The aim of this study was to assess the initial and midterm outcome of patients with severe pulmonary hypertension undergoing percutaneous mitral valvuloplasty (PMV). Accordingly, the baseline characteristics, immediate results and follow-up of 64 consecutive patients with severe pulmonary artery hypertension (systolic pulmonary artery pressure > or = 60 mm Hg on cardiac catheterization) (group I) were analyzed and compared with those of 194 consecutive patients with lower pulmonary pressures (group II). Patients in group I were more symptomatic (New York Heart Association functional class > or = III, 72 vs 40%, p < 0.001) and had higher echocardiographic scores (8.6 +/- 2 vs 7.4 +/- 1, p < 0.05). Before PMV, mitral gradient was higher (17 +/- 6 vs 13 +/- 5 mm Hg, p < 0.025) and mitral valve area smaller (0.79 +/- 0.2 vs 0.96 +/- 0.2 cm2, p < 0.005) in group I patients, who also had higher pulmonary vascular resistances (469 +/- 299 vs 157 +/- 125 dynes s-1 cm-5, p < 0.005). On multivariate analysis patients in group I were more symptomatic, had smaller mitral valve areas and higher mitral gradients. PMV success (area gain > 50% without complications) was similar (89 vs 87%) in both groups. After PMV final mitral gradient (5 +/- 2 vs 4 +/- 2 mm Hg) and area (1.82 +/- 0.5 vs 1.87 +/- 0.5 cm2) were similar in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)