When should Doppler-determined valve area be better than the Gorlin formula?: Variation in hydraulic constants in low flow states

In low flow states, underestimation errors occur when the Gorlin formula is used to calculate valve area. A model of valvular stenosis designed to examine changes in the hydraulic discharge coefficient (Cd) and coefficient of orifice contraction (Cc) may explain these errors. Unsteady flow was examined in a pulsatile pump model and in a dog model. Valve areas were calculated from pressure and flow data using: a modified form of the Gorlin formula (assuming constant values for Cd and Cc) and a corrected formula (with values of Cd and Cc obtained from steady state data). Valve area was also calculated using the continuity equation with velocity and flow data (constant Cc). Flow velocities were measured using a newly designed ultrasound Doppler catheter capable of resolving flow velocities of up to 5.5 m/s. Both the corrected formula and continuity equation were highly predictive of actual valve area (r = 0.99, slope or M = 0.96 and r = 0.99, M = 1.06, respectively). The modified Gorlin equation was less accurate and tended to underestimate valve areas (r = 0.87, M = 0.83). This underestimation was most notable at low rates of flow (Gorlin: r = 0.94, M = 0.53; continuity: r = 0.93, M = 0.81 and r = 0.94, M = 0.89, respectively) more accurately than the modified Gorlin formula (r = 0.69, M = 0.49). In patients with low cardiac output, hemodynamic formulas, such as the Gorlin formula, which assume a constant value for the hydraulic discharge coefficient (Cd), may be less accurate than formulas using either a corrected value of Cd or Doppler-determined flow velocity and mean systolic flow.

This article has been cited by other articles:

				I G Burwash, M Lortie, P Pibarot, R A de Kemp, S Graf, G Mundigler, A Khorsand, C Blais, H Baumgartner, J G Dumesnil, et al. Myocardial blood flow in patients with low-flow, low-gradient aortic stenosis: differences between true and pseudo-severe aortic stenosis. Results from the multicentre TOPAS (Truly or Pseudo-Severe Aortic Stenosis) study Heart, December 1, 2008; 94(12): 1627 - 1633. [Abstract] [Full Text] [PDF]

				J. Mascherbauer, C. Fuchs, M. Stoiber, H. Schima, E. Pernicka, G. Maurer, and H. Baumgartner Systemic pressure does not directly affect pressure gradient and valve area estimates in aortic stenosis in vitro Eur. Heart J., August 2, 2008; 29(16): 2049 - 2057. [Abstract] [Full Text] [PDF]

				S. H Little, K.-L. Chan, and I. G Burwash Impact of blood pressure on the Doppler echocardiographic assessment of severity of aortic stenosis Heart, July 1, 2007; 93(7): 848 - 855. [Abstract] [Full Text] [PDF]

				S. Goland, A. Trento, K. Iida, L. S C Czer, M. De Robertis, T. Z Naqvi, K. Tolstrup, T. Akima, H. Luo, and R. J Siegel Assessment of aortic stenosis by three-dimensional echocardiography: an accurate and novel approach Heart, July 1, 2007; 93(7): 801 - 807. [Abstract] [Full Text] [PDF]

				J Bermejo and R Yotti Low-gradient aortic valve stenosis: value and limitations of dobutamine stress testing Heart, March 1, 2007; 93(3): 298 - 302. [Abstract] [Full Text] [PDF]

				L. Kadem, R. Rieu, J. G. Dumesnil, L.-G. Durand, and P. Pibarot Flow-Dependent Changes in Doppler-Derived Aortic Valve Effective Orifice Area Are Real and Not Due to Artifact J. Am. Coll. Cardiol., January 3, 2006; 47(1): 131 - 137. [Abstract] [Full Text] [PDF]

				L. Kadem, R. Rieu, J. G. Dumesnil, L.-G. Durand, and P. Pibarot Flow-Dependent Changes in Doppler-Derived Aortic Valve Effective Orifice Area Are Real and Not Due to Artifact J. Am. Coll. Cardiol., December 14, 2005; (2005) j.jacc.2005.05.100v1. [Abstract] [Full Text] [PDF]

