SUMMARY We examined the long-term effects of closed instrumental mitral commissurotomy on mitral valve area (MVA) in 18 patients, followed for as long as 14 years after successful operation. Each patient had preoperative and early postoperative cardiac catheterization; a late postoperative determination of MVA was obtained 10-14 years (mean 12.2 years) after commissurotomy. In 17 patients, the MVA was determined by cross-sectional echocardiography and in one patient by repeat cardiac catheterization. Thirteen of 18 patients had no change in MVA between early postoperative study (mean MVA = 2.7 cm2) and late postoperative study (mean MVA = 2.9 cm2). MVA in five patients decreased 0.7-2.2 cm2 (mean 1.4 cm2) during the followup period. In these five patients, the mean MVA at early postoperative study was 2.7 cm2 and at late postoperative study was 1.3 cm2 (p < 0.001). At late postoperative evaluation, cardiac symptoms were associated with severity of mitral stenosis but did not predict restenosis. A successful, closed, instrumental mitral commissurotomy can provide substantial long-term improvement in MVA.RHEUMATIC MITRAL STENOSIS is an acquired form of valvular heart disease characterized by diffuse thickening of the mitral leaflets, fusion of the commissures, and shortening and fusion of the chordae tendineae. These pathologic lesions combine to decrease the size of the 'mitral valve orifice, thereby restricting the flow of blood into the left ventricle. When the decrease in mitral valve area (MVA) becomes critical, surgical correction of the valvular lesion is frequently required. Surgical improvement in MVA may be accomplished by prosthetic mitral valve replacement, or, in selected cases, by mitral commissurotomy. Mitral commissurotomy appears to be preferable, since the operative morbidity and mortality are less and postoperative complications fewer than those associated with valve replacement.There is concern, however, that restenosis of the valve may occur after a successful commissurotomy, necessitating a second commissurotomy or a valve replacement. On the basis of clinical and hemodynamic studies, many investigators report that reoperation is often required after a commissurot- the long-term changes in MVA after commissurotomy, they have been limited to either rightheart catheterization data or the study of primarily those patients with recurrent symptoms.6"-As a result, data concerning the overall, long-term effects of successful mitral commissurotomy on the MVA in patients with and without recurrent symptoms are unavailable. This is important information, since the decision to perform a commissurotomy depends, in part, on the expected long-term results. We report our findings in a group of patients who had a documented successful commissurotomy, and who were then followed for as long as 14 years to determine the long-term effects of the operation on MVA and the incidence of restenosis. Methods To determine the long-term effects of mitral valve commissurotomy on MVA, we studied only patients who had pure...