Thirty-seven patients with symptomatic mitral stenosis underwent balloon dilatation of the mitral valve. Significant increases (p less than 0.001) were noted in both catheterization- and Doppler-determined valve area (0.9 +/- 0.3 to 1.8 +/- 0.8 and 0.9 +/- 0.2 to 1.7 +/- 0.5 cm2). However, catheterization and Doppler areas before and after valvuloplasty correlated less well (r = 0.51, p less than 0.002 and r = 0.47, p less than 0.005, respectively) than the catheterization-Doppler area correlation in a previous study of 59 consecutive patients with varying degrees of mitral stenosis (r = 0.84, p less than 0.001). Mitral valve area increases were independent of valve thickness estimated using 2-dimensional echocardiography. Flail mitral leaflet movement was not observed and the degree of mitral regurgitation qualitatively assessed using pulsed Doppler mapping techniques increased by greater than 1 of 4 grades in only 1 patient. The lateral mitral valve orifice diameter increased more than the anteroposterior diameter, suggesting commissural splitting as the mechanism of successful valvuloplasty. Increases (all p less than 0.0001) were noted in mitral valve EF slope (7 +/- 5 to 18 +/- 10 mm/s), excursion (11 +/- 5 to 13 +/- 4 mm), S20S interval (0.07 +/- 0.02 to 0.08 +/- 0.02 s) and cardiac output (4.2 +/- 1.3 to 5.3 +/- 2.0 liters/min). There were significant decreases (all p less than 0.001) in left atrial diameter (5.4 +/- 1.0 to 5.1 +/- 1.0 cm), mean catheterization gradient (15 +/- 5 to 8 +/- 4 mm Hg) and mean Doppler gradient (10 +/- 4 to 6 +/- 3 mm Hg).(ABSTRACT TRUNCATED AT 250 WORDS)