Percutaneous mitral valvuloplasty (PMV) was performed by the anterograde transseptal approach (double balloon technique) in 154 patients with symptomatic mitral stenosis. The mean age of the patients was high (53 +/- 14 years), 87% were women, 68% were in functional Classes III or IV of the NYHA and 37 (24%) had previously undergone surgical commissurotomy. The echocardiographic score was 8.5 +/- 1.6. PMV could not be completed because of a technical failure or a complication in 14 cases (9%). In the other patients, PMV increased mitral surface area from 1.0 +/- 0.3 to 2.0 +/- 0.8 cm2 (p less than 0.0001). A haemodynamic success (greater than or equal to 25% increase in mitral surface area and final area greater than or equal to 1.5 cm2) was obtained in 104 patients (75%). The predicting factors of success were echocardiographic score (8.1 +/- 1.4 versus 9.4 +/- 1.7; p less than 0.0001) and cardiac output (4.0 +/- 1.1 versus 3.0 +/- 1.0/l/min; p less than 0.0001). The duration of the procedure, the technical failure rate and the frequency of cardiac perforation were influenced by the learning curve. The degree of mitral regurgitation increased after PMV in 34% of cases, usually by one grade and without clinical or haemodynamic consequences. Acute mitral regurgitation was a rare (3%) and impredictable complication. An interatrial shunt was demonstrated in 80% of cases after PMV but the Qp/Qs ratio rarely exceeded 1.5 (11%). This shunt disappeared or decreased in the majority of cases during follow-up. The clinical result was an improvement of at least one functional Class in 83% of cases at 6 months.(ABSTRACT TRUNCATED AT 250 WORDS)