Automated flow rate calculations based on digital analysis of flow convergence proximal to regurgitant orifices

Noninvasive Cardiac Laboratory, Massachusetts General Hospital, Boston.

OBJECTIVES. The purpose of the study was to develop and validate an automated method for calculating regurgitant flow rate using color Doppler echocardiography. BACKGROUND. The proximal flow convergence method is a promising approach to quantitate valvular regurgitation noninvasively because it allows one to calculate regurgitant flow rate and regurgitant orifice area; however, defining the location of the regurgitant orifice is often difficult and can lead to significant error in the calculated flow rates. To overcome this problem we developed an automated algorithm to locate the orifice and calculate flow rate based on the digital Doppler velocity map. METHODS. This algorithm compares the observed velocities with the anticipated relative velocities, cos psi/2 pi r2. The orifice is localized as the point with maximal correlation between predicted and observed velocity, whereas flow rate is specified as the slope of the regression line. We validated this algorithm in an in vitro model for flow through circular orifices with planar surroundings and a porcine bioprosthesis. RESULTS. For flow through circular orifices, flow rates calculated on individual Doppler maps and on an average of eight velocity maps showed excellent agreement with true flow, with r = 0.977 and delta Q = -3.7 +/- 15.8 cm3/s and r = 0.991 and delta Q = -4.3 +/- 8.5 cm3/s, respectively. Calculated flow rates through the bioprosthesis correlated well but underestimated true flow, with r = 0.97, delta Q = -10.9 +/- 12.5 cm3/s, suggesting flow convergence over an angle > 2 pi. This systematic underestimation was corrected by assuming an effective convergence angle of 212 degrees. CONCLUSIONS. This algorithm accurately locates the regurgitant orifice and calculates regurgitant flow rate for circular orifices with planar surroundings. Automated analysis of the proximal flow field is also applicable to more physiologic surfaces surrounding the regurgitant orifice; however, the convergence angle should be adjusted. This automated algorithm should make quantification of regurgitant flow rate and regurgitant orifice area more reproducible and readily available in clinical cardiology practice.

This article has been cited by other articles:

				P. A. Grayburn and P. Bhella Grading Severity of Mitral Regurgitation by Echocardiography: Science or Art? J. Am. Coll. Cardiol. Img., March 1, 2010; 3(3): 244 - 246. [Full Text] [PDF]

				T. Buck, B. Plicht, P. Kahlert, I. M. Schenk, P. Hunold, and R. Erbel Effect of Dynamic Flow Rate and Orifice Area on Mitral Regurgitant Stroke Volume Quantification Using the Proximal Isovelocity Surface Area Method J. Am. Coll. Cardiol., August 26, 2008; 52(9): 767 - 778. [Abstract] [Full Text] [PDF]

				A Vitarelli, Y Conde, E Cimino, T Leone, I D'Angeli, S D'Orazio, and S Stellato Assessment of severity of mechanical prosthetic mitral regurgitation by transoesophageal echocardiography Heart, May 1, 2004; 90(5): 539 - 544. [Abstract] [Full Text] [PDF]

				J. D Thomas DOPPLER ECHOCARDIOGRAPHIC ASSESSMENT OF VALVAR REGURGITATION Heart, December 1, 2002; 88(6): 651 - 657. [Full Text] [PDF]

				M. Sitges, M. Jones, T. Shiota, D. L. Prior, J. X. Qin, H. Tsujino, F. Bauer, Y. J. Kim, D. Deserranno, N. L. Greenberg, et al. Interaliasing distance of the flow convergence surface for determining mitral regurgitant volume: a validation study in a chronic animal model J. Am. Coll. Cardiol., October 1, 2001; 38(4): 1195 - 1202. [Abstract] [Full Text] [PDF]

				R. Hoffmann and P. Hanrath Interaliasing distances to assess mitral regurgitation: dividing the rainbow of flow convergence J. Am. Coll. Cardiol., October 1, 2001; 38(4): 1203 - 1206. [Full Text] [PDF]

				N. L. Greenberg, P. M. Vandervoort, M. S. Firstenberg, M. J. Garcia, and J. D. Thomas Estimation of diastolic intraventricular pressure gradients by Doppler M-mode echocardiography Am J Physiol Heart Circ Physiol, June 1, 2001; 280(6): H2507 - H2515. [Abstract] [Full Text] [PDF]

				S. Bansal, D. Ehler, and J. L. Vacek Digital Echocardiography : Its Role in Modern Medical Practice Chest, January 1, 2001; 119(1): 271 - 276. [Abstract] [Full Text] [PDF]

				M. S. Firstenberg, P. M. Vandervoort, N. L. Greenberg, N. G. Smedira, P. M. McCarthy, M. J. Garcia, and J. D. Thomas Noninvasive estimation of transmitral pressure drop across the normal mitral valve in humans: importance of convective and inertial forces during left ventricular filling J. Am. Coll. Cardiol., November 15, 2000; 36(6): 1942 - 1949. [Abstract] [Full Text] [PDF]

				C. M. Tribouilloy, M. Enriquez-Sarano, K. R. Bailey, A. J. Tajik, and J. B. Seward Quantification of tricuspid regurgitation by measuring the width of the vena contracta with Doppler color flow imaging: a clinical study J. Am. Coll. Cardiol., August 1, 2000; 36(2): 472 - 478. [Abstract] [Full Text] [PDF]

				C. M. Tribouilloy, M. Enriquez-Sarano, S. L. Fett, K. R. Bailey, J. B. Seward, and A. J. Tajik Application of the proximal flow convergence method to calculate the effective regurgitant orifice area in aortic regurgitation J. Am. Coll. Cardiol., October 1, 1998; 32(4): 1032 - 1039. [Abstract] [Full Text] [PDF]

				D. Y. Leung, J. Wong, L. Rodriguez, M. Pu, P. M. Vandervoort, and J. D. Thomas Application of Color Doppler Flow Mapping to Calculate Orifice Area of St Jude Mitral Valve Circulation, September 22, 1998; 98(12): 1205 - 1211. [Abstract] [Full Text] [PDF]

				J. P. Sun, M. Pu, F. M. Fouad, R. Christian, W. J. Stewart, and J. D. Thomas Automated Cardiac Output Measurement by Spatiotemporal Integration of Color Doppler Data: In Vitro and Clinical Validation Circulation, February 18, 1997; 95(4): 932 - 939. [Abstract] [Full Text]

				S. A. Hall, M. E. Brickner, D. L. Willett, W. N. Irani, I. Afridi, and P. A. Grayburn Assessment of Mitral Regurgitation Severity by Doppler Color Flow Mapping of the Vena Contracta Circulation, February 4, 1997; 95(3): 636 - 642. [Abstract] [Full Text]

				P. A. Grayburn and R. M. Peshock Noninvasive Quantification of Valvular Regurgitation: Getting to the Core of the Matter Circulation, July 15, 1996; 94(2): 119 - 121. [Full Text]

				M. Enriquez-Sarano, L. J. Sinak, A. J. Tajik, K. R. Bailey, and J. B. Seward Changes in Effective Regurgitant Orifice Throughout Systole in Patients With Mitral Valve Prolapse : A Clinical Study Using the Proximal Isovelocity Surface Area Method Circulation, November 15, 1995; 92(10): 2951 - 2958. [Abstract] [Full Text]

				M. Pu, P. M. Vandervoort, B. P. Griffin, D. Y. Leung, W. J. Stewart, D. M. Cosgrove III, and J. D. Thomas Quantification of Mitral Regurgitation by the Proximal Convergence Method Using Transesophageal Echocardiography : Clinical Validation of a Geometric Correction for Proximal Flow Constraint Circulation, October 15, 1995; 92(8): 2169 - 2177. [Abstract] [Full Text]