During 241 consecutive percutaneous mitral valvotomy (PMV) procedures performed with the Inoue balloon, 16 patients (6.6%) developed severe mitral regurgitation (MR). Baseline clinical, echocardiographic (Doppler mitral valve area and Wilkins' score) and hemodynamic data were not different from those of patients without this complication. Severe MR occurred during the first inflation in 7 patients and after several stepwise inflations in 9. Although maximal balloon size was similar in both groups, unusual indentations and subvalvular inflations were more frequently observed in patients who developed severe MR. Early mitral valve replacement was required in 6 patients. AN of them had a leaflet rupture either along the midportion (2 patients), along a commissure (4 patients), or both. Commissural calcium was present in 5 valves and 5 also had severe subvalvular involvement that had been underestimated by echocardiography. Of the 10 nonsurgically treated patients, 4 had chordal rupture by echocardiographic criteria, whereas in the remaining 6 the precise mechanism of MR could not be determined. During follow-up (11.4 +/- 4 months, range 1 to 30), 1 patient required surgery for symptoms and the remaining 9 were symptomatically improved and free of left ventricular dilatation. In conclusion, severe MR complicated 6.6% of PMV procedures with the Inoue balloon, and its mechanism was leaflet or chordal rupture. Although one third of the patients required early mitral surgery, most of the remaining obtained midterm symptomatic benefit.
