Background: The geometric change of tricuspid valve (TV) and right ventricle (RV) after tricuspid annuloplasty (TAP) and determinant of residual significant tricuspid regurgitation (TR) have not been clearly demonstrated. Methods: In 31 patients who underwent TAP for significant functional TR, 2D and real-time 3D echo were performed at 1 day before surgery and ��� 7 days after surgery to evaluate the severity of TR and geometry of TV and RV. Results: After TAP, septal leaflet tenting angle was significantly increased (22짹7 to 30짹6째, p<0.001), and septal-lateral (3.1짹0.5 to 2.6짹0.6 cm, p<0.005) and antero-posterior (3.6짹0.6 to 3.2짹0.7 cm, p<0.01) annulus diameters were significantly decreased, whereas anterior (22짹9 to 25짹11째, p=0.21) and posterior (25짹8 to 25짹9째, p=0.82) leaflet tenting angles were not changed. The angle between TV annulus and lateral (112짹24 to 130짹13째, p<0.01) or posterior (108짹26 to 123짹19째, p<0.05) RV wall at end-systole significantly increased after TAP. TR distal jet area after TAP was significantly correlated with pre-TAP values of septal leaflet tenting angle (r=0.49, p<0.01) and TR distal jet area (r=0.45, p<0.05). By multiple linear regression analysis, pre-TAP septal leaflet tenting angle was the only significant predictor of post-TAP TR severity (p<0.05). Pre-TAP septal leaflet tenting angle ��� 26째predicted a residual significant TR (jet area ��� 5 cm2) after TAP with a sensitivity of 58% and a specificity of 84%. Conclusion: Septal leaflet tenting aggravates after TAP, and a large septal leaflet tenting before TAP predicts a residual significant TR after TAP. TV replacement may be considered rather than TAP in patients with a significant septal leaflet tenting.