Incremental predictive value of right atrioventricular coupling over right ventricular-pulmonary arterial coupling in secondary tricuspid regurgitation

Background Previous studies demonstrated a significant association with the outcomes of various echocardiographic surrogates of right ventricle-to-pulmonary artery (RV-PA) coupling in patients with secondary tricuspid regurgitation (STR). However, the predictive power of the right atrioventricular coupling (RAVC) indices and the right atrial (RA) stiffness index in STR patients has not been previously studied. Purpose Accordingly, we explored the incremental predictive benefit of the speckle tracking echocardiography (STE)-derived RAVC, volumetric RAVC, and RA stiffness indices over that of the RV forward stroke volume (fSV)/end-systolic volume (ESV), an echocardiographic metric of RV-PA coupling. The primary endpoint was a composite of all-cause death and heart failure hospitalization. STE-derived RAVC index was computed as the ratio between RA longitudinal reservoir strain (RALS) and RV free wall strain (lower values commonly indicating an impaired atrioventricular coupling, with the RA not supporting effectively the RV filling, despite a good systolic function of the RV); volumetric RAVC index was calculated as the ratio between RA volume index (RAVi) and RV SV index (RVSVi), (increased values reflecting greater RA remodeling relative to RVSVi and altered atrioventricular coupling); and RA stiffness index was quantified as the ratio between RAVi and RALS. Methods 513 patients with STR (mean age 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 Kaplan-Meier analyses, when dividing the overall study population into four subgroups, according to the cut-off values of the RAVC and RA stiffness indices identified on spline curves modeling as being associated with an increased risk and the threshold value of the fSV/ ESV previously reported as being associated with elevated risk, significantly higher rates of events were recorded in patients with impairments in both RAVC/ RA stiffness and RV-PA coupling (all p values <0.05) (Figure 1). However, in hierarchical chi-squared analyses, when added to a basal model including the fSV/ESV as an echocardiographic measure of RV-PA coupling, only volumetric RAVC significantly increased the model’s predictive power (p value < 0.05) (Figure 2). Finally, in multivariate Cox regression analyses, the association of volumetric RAVC (HR: 1.51 [95% CI, 1.15-1.97], p value 0.003) with the composite outcome was stronger than that of the fSV/ESV (HR: 0.92 [95% CI, 0.85-0.98], p value 0.015). Conclusion In patients with STR, the integration of both RAVC and RV-PA coupling indices results in refined outcomes stratification, with volumetric RAVC yielding the