In order to identify the determinants for surgical procedures in mitral stenosis, we evaluated two-dimensional echocardiographic findings of the mitral valve and subvalvular structures in 35 patients undergoing open mitral commissurotomy (OMC) or valve replacement (MVR). As indices of a degree of subvalvular shortening and valvular flexibility, the distance between the mitral ring and the tip of the anterior mitral leaflet was measured by the LV long-axis view by in both midsystole (S) and early diastole (D). As a possible major determinant for MVR, a degree of valvular calcification (C) was semi-quantatively scored according to the extent of abnormally strong echo density. In nine of 11 patients undergoing MVR, a main reason for selecting MVR was a marked thickening or shortening of subvalvular structures. In patients in whom OMC was feasible, the degree of improvement of the mitral valve area (delta MVA) was assessed by the pre- and post-operative mitral valve areas (MVA) measured on the LV short-axis view, which were averaged 0.15 and 1.38 cm2, respectively. RESULTS The index C was significantly higher in cases with MVR than those with OMC (9.2 +/- 2.6 vs 4.7 +/- 2.3 points, p less than 0.001), although there was a significant overlap between these two groups and index C did not correlate with delta MVA in the OMC patients. Similarly, the value S was significantly smaller in patients undergoing MVR than those undergoing OMC (1.2 +/- 0.4 vs 0.7 +/- 0.2 cm, p less than 0.001), though S did not correlate with delta MVA. On the other hand, the index of valve flexibility D--S was smaller in patients undergoing MVR (0.5 +/- 0.3 vs 0.8 +/- 0.3 cm, p less than 0.05) and correlated well with delta MVA (delta MVA = 0.699 x (D--S)+0.007, R = 0.678, p less than 0.02) in patients undergoing OMC. Furthermore, in all patients undergoing OMC with D--S greater than or equal to 0.8 cm, delta MVA was above 0.5 cm2, contrasting with delta MVA of 0.5 cm2 or less in 6 of 7 patients with D--S less than 0.7 cm. Using these indices, surgical procedures were successfully predicted in another 7 prospectively studied patients and predicted delta MVA in 4 patients was quite comparable with actual delta MVA. It was concluded that measurements of S and D by two-dimensional echocardiography are useful, 1) to predict patients requiring MVR and 2) to predict patients with inadequate delta MVA in whom OMC is surgically feasible.