Balloon mitral valvuloplasty has been reported to give equal or less positive results after previous commissurotomy than after a first procedure. Percutaneous mechanical mitral commissurotomy (PMMC) is a new technique that has not yet been evaluated in this subset of patients. Of 1,175 PMMC procedures (1,175 patients), 173 patients (14.7%) had previous commissurotomy; patients were older (40 vs 35 years of age, p <0.0001) and more often in atrial fibrillation (34% vs 21%, p = 0.0016) than were patients who had not undergone previous commissurotomy. The baseline transmitral gradient was lower (17 +/- 8 vs 19 +/- 8 mm Hg, p <0.002) and the echocardiographic Wilkins score was higher (8.7 +/- 1.9 vs 7.6 +/- 1.8, p <0.0001) for patients who underwent previous commissurotomy. Baseline mitral valve area was comparable between the 2 groups (0.96 +/- 0.21 vs 0.93 +/- 0.24 cm(2)). Immediate results were satisfactory, although slightly less favorable after previous commissurotomy, with a final mitral valve area of 2.01 +/- 0.30 versus 2.12 +/- 0.36 cm(2) (p <0.0001), and a residual transvalvular gradient of 5.0 +/- 3.6 versus 4.2 +/- 4.1 mm Hg (p = 0.003). The rates of procedural success (93%) and severe complications (4.7%) were comparable between the 2 groups. Thus, PMMC is an effective and safe technique for the treatment of mitral restenosis after previous commissurotomy.