Although Inoue balloon mitral commissurotomy (BMC) offers excellent short-term results, there remains a paucity of data on its long-term (> or =3 yr) outcome. We therefore analyzed the outcome of 68 consecutive patients who had regular long-term clinical and serial echocardiographic follow-up of > or =3 yr after successful BMC. The procedure provided significant improvements in transmitral valve gradient (13+/-6 mmHg before to 5+/-2 mmHg after BMC, P = 0.0001), left atrial pressure (21+/-6 mmHg before to 14+/-5 mmHg after BMC, P = 0.0001), and mitral valve area (0.8+/-0.2 cm2 before to 1.7+/-0.4 cm2 after BMC, P = 0.0001) without incurring > grade 2+ angiographic mitral regurgitation. At a mean follow-up of 44+/-9 mos (range, 36-63 mo), functional benefits were maintained in 91% of patients. Serial echocardiographic evaluations performed in 97% of patients revealed a restenosis rate of 15% (defined as a loss of >50% initial gain in valve area or a valve area of <1.5 cm2). No strokes or deaths were encountered. Of the 15 clinical, echocardiographic, and procedural variables analyzed in a multivariate model, only the presence of chronic atrial fibrillation was an independent correlate of restenosis (P < 0.05). It was clearly more common in patients with than those without restenosis (100% with vs. 57%, respectively, P = 0.009). In conclusion, our study shows that BMC confers maintained long-term functional benefits and a low anatomic restenosis rate 23 yr after BMC.