Introduction: Tricuspid annulus (TA) measurement is essential to refer patients for percutaneous and surgical procedures. Current guidelines recommend to assess TA sizing using linear dimension obtained by 2D echocardiography (2DE). However TA is a complex 3D structure. Aim. To identify the physiological determinants of TA geometry parameters and their reference values using 3D echocardiography (3DE) and a novel dedicated software package in healthy volunteers.
Methods: 254 healthy volunteers (113 men, mean age 47±11 years) were enrolled and evaluated using both 2D and 3DE. TA analysis by 3DE was feasible in 228 of them (feasibility= 90%). TA 3DE area, perimeter, diameters, sphericity index and coaptation were assessed at end-diastole using a dedicated software package (4D AutoTVQ, GE Healthcare, Horten, N). Right atrial (RA) and ventricular (RV) volumes were measured using 3DE.
Results: Normal values of 3D TA geometry parameters, RV and RA volumes are: 3D area 5.5 ± 1.1 cm2/m2, perimeter 6.4 ± 0.9 cm/m2, 4ch diameter 19 ± 3 mm/ m2, major diameter 21 ± 2 mm/m2, minor diameter 17 2 mm/m2, sphericity index 82 ± 10%, RV end-diastolic volume 57 ± 16ml/m2, RV end-systolic volume 23 ± 8ml/m2, RV EF 59 ± 5%, RA volume 29 ± 7ml/m2, p< 0.001. 3D TA area, perimeter and diameters correlated with BSA (r= 0.30 to r= 0.59, p< 0.0001) and were significantly larger in men than in women, independently of BSA (p< 0.0001). Conversely, there were no age-related changes in TA parameters (r< 0.20, p= 0.0001). 2D TA diameters measured in apical 4-chamber (4ch) and RV focused views were significantly smaller than the corresponding 3DE apical 4ch diameter (16 ± 3 and 17 ± 3 vs. 19 ± 3, respectively, p< 0.0001). RA maximal volumes had the strongest correlation with 3D TA area (r= 0.71), compared with RV end-diastolic (r= 0.62) and end-systolic (r= 0.57) volumes (p< 0.0001). At multivariable linear regression analysis, RA maximal volume and RV end-diastolic volumes were independent predictors of 3D TA area (R2= 0.54, p< 0.0001).
Conclusions: Reference values for TA metrics should be sex-specific and indexed to BSA. 2DE underestimates actual TA dimensions. RA and RV volumes correlate significantly with TA area and are independent predictors of its size at end-diastole in our study.