Objective: We aimed to investigate the utility of right ventricular (RV) dyssynchrony to assess functional capacity utilizing 6-minute walking test distance (6MWTD) and to measure brain natriuretic peptide levels (BNP) in patients with mitral stenosis (MS) and to study its value to predict adverse outcome following percutaneous balloon mitral valvuloplasty (PBMV). Methods: A total of 108 patients with moderate to severe MS (26.5 ± 7.5 years) were included in this study. All were candidates for PBMV. RV strain curves were obtained using two-dimensional speckle-tracking echocardiography, and standard deviation (SD) of 4 segments without RV apex (-SD4) was also assessed. 6MWT and BNP were before and after 12 months following PBMV. Results: RV-SD4 was significantly prolonged in patients with MS compared with controls (P < 0.001). Patients with 6MWTD ≤300 m had a significantly increased RV-SD4 (P < 0.001) and had higher BNP values (P < 0.03) compared with those with 6MWTD >300 m. RV-SD4 showed a strong correlation with 6MWT and BNP level. RV-SD4 was the strongest independent predictor of adverse outcome following PBMV (P < 0.0001). Receiver operating characteristic analysis showed that RV-SD4 ≥24 ms was the cutoff value which predicts the adverse outcome following PBMV. A considerable improvement of mean 6MWT with significant reduction of BNP levels after 12 months of follow-up (P < 0.001) in subjects with RV dyssynchrony <24 ms. Conclusion: Right ventricular dyssynchrony is a useful predictor of functional status, as assessed with 6MWTD and BNP level in patients with MS. Furthermore, it might be considered as an independent predictor of adverse outcome following PMBV. K E Y W O R D S 6-minute walking test, balloon valvuloplasty, dyssynchrony, mitral stenosis