Association of right atrioventricular coupling indices and right atrial stiffness index with outcome in secondary tricuspid regurgitation

Background In patients with secondary tricuspid regurgitation (STR), the right atrial (RA) function is the most neglected yet highly valuable metric. Previous echocardiographic studies demonstrated the prognostic value of RA minimum volume and RA longitudinal reservoir strain (RALS) in STR patients, but the association with the outcome of the right atrioventricular coupling indices (RAVC) and RA stiffness index has never been explored before. Purpose Accordingly, we sought to evaluate the association with a composite endpoint of all-cause death and heart failure hospitalization of the: 1) speckle tracking echocardiography (STE)-derived RAVC computed as the ratio between RALS and right ventricular (RV) free wall strain (low values generally suggesting an abnormal atrioventricular coupling, with the RA not contributing effectively to RV filling, despite a good systolic performance of the RV); 2) volumetric RAVC calculated as the ratio between RA volume index (RAVi) and RV stroke volume index (RVSVi) (higher values indicating greater RA remodeling when compared to RVSVi and impaired atrioventricular coupling); and 3) RA stiffness index calculated as the ratio between RAVi and RALS. Methods 513 patients with STR (75 ± 13 years, 41% atrial STR, 58% severe STR) with complete echocardiographic datasets were included in this retrospective analysis of prospectively enrolled patients. Results After a mean follow-up of 18±15 months, 195 patients (38%) reached the composite endpoint. On spline curve modeling, the cut-off values associated with an excess event rate were: (1) <0.82 for STE-derived RAVC; (2) >1.23 for volumetric RAVC; and (3) >4.6 for RA stiffness index. On Kaplan-Meier analyses, when dividing the overall study population according to the cut-off values identified on spline curves modeling, significantly higher rates of events were recorded in patients with impaired RAVCs and RA stiffness index values (all p <0.05) (Figure 1). In hierarchical chi-square analyses, when added to different models including the most frequently evaulated echocardiographic parameters of RV systolic function and the pulmonary artery systolic pressure, STE-derived RAVC, volumetric RAVC, and RA stiffness index increased the models' predictive power (p values <0.05) (Figure 2). Conclusion In patients with STR, STE-derived RAVC, volumetric RAVC, and RA stiffness index are strongly associated with the risk of death and heart failure hospitalization. Assessing these echocardiographic parameters can improve risk stratification and facilitate the selection of the most suitable therapeutic approach.