[Contribution of the continuity equation for the assessment of mitral valve area in mitral stenosis].

The aim of this study was to evaluate the continuity equation in the quantification of mitral valve area in mitral stenosis, the area being considered as the product of the area of the left ventricular outflow tract multiplied by the ratio of the velocity time integrals of the aortic or pulmonary flow to that mitral flow. The continuity equation was compared to two other echocardiographic methods, planimetry and Hatle's method, and to the results obtained at catheterization using the Gorlin formula in a population of 44 patients with mitral stenosis. All were in sinus rhythm; twelve had Grade I mitral regurgitation and 9 patients had Grade I aortic regurgitation. Excellent correlation were observed between the values obtained by the continuity equation and planimetry (r = 0.91; SEE = 0.19 cm2; p less than 0.001) and Hatle's method (r = 0.87; SEE = 0.20 cm2, p less than 0.001). The correlation with the catheter values were also excellent (r = 0.83; SD = 0.22 cm2, p less than 0.001), better than those observed with Hatle's method (r = 0.73; SEE = 0.27 cm2, p less than 0.001) and very similar to those obtained with planimetry (r = 0.87; SEE = 0.23 cm2, p less than 0.001). The sensibility and specificity of the continuity equation for the diagnosis of severe mitral stenosis (surface less than 1.5 cm2) were 90% and 100% respectively, when those of Hatle's method were 88% and 91% respectively. The continuity equation in the evaluation of mitral valve area in mitral stenosis seems to be reliable and accurate compared with catheter data, and superior to Hatle's method.