[Simplified continuity equation: absence of predictive value in assessing severity of mitral valve stenosis]

The object of this study was to assess the accuracy of the simplified continuity equation (SCE) defined as the ratio of velocity time integrals (VTI) of the aortic or pulmonary to mitral orifice in the evaluation of severe mitral stenosis. The results of the continuity equation and VTI ratios were compared with the Gorlin catheter valve area in 70 patients with pure mitral stenosis in sinus rhythm. The continuity equation (CE) and SCE were significantly correlated (p < 0.01) with the Gorlin surface area with a better coefficient with the CE (r = 0.86) than with the VTI ratio (r = 0.74). The patient population was divided into two groups depending on the severity of mitral stenosis; Group I had catheter valve areas of less than 1.5 cm2: 38 patients had mean value of the CE of 1.11 +/- 0.22 cm2 and of the SCE of 0.32 +/- 0.09. In Group II (mitral valve area > or = 1.5 cm2), 32 patients had a mean CE value of 1.92 +/- 0.29 cm2 and a SCE value of 0.56 +/- 0.14. Only two patients in Group I had SCE values greater than 0.5. Conversely, no patients in Group II had a SCE value of less than 0.3. For a range of SCE values of 0.3 to 0.5, there was an important overlap between the two groups (19 patients of Group I and 9 patients of Group II).(ABSTRACT TRUNCATED AT 250 WORDS)