European Journal of Echocardiography Advance Access originally published online on February 19, 2008
European Journal of Echocardiography 2008 9(3):321; doi:10.1093/ejechocard/jen037
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Determination of stenotic mitral valve area: new, old, and gold standards
Med.Klinik 2
University of Erlangen
Ulmenweg 18
91054 Erlangen
Germany
Med.Klinik 2
University of Erlangen
Ulmenweg 18
91054 Erlangen
Germany
E-mail address: frank.flachskampf{at}uk-erlangen.de
Two-dimensional (2D) echocardiographic mitral valve orifice area (2D) and invasively calculated area (Gorlin) are the standard reference methods to measure stenotic mitral valve area. These two methods have been compared with the ‘ultimate’ gold standard, visual direct valve area assessment, and in particular 2D has been impressively shown to be a reliable measure of valve area more than 30 years ago as well as recently.1,2 The authors of the recent thought-provoking article in this field,3 have in the past carefully and convincingly shown4,5 that mitral valve orifice area determined by 3D echo planimetry (3D) agreed better with Gorlin than 2D, pressure half-time area (PHT), or area calculated from flow convergence zone analysis (PISA). They interpreted these findings as showing superiority of 3D over 2D against the standard of invasive haemodynamics, i.e. Gorlin.
In their current article,3 they suggest that 3D, instead of Gorlin, is the new reference method, because in a set of data from 26 patients 3D agreed better with the median values determined from the three conventional echo methods (2D, pressure half-time, and PISA) than Gorlin did. This finding is in line with their data in,5 where the agreements between Gorlin and each of the conventional echo methods were lower than the agreements of 3D and each of the conventional echo methods. However, to install 3D as the new reference method, it would have to be shown that the median value of 2D, PHT and PISA is a more reliable measure of valve area than the existing standards, Gorlin and 2D. Strictly speaking, this would require a comparison with direct (visual) valve area assessment, which was not available. Instead, the authors offer a comparison with a substitute, which was chosen to be the median of the three conventional echo methods 2D, PHT, and PISA. How good is this substitute for the ‘truth’, and how sure can we be that it is better than 2D alone, which the authors had discarded as an inferior to 3D previously?5 In this regard, it is instructive to consider the data provided in the work of Faletra et al.,2 who actually compared 2D, PHT, and PISA to ex-vivo assessment of the stenotic valves with a sizer. If one re-analyses their data, the agreement between direct sizing of the valve area and 2D (95% limits of agreement by Bland–Altman Analysis: –0.21; +0.29) was as good as the agreement between visual inspection and the median of 2D, PHT, and PISA values (95% limits of agreement: –0.25; +0.26). Thus, although taking the median of several independent measurements eliminates some random error, there is no necessity that this procedure produces a better agreement with the truth than a single good method, e.g. 2D. We therefore do not know whether the median values of 2D, PHT, and PISA values in the current study are any closer to the truth than 2D or Gorlin values. Hence, although it may well be that 3D echo actually is superior to traditional methods because of the inherently more powerful methodology and, most importantly, lower interobserver variability, this has not been proven yet.
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- Henry WL, Griffith JM, Michaelis LL, McIntosh CL, Morrow AG, Epstein SE. Measurement of mitral orifice area in patients with mitral valve disease by real-time, two-dimensional echocardiography. Circulation (1975) 51:827–1.
[Abstract/Free Full Text] - Faletra F, Pezzano A Jr, Fusco R, Mantero A, Corno R, Crivellaro W, et al. Measurement of mitral valve area in mitral stenosis: four echocardiographic methods compared with direct measurement of anatomic orifices. J Am Coll Cardiol (1996) 28:1190–7.[Abstract]
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[Abstract/Free Full Text] - Zamorano J, Perez de Isla L, Sugeng L, Cordeiro P, Rodrigo JL, Almeria C, et al. Non-invasive assessment of mitral valve area during percutaneous balloon mitral valvuloplasty: role of real-time 3D echocardiography. Eur Heart J (2004) 25:2086–91.
[Abstract/Free Full Text] - Zamorano J, Cordeiro P, Sugeng L, Perez de Isla L, Weinert L, Macaya C, et al. Real-time three-dimensional echocardiography for rheumatic mitral valve stenosis evaluation: an accurate and novel approach. J Am Coll Cardiol (2004) 43:2091–6.
[Abstract/Free Full Text]
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