Flow-dependent changes in Doppler-derived aortic valve effective orifice area are real and not due to artifact.

OBJECTIVES We sought to determine whether the flow-dependent changes in Doppler-derived valve effective orifice area (EOA) are real or due to artifact. BACKGROUND It has frequently been reported that the EOA may vary with transvalvular flow in patients with aortic stenosis. However, the explanation of the flow dependence of EOA remains controversial and some studies have suggested that the EOA estimated by Doppler-echocardiography (EOA(Dop)) may underestimate the actual EOA at low flow rates. METHODS One bioprosthetic valve and three rigid orifices were tested in a mock flow circulation model over a wide range of flow rates. The EOA(Dop) was compared with reference values obtained using particle image velocimetry (EOA(PIV)). RESULTS There was excellent agreement between EOA(Dop) and EOA(PIV) (r2 = 0.94). For rigid orifices of 0.5 and 1.0 cm2, no significant change in the EOA was observed with increasing flow rate. However, substantial increases of both EOA(Dop) and EOA(PIV) were observed when stroke volume increased from 20 to 70 ml both in the 1.5 cm2 rigid orifice (+52% for EOA(Dop) and +54% for EOA(PIV)) and the bioprosthetic valve (+62% for EOA(Dop) and +63% for EOA(PIV)); such changes are explained either by the presence of unsteady effects at low flow rates and/or by an increase in valve leaflet opening. CONCLUSIONS The flow-dependent changes in EOA(Dop) are not artifacts but represent real changes in EOA attributable either to unsteady effects at low flow rates and/or to changes in valve leaflet opening. Such changes in EOA(Dop) can be relied on for clinical judgment making.

[1]  J. Nordrehaug,et al.  Factors affecting Doppler echocardiographic valve area assessment in aortic stenosis. , 1989, The American journal of cardiology.

[2]  Ronald Adrian,et al.  Optimization of particle image velocimeters , 1990, Other Conferences.

[3]  H Reul,et al.  Comparison of valvular resistance, stroke work loss, and Gorlin valve area for quantification of aortic stenosis. An in vitro study in a pulsatile aortic flow model. , 1995, Circulation.

[4]  R. Shandas,et al.  A method for determining the reference effective flow areas for mechanical heart valve prostheses: in vitro validation studies. , 2000, Circulation.

[5]  I. Palacios,et al.  Effects of dobutamine on Gorlin and continuity equation valve areas and valve resistance in valvular aortic stenosis. , 1992, The American journal of cardiology.

[6]  C Clark,et al.  The fluid mechanics of aortic stenosis - II. Unsteady flow experiments. , 1976, Journal of biomechanics.

[7]  Richard D. Keane,et al.  Optimization of particle image velocimeters. I, Double pulsed systems , 1990 .

[8]  M A García-Fernández,et al.  Flow dynamics of stenotic aortic valves assessed by signal processing of Doppler spectrograms. , 2000, The American journal of cardiology.

[9]  J. Chambers.  Low gradient, low ejection fraction aortic stenosis , 2003, Current treatment options in cardiovascular medicine.

[10]  N. Pandian,et al.  Variation of anatomic valve area during ejection in patients with valvular aortic stenosis evaluated by two-dimensional echocardiographic planimetry: comparison with traditional Doppler data. , 1998, Journal of the American College of Cardiology.

[11]  T. Lloyd.  Variation in Doppler-derived stenotic aortic valve area during ejection. , 1992, American heart journal.

[12]  K. Chan,et al.  Aortic valve area discrepancy by Gorlin equation and Doppler echocardiography continuity equation: relationship to flow in patients with valvular aortic stenosis. , 2000, The Canadian journal of cardiology.

[13]  C. Tribouilloy,et al.  Low‐Gradient Aortic Stenosis Operative Risk Stratification and Predictors for Long‐Term Outcome: A Multicenter Study Using Dobutamine Stress Hemodynamics , 2003, Circulation.

[14]  R. Shandas,et al.  Utility of the proximal jet width in the assessment of regurgitant and stenotic orifices--effect of low velocity filter and comparison to actual vena contracta width: an in vitro and numerical study. , 2000, European journal of echocardiography : the journal of the Working Group on Echocardiography of the European Society of Cardiology.

[15]  P. Pibarot,et al.  A new experimental method for the determination of the effective orifice area based on the acoustical source term , 2005 .

[16]  R. Shandas,et al.  Analysis of the effect of flow rate on the Doppler continuity equation for stenotic orifice area calculations: a numerical study. , 1998, Circulation.

[17]  R. Petitclerc,et al.  Simultaneous determination of aortic valve area by the Gorlin formula and by transesophageal echocardiography under different transvalvular flow conditions. Evidence that anatomic aortic valve area does not change with variations in flow in aortic stenosis. , 1997, Journal of the American College of Cardiology.

[18]  R. Shandas,et al.  In vitro measurement of the vena contracta for stenotic valves using laser induced fluorescence imaging and digital particle image velocimetry: comparison with ultrasound Doppler , 1996, Proceedings of 18th Annual International Conference of the IEEE Engineering in Medicine and Biology Society.