				C Kupfahl, M Honold, G Meinhardt, H Vogelsberg, A Wagner, H Mahrholdt, and U Sechtem Evaluation of aortic stenosis by cardiovascular magnetic resonance imaging: comparison with established routine clinical techniques Heart, August 1, 2004; 90(8): 893 - 901. [Abstract] [Full Text] [PDF]

				G. Reis, M. S. Motta, M. M. Barbosa, W. A. Esteves, S. F. Souza, and E. A. Bocchi Dobutamine stress echocardiography for noninvasive assessment and risk stratification of patients with rheumatic mitral stenosis J. Am. Coll. Cardiol., February 4, 2004; 43(3): 393 - 401. [Abstract] [Full Text] [PDF]

				D. Gilon, E. G. Cape, M. D. Handschumacher, J.-K. Song, J. Solheim, M. VanAuker, M. E. E. King, and R. A. Levine Effect of three-dimensional valve shape on the hemodynamics of aortic stenosis: Three-dimensional echocardiographic stereolithography and patient studies J. Am. Coll. Cardiol., October 16, 2002; 40(8): 1479 - 1486. [Abstract] [Full Text] [PDF]

				Y J Kim, M Jones, T Shiota, H Tsujino, J X Qin, F Bauer, M Sitges, J Kwan, L A Cardon, A D Zetts, et al. Effect of load alterations on the effective regurgitant orifice area in chronic aortic regurgitation Heart, October 1, 2002; 88(4): 397 - 400. [Abstract] [Full Text] [PDF]

				P. A. Grayburn and E. J. Eichhorn Dobutamine Challenge for Low-Gradient Aortic Stenosis Circulation, August 13, 2002; 106(7): 763 - 765. [Full Text] [PDF]

				E. Schwammenthal, Z. Vered, Y. Moshkowitz, B. Rabinowitz, Z. Ziskind, A. K. Smolinski, and M. S. Feinberg Dobutamine Echocardiography in Patients With Aortic Stenosis and Left Ventricular Dysfunction : Predicting Outcome as a Function of Management Strategy Chest, June 1, 2001; 119(6): 1766 - 1777. [Abstract] [Full Text] [PDF]

				S Takeda, H Rimington, and J Chambers The relation between transaortic pressure difference and flow during dobutamine stress echocardiography in patients with aortic stenosis Heart, July 1, 1999; 82(1): 11 - 14. [Abstract] [Full Text] [PDF]

				M. Arsenault, N. Masani, G. Magni, J. Yao, L. Deras, and N. Pandian Variation of anatomic valve area during ejection in patients with valvular aortic stenosis evaluated by two-dimensional echocardiographic planimetry: comparison with traditional Doppler data J. Am. Coll. Cardiol., December 1, 1998; 32(7): 1931 - 1937. [Abstract] [Full Text] [PDF]

				C. G. DeGroff, R. Shandas, and L. Valdes-Cruz Analysis of the Effect of Flow Rate on the Doppler Continuity Equation for Stenotic Orifice Area Calculations : A Numerical Study Circulation, April 28, 1998; 97(16): 1597 - 1605. [Abstract] [Full Text] [PDF]

				D. Gilon, E. G. Cape, M. D. Handschumacher, L. Jiang, C. Sears, J. Solheim, E. Morris, J. T. Strobel, S. M. Miller-Jones, A. E. Weyman, et al. Insights From Three-dimensional Echocardiographic Laser Stereolithography: Effect of Leaflet Funnel Geometry on the Coefficient of Orifice Contraction, Pressure Loss, and the Gorlin Formula in Mitral Stenosis Circulation, August 1, 1996; 94(3): 452 - 459. [Abstract] [Full Text]

				W. Voelker, H. Reul, G. N. Ing, T. S. Ing, B. S. Ing, A. S. Ing, and K. R. Karsch 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 Circulation, February 15, 1995; 91(4): 1196 - 1204. [Abstract] [Full Text]

				A. D. Waggoner, B. Barzilai, and J. E. Perez Two-Dimensional Doppler Echocardiographic Derived Aortic Valve Area in Aortic Stenosis Journal of Diagnostic Medical Sonography, March 1, 1991; 7(2): 64 - 72. [Abstract] [PDF]