THE SIMPLIFIED CONTINUITY EQUATION - ABSE NCE OF PREDICTIVE VALUE IN THE ASSESSMENT OF THE SEVERITY OF MITRAL-STENOSIS

The object of this study was to assess the accuracy of the simplified continuity equation (SCE) defined as the ratio of velocity time integr als (VTI) of the aortic or pulmonary to mitral orifice in the evaluati on of severe mitral stenosis. The results of the continuity equation a nd VTI ratios were compared with the Gorlin catheter valve area in 70 patients with pure mitral stenosis in sinus rhythm. The continuity equ ation (CE) and SCE were significantly correlated (p < 0.01) with the G orlin surface area with a better coefficient with the CE (r = 0.86) th an with the VTI ratio (r = 0.74). The patient population was divided i nto 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 v alue of the CE of 1.11 +/- 0.22 CM2 and of the SCE of 0. 32 +/- 0.09. In Group II (mitral valve area greater-than-or-equal-to 1.5 CM2), 32 p atients 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 o verlap between the two groups (19 patients of Group I and 9 patients o f Group II). Analysis of the predictive value of the CE and SCE in the diagnosis of severe mitral stenosis as defined as a valve surface are a less than 1.5 CM2 shows excellent sensitivity (97 %) and speciticity (91 %) of the CE but though the SCE has an excellent specificity (100 %) for values less than 0.3, the senitivity is poor (40 %). Therefore , though the SCE is significantly correlated to the Gorlin surface are a, it is not a reliable predictive method for detecting severe mitral stenosis.