[19]  H. Schaff,et al.  Low-Output, Low-Gradient Aortic Stenosis in Patients With Depressed Left Ventricular Systolic Function: The Clinical Utility of the Dobutamine Challenge in the Catheterization Laboratory , 2002, Circulation.

[20]  M. S. Howe.  Theory of Vortex Sound , 2002 .

[21]  K. Karp,et al.  Flow dependence of the aortic valve area in patients with aortic stenosis: assessment by application of the continuity equation. , 1996, Journal of the American Society of Echocardiography : official publication of the American Society of Echocardiography.

[22]  E. Schwammenthal,et al.  Dobutamine echocardiography in patients with aortic stenosis and left ventricular dysfunction: predicting outcome as a function of management strategy. , 2001, Chest.

[23]  L. Lourenço.  Particle Image Velocimetry , 1989 .

[24]  C. Yancy,et al.  Usefulness of dobutamine echocardiography in distinguishing severe from nonsevere valvular aortic stenosis in patients with depressed left ventricular function and low transvalvular gradients. , 1995, The American journal of cardiology.

[25]  A. O. Borisyuk.  EXPERIMENTAL STUDY OF NOISE PRODUCED BY STEADY FLOW THROUGH A SIMULATED VASCULAR STENOSIS , 2002 .

[26]  R. Adrian.  Particle-Imaging Techniques for Experimental Fluid Mechanics , 1991 .

[27]  J. Tardif,et al.  Effects of variations in flow on aortic valve area in aortic stenosis based on in vivo planimetry of aortic valve area by multiplane transesophageal echocardiography. , 1995, The American journal of cardiology.

[28]  Physiologic Changes with Maximal Exercise in Asymptomatic Valvular Aortic Stenosis Assessed by Doppler Echocardiography , 1993 .

[29]  R. S. Mitchell,et al.  When should Doppler-determined valve area be better than the Gorlin formula?: Variation in hydraulic constants in low flow states. , 1987, Journal of the American College of Cardiology.

[30]  F P T Baaijens,et al.  A computational fluid-structure interaction analysis of a fiber-reinforced stentless aortic valve. , 2003, Journal of biomechanics.

[31]  E D Verrier,et al.  Dependence of Gorlin Formula and Continuit Equation Valve Areas on Transvalvular Volume Flow Rate in Valvular Aortic Stenosis , 1994, Circulation.

[32]  M. Crawford,et al.  Flow dependence of valve area in aortic stenosis: relation to valve morphology. , 1998, Journal of the American College of Cardiology.

[33]  A. Weyman,et al.  Variable effects of changes in flow rate through the aortic, pulmonary and mitral valves on valve area and flow velocity: impact on quantitative Doppler flow calculations. , 1985, Journal of the American College of Cardiology.

[34]  A. Powell.  Theory of Vortex Sound , 1964 .

[35]  M. Lighthill.  On sound generated aerodynamically I. General theory , 1952, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[36]  Markus Raffel,et al.  Particle Image Velocimetry: A Practical Guide , 2002 .

[37]  R. Pélissier,et al.  Ventricular flow Dynamic past Bileaflet Prosthetic Heart Valves , 1995, The International journal of artificial organs.

[38]  L. Badano,et al.  Changes in effective aortic valve area during ejection in adults with aortic stenosis. , 1996, The American journal of cardiology.

[39]  P. Pibarot,et al.  Comparison of valve resistance with effective orifice area regarding flow dependence. , 2001, The American journal of cardiology.

[40]  Damien Garcia,et al.  Estimation of aortic valve effective orifice area by Doppler echocardiography: effects of valve inflow shape and flow rate. , 2004, Journal of the American Society of Echocardiography : official publication of the American Society of Echocardiography.

[41]  J. Chambers,et al.  Continuity equation and Gorlin formula compared with directly observed orifice area in native and prosthetic aortic valves. , 1992, British heart journal.

[42]  E Sowton,et al.  Normal and stenotic human aortic valve opening: in vitro assessment of orifice area changes with flow. , 1990, European heart journal.

[43]  G. Batchelor,et al.  An Introduction to Fluid Dynamics , 1968 .

[44]  H T Low,et al.  Pulsatile flow studies of a porcine bioprosthetic aortic valve in vitro: PIV measurements and shear-induced blood damage. , 2001, Journal of biomechanics.

[45]  P. Pibarot,et al.  Independent contribution of left ventricular ejection time to the mean gradient in aortic stenosis. , 2002, The Journal of heart valve disease.

[46]  Michel L. Riethmuller,et al.  Extension of PIV to Super Resolution using PTV , 2001 .

[47]  Flow Dependence of Measures of Aortic Stenosis Severity During Exercise , 1995 .

[48]  J. Bermejo,et al.  Effects of dobutamine on Doppler echocardiographic indexes of aortic stenosis. , 1996, Journal of the American College of Cardiology.

[49]  R. deKemp,et al.  Temporal variations in effective orifice area during ejection in patients with valvular aortic stenosis. , 2003, Journal of the American Society of Echocardiography : official publication of the American Society of Echocardiography.