Frequency and severity of mitral regurgitation one year after balloon mitral valvuloplasty. Mitral regurgitation (MR) was evaluated by Doppler echocardiography in 59 patients with mitral stenosis before, immediately after and 1 year after balloon mitral valvuloplasty (BMV). The severity of MR was graded on a scale from 1+ to 4+. Echocardiographic and hemodynamic variables were analyzed to study the potential factor(s) that might predict the long-term persistence of MR. Echocardiographic variables were mitral valve thickness and motion, subvalvular change, left atrial dimension, commissural calcification and effective balloon/mitral anular diameters. Hemodynamic variables were mitral pressure gradient, pulmonary arterial pressure, ejection fraction, mitral valve area index, age, gender and cardiac rhythm. Mitral valve area index increased from 0.9 +/- 0.5 to 1.5 +/- 0.8 cm2/m2 immediately after BMW, and to 1.4 +/- 0.3 cm2/m2 at 1 year follow-up (p less than 0.01). Immediately after BMV, MR grading did not change in 30 patients (51%), increased by 1+ in 23 patients (39%), by 2+ in 2 patients (3.3%) and by 3+ in 2 patients (3.3%), and decreased by 1+ in 2 others. At 1-year follow-up, only 1 patient with severe MR required valve replacement. Fifty-one patients (88%) had no change in the extent of MR (less than or equal to 1+) and 6 patients (10%) had a 1-grade decrease in their MR; only 1 patient had a 1-grade increase in MR. No clinical or hemodynamic variables or morphologic characteristics of the mitral valve could predict the development of significant MR after BMV. It is concluded that an increment in MR severity less than or equal to 2+ is frequently seen after BMV. 