Mitral leaflet separation index: A new method for the evaluation of the severity of mitral stenosis? Usefulness before and after percutaneous mitral commissurotomy

Background: Two-dimensional planimetry (MVA(2D)) is the reference method for the evaluation of the severity of mitral stenosis (MS) but requires experienced operators. The mitral leaflet separation (MLS) index (distance between mitral leaflets) was recently presented as a reliable measure of MS severity. This method has the advantage of simplicity but has not been evaluated in a nonselected series of consecutive patients before and after percutaneous mitral commissurotomy (PMC). Methods: Patients referred for MS evaluation in our institution between February and September 2006 were prospectively enrolled in the present study. The only exclusion criterion was nonfeasible planimetry. MLS index was obtained by averaging the maximal leaflet separation distance at the tips in diastole in parasternal long-axis and apical four-chamber views. Planimetry was used as reference. Results: Ninety consecutive patients were enrolled, and 116 examinations were performed: 55 before PMC and 61 after PMC. Overall mean MVA(2D) was 1.48 +/- 0.52 cm(2), MLS index was 1.01 +/- 0.24 cm, and a good correlation between both measurements was observed (r = 0.77, P < .00001). MLS index was significantly different between patients with severe (MVA(2D) >= 1,5 cm(2)) and nonsevere MS (0.87 +/- 0.17 vs. 1.17 +/- 0.21 cm, P < .0001), but there was an important overlap. No threshold value could predict a nonsevere MS with both a sensitivity and a specificity greater than 80%. A threshold value of 0.97 cm provided the best combination of sensitivity and specificity (86% and 75%, respectively). However, an MLS index of 1.2 cm or more provided a good specificity and positive predictive values for the diagnosis of nonsevere MS (85% and 89%, respectively) and an MLS index of less than 0.8 cm an excellent specificity and positive predictive value for severe MS (98% and 96%, respectively). Conclusion: The MLS index cannot be considered as a substitute for MVA, but it can be used as a semi-quantitative and complementary method for the integrative assessment of MS severity.