Abstract Background The assessment of tricuspid valve (TV) and functional tricuspid regurgitation (FTR) in left side valvular disease is crucial in assessing the need for surgical intervention. Despite the declining incidence of rheumatic disease, it remains a a common cause of valvulopathy. According to current guidelines, TV surgery is recommended in presence of severe TR or non-severe with annulus dilatation assessed by two-dimensional echo (2DE). Objectives To assess tricuspid annulus (TA) 3D dimensions in relation to the severity of tricuspid regurgitation (TR) and to identify new parameters associated with the presence of severe TR in this scenario. Methods Fifty patients (Age: 69±9, 82% women) with rheumatic heart disease without previous valve replacement and functional tricuspid regurgitation (FTR) were prospectively included. Two-dimensional echocardiography (2DE) and three-dimensional transthoracic full-volume datasets of the tricuspid valve (TV) were acquired. Two orthogonal planes corresponding to the anatomical antero-posterior (APD), septum-lateral (SLD), long intercommisural (LID), and area (A3D) of the TA were analyzed by 3D transesophageal echocardiography (3DTE) (Figure 1), in addition to 2D diameter. TR was graded into two groups: severe (n=14) or non-severe (n=26). The area under the curve (AUC), sensitivity (Se), and specificity (Sp) to identify the presence of severe FTR were calculated. Results All parameters differed significantly (p<0.05) between the two groups (2D: 18.6±1.9 vs. 23.3±2.0 mm/m2; APD 17.0±3.3 vs. 21.5±3.0 mm/m2; SLD: 18.9±2.0 vs. 22.5±2.0 mm/m2; LID: 20.9±2.6 vs. 26.1±3.5 mm/m2; A: 5.6±1.3 vs. 7.6±1.4 cm2/m2). 2D diameter (Cut-off point: 20.6 mm/m2, AUC: 0.850, Se: 86%, Sp: 72%), A3D (Cut-off point: 6.5 cm2/m2, AUC: 0.835, Se: 86%, Sp: 78%), and LID (Cut-off point: 23.3 mm/m2, AUC: 0.833, Se: 78.6%, Sp: 77.8%) were the parameters with the best performance for severe FTR detection. Conclusions New 3D-derived parameters provide relevant information in the assessment of TA and offer good diagnostic performance for identifying severe FTR in this subgroup of patients.2D/3D Echo TA measurements