Clinical Impact of Size, Shape, and Orientation of the Tricuspid Annulus in Tricuspid Regurgitation as Assessed by Three-Dimensional Echocardiography

Background: Tricuspid annuloplasty for tricuspid regurgitation (TR) depends on the measurements of tricuspid annular diameter (TAD) obtained in an apical four-chamber view on two-dimensional (2D) transthoracic echocardiography (TTE). We performed a combined 2D and three-dimensional (3D) echocardiographic study to understand the impact of the size, shape, and orientation of a dilated annulus on the inconsistencies between measured 2D TTE-TAD and the actual annular diameter. Methods: A total of 185 patients with grade ≥3+ TR and 50 controls underwent 2D TTE and 3D transesophageal echocardiography (TEE) assessment of the tricuspid valve. The 3D TEE-TAD, defined as the longest dimension, and tricuspid annulus (TA) eccentricity index, defined as the shortest/longest dimension ratio, were obtained. The angle between the major tricuspid annulus axis and interatrial septum parallel to the vertical axis (α°) was measured as an index of TA orientation. Results: Compared with controls, TR subgroups had a larger α° irrespective of TR etiology and cardiac rhythm (P < .05), with the posteriorly displaced TA most frequently noted in patients with atrial fibrillation. An excellent correlation was found between 3D TEE-TAD and 2D TTE-TAD, but 2D TTE-TAD was significantly smaller than 3D TEE-TAD (35.9 ± 5.4 vs 39.8 ± 5.7 mm; P < .001; bias, 3.9 ± 2.6 mm; limits of agreement, −1.1-8.9 mm). After multivariate adjustment, a larger 3D TEE-TAD and larger absolute value of 90° − α° were independent determinants of the bias between 3D TEE-TAD and 2D TTE-TAD (both P < .001). Conclusions: The inconsistencies between measured 2D TTE-TAD and the actual annular diameter can be explained through morphologic factors such as TA size and orientation.