Objective To determine whether successful valvuloplasty causes an increase of mitral valve area reserve in patients with mitral stenosis, isoproterenol stress echocardiography was used to compare mitral valve area and hemodynamic changes between pre- and post- valvuloplasty under conditions of increased cardiac work. Methods Thirtyeight patients with pure rheumatic mitral stenosis who had received successful percutaneous balloon valvulo plasty underwent isoproterenol stress echocardiography pre- and post- valvuloplasty. Mitral valve area (by direct planimetry of two- dimensional echocardiography), mean transmitral pressure gradient (by continuous-wave Doppler echocardiography), and cardiac output (by M -mode echocardiography) were measured at rest and under isoproterenol stress to achieve heart rate of different stages. Results Mitral valve area (0. 91± 0. 28 to 1. 87±0.23cm2, P ＜0.01), mean transmitral pressure gradient ( 12.5 ± 6. 3 to 3.9 ± 1.9mmHg, P ＜ 0.01 ) and cardiac output (3.93 ± 1.44to 4. 73 ± 1.01 L/min, P ＜ 0.05) at rest between pre - and post -valvuloplasty were significantly different.Pre-valvuloplasty, as heart rate increased under stress, mean transmitral pressure gradient increased significantly ( P ＜ 0.01 ), but there were no significant differences in the measurements of mitral valve area and cardiac output (both P ＞ 0.05). In contrast, as heart rate increased post- valvuloplasty, there was a significant increase in mean transmitral pressure gradient (P ＜ 0.01), but both mitral valve area and cardiac output further increased significantly (both P ＜ 0. 01) . Moreover, valvuloplasty decreased mean transmitral pressure gradient at peak heart rate from 23.0 ± 4. 5 to 7.75 ± 2.30 mmHg ( P ＜ 0.01 ) under submaximal stress. Conclusions Successful percu taneous balloon valvuloplasty soon causes a significant increase of mitral valve area reserve in patients with mitral stenosis, which is markedly manifested under conditions of hemodynamic stress. Stress echocardiography provides a safe, feasible and non-invasive means of assessing this reserve capacity.