Background : Isolated tricuspid regurgitation(TR) is a clinical dilemma for management. Although functional TR is thought to be caused by TV annulus dilatation and tethering of the tricuspid leaflet, the mechanism of isolated TR has not been explored previously. We hypothesized that RV remodeling and dysfunction would be the most important mechanism for isolated TR. Therefore, we designed to evaluate RV function and TV deformations in patients with isolated TR. Methods and Results : 14 patients with isolated TR had complete echocardiographic exam. RV volume and ejection fraction(EF) were determined with the apical views. The distance of TV tethering was measured from the annulus plane to the coaptation point and tethering area by tracing the leaflets from the annulus plane. These parameters were compared with 14 age and gender matched controls and 14 patients with functional TR. The most common cause of TR was incomplete coaptation due to idiopathic annular dilatation. Other causes were chordae rupture and prolapse of TV leaflet. Comparing with controls, RV end-diastolic and end-systolic volumes, annular diameters were significantly larger in patients with isolated TR. RV EF and tricuspid annular fractional shortening were lower in patients with isolated TR. Tenting area and tenting distance measured at midsystole were significantly higher in patients with isolated TR. However, there were no significant differences between isolated TR and functional TR. (Table) Conclusion : Isolated TR was associated with RV remodeling and dysfunction with annular dilatation, decreased annular fractional shortening, tethering of tricuspid leaflets.