Right atrial phenotype determines structural reversibility after transcatheter tricuspid repair

Background Right atrial (RA) remodeling is increasingly recognized as a determinant of status and outcomes in severe tricuspid regurgitation (TR), yet longitudinal RA structural, functional, and geometric trajectories after transcatheter tricuspid edge-to-edge repair (T-TEER) remain poorly defined. Objectives To characterize longitudinal RA remodeling after T-TEER and to identify determinants of late RA structural re-dilatation and acute and late changes in RA function. Methods We performed a single-center retrospective analysis of a prospectively enrolled cohort of 131 patients undergoing T-TEER between March 2021–December 2025. Serial transthoracic echocardiography was analyzed by a blinded core laboratory at baseline, pre-discharge, 6 months, and 12 months. RA volume index (RAVI) was measured by the area–length method; RA reservoir function was quantified as peak right atrial strain (PARS) by 2D speckle tracking; RA geometry was assessed by the RA sphericity ratio (RASR). Longitudinal changes were evaluated using linear mixed-effects models. Late structural remodeling was defined as %ΔRAVI from pre-discharge to 12 months. Associations between RASR and %ΔRAVI were tested using correlation and multivariable regression adjusted for baseline RAVI, rhythm, and residual TR. Results RAVI demonstrated a biphasic trajectory (χ²(3)=45.06, p<0.001): 69.9 mL/m² (95% CI 64.8–75.1) at baseline, 58.7 (53.5–63.8) pre-discharge, 63.0 (57.7–68.3) at 6 months, and 68.8 (63.3–74.3) at 12 months. In contrast, PARS declined acutely from 11.3% (95% CI 10.3–12.4) to 9.6% (8.5–10.6) at pre-discharge (p=0.002) and showed no recovery through 12 months. In patients with durable procedural success, baseline right atrial geometry independently predicted late structural remodeling: for each +0.10 increase in baseline right atrial sphericity ratio (RASR), late right atrial re-dilatation (%ΔRAVI from pre-discharge to 12 months) decreased by 9.11% (95% CI −16.9 to −1.4; p = 0.022). Acute PARS reduction was independently associated with change in RV free-wall longitudinal strain (β=−0.17 per 1%, p=0.045) and baseline PARS (p<0.001), whereas no variable predicted late PARS change (all p>0.2). Conclusions After T-TEER, RA remodeling is characterized by a marked structure–function dissociation: biphasic volumetric unloading with late re-dilatation, alongside persistent functional impairment. Baseline RA geometry (RASR) identifies patients at risk for late structural failure, while RA functional recovery appears limited, supporting a dominant role of atrial myocardial substrate in shaping remodeling after valve intervention.