost half of the LF variance is unexplainable by these mechanisms and perhaps attributable to wind fluctuations. Although the distribution of radar DV is quasi-Gaussian, suggesting virtually little impact of non-linearity, the LF DV variations arise due to footprint averaging of correlated local DV and non-linear NRCS. Numerical simulations demonstrate that MTF non-linearity weakly affects traditional linear MTF estimate (less than 10% for typical MTF magnitudes less than 20). Thus the linear MTF is a good approximation to evaluate the DV averaged over large footprints typical of satellite observations.
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Low-Frequency Sea Surface Radar Doppler Echo
2018Co-Authors: Yury Yu. Yurovsky, Vladimir Kudryavtsev, Semyon A. Grodsky, Bertrand ChapronAbstract:Observed sea surface Ka-band normalized radar backscatter cross section (NRCS) and Doppler velocity (DV) exhibit energy at low frequencies (LF) below the surface wave range. It is shown that non-linearity in NRCS-wave slope Modulation Transfer Function (MTF) and inherent NRCS averaging within the footprint account for the NRCS and DV LF variance with the exception of VV NRCS for which almost half of the LF variance is attributable to wind fluctuations. Although the distribution of radar DV is quasi-Gaussian suggesting virtually little impact of non-linearity, the LF DV variations arise due to footprint averaging of correlated local DV and non-linear NRCS. Numerical simulations demonstrate that MTF non-linearity weakly affects traditional linear MTF estimate (less than 10% for |MTF|< 20). Thus the linear MTF is a good approximation to evaluate the DV averaged over large footprints typical of satellite observations.