AimTo evaluate the reliability of the mitral leaflet separation (MLS) index against the traditional echocardiographic methods in measuring mitral valve area (MVA) pre and post percutaneous balloon mitral valvuloplasty (PBMV).MethodsNinety patients suffering symptomatic moderate to severe MS underwent PBMV at Ain Shams University Hospital in cardiology department. Seventy of the patients were females representing 77.8% and 20 were males representing 22.2%. Their age ranged from 22 to 56 years. All patients were subjected to full transthoracic echocardiography (TTE) examination pre and post PBMV. MLS index was introduced as a comparative parameter with traditional echocardiographic methods for assessment of MVA, measuring average of distance between tips of MV leaflets in parasternal long axis and four chamber two dimensional echocardiographic views.ResultsMVA increased from 0.95 ± 0.28 to 2.21 ± 0.41 cm2 (P=0.001) using 2D planimetry; and increased from 0.93 ± 0.23 to 2.21 ± 0.46 cm2 (P= 0.0011) by pressure half time method (PHT). MLS index was correlated with MVA by 2D planimetry pre and post PBMV (r=0.453) and (r=0.668) respectively (p=0.0001) and strongly correlated with MVA using PHT post PBMV (r=0.768) (p=0.0001). Post PBMV 14 patients suffered significant mitral regurgitation 3 of them were transferred to surgery. MLS index above 11.75 mm and below 9.15 mm had excellent positive predictive value for detecting mild and severe MS respectively.ConclusionThe MLS index it is a simple and effective method for assessment of the MVA, it has an excellent correlation with MVA with an excellent sensitivity and specificity for the prediction of effective MVA. The MLS index cannot evaluate outcome of PBMV because it is an anatomical parameter and not flow dependent thus does not correlate with grades of mitral regurgitation.