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Estimation of Mitral Regurgitation with a Hemielliptic Curve-Fitting Algorithm: In Vitro Experiments with Native Mitral Valves Joanne Hopmeyer, PhD, Shengqui He, MD, Kristen M. Thorvig, Ellen McNeil, BS, Patrick W. Wilkerson, BS, Robert A. Levine, MD, FACC, Ajit P. Yoganathan, PhD Journal of the American Society of Echocardiography Volume 11, Issue 4, Pages (April 1998) DOI: /S (98) Copyright © 1998 American Society of Echocardiogryaphy Terms and Conditions
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Fig. 1 Schematic of the in vitro model. Native mitral valves were mounted in the model, which also incorporated an aorta of physiologic dimensions. Journal of the American Society of Echocardiography , DOI: ( /S (98) ) Copyright © 1998 American Society of Echocardiogryaphy Terms and Conditions
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Fig. 2 Schematic of the mounted mitral valve illustrating the attachment of the valve annulus to the annular ring and the papillary muscles to the rods. Journal of the American Society of Echocardiography , DOI: ( /S (98) ) Copyright © 1998 American Society of Echocardiogryaphy Terms and Conditions
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Fig. 3 Schematic of the pulsatile flow loop used for the in vitro studies. This system was able to mimic a wide range of physiologic conditions and was used to simulate a heart rate of 70 beats/min and cardiac outputs between 2 and 6 L/min. Journal of the American Society of Echocardiography , DOI: ( /S (98) ) Copyright © 1998 American Society of Echocardiogryaphy Terms and Conditions
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Fig. 4 Flow chart of the curve-fitting algorithm that was used for the analysis of the digitized two-dimensional images. In each image, the color information was converted to velocity and isovelocity curves were recreated from the data. The dimensions A, B, and C necessary to make the hemielliptic calculations were obtained by fitting hemielliptic curves to the data. Flow rates calculated by the hemielliptic and hemispheric formulas were compared with the true flow rates. Journal of the American Society of Echocardiography , DOI: ( /S (98) ) Copyright © 1998 American Society of Echocardiogryaphy Terms and Conditions
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Fig. 5 Typical flow waveforms measured through the aortic and mitral valves by flowmeters. During diastole, the mitral valve opens and the ventricular chamber fills through the mitral valve. At this time, the aortic valve is closed and no flow is detected through the aorta. During systole, flow exits the ventricular chamber through both the aorta and the regurgitant mitral valve. Journal of the American Society of Echocardiography , DOI: ( /S (98) ) Copyright © 1998 American Society of Echocardiogryaphy Terms and Conditions
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Fig. 6 Calculated flow rates by the hemispheric and hemielliptic formulas from color Doppler images are plotted as a function of the isovelocity for a range of isovelocity contours and are compared with the true flow rate for a range of peak regurgitant flow rates. The true flow rate of 16 L/min is indicated by the horizontal line. Journal of the American Society of Echocardiography , DOI: ( /S (98) ) Copyright © 1998 American Society of Echocardiogryaphy Terms and Conditions
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Fig. 7 Regression analysis was used to demonstrate the accuracy of the hemielliptic formula in estimating the true regurgitant flow rate. Good agreement was obtained between the true and calculated flow rates (y = 1.02 x ; r = 0.91). Journal of the American Society of Echocardiography , DOI: ( /S (98) ) Copyright © 1998 American Society of Echocardiogryaphy Terms and Conditions
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Fig. 8 Bland-Altman analysis indicating the error in measurement between the true flow rate measured by flowmeter and calculated flow rates with the hemielliptic formula applied to color Doppler images. The error in the measurements was small compared with the range of flow rates studied with a mean error 0.5 ± 1.17 L/min. Journal of the American Society of Echocardiography , DOI: ( /S (98) ) Copyright © 1998 American Society of Echocardiogryaphy Terms and Conditions
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Fig. 9 Regression analysis of hemispheric formula between the calculated flow rate compared with the true flow rate. Large errors were evident, as indicated by the regression slope and intercept and by the poor regression coefficient (y = 1.18 x –2.2; r = 0.66). Journal of the American Society of Echocardiography , DOI: ( /S (98) ) Copyright © 1998 American Society of Echocardiogryaphy Terms and Conditions
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Fig. 10 Bland-Altman analysis of the hemispheric formula demonstrating the wide range of error between the true and calculated flow rates. There was a significant range in the error in the measurements, with a mean error of 0.13 ± 3.38 L/min. Journal of the American Society of Echocardiography , DOI: ( /S (98) ) Copyright © 1998 American Society of Echocardiogryaphy Terms and Conditions
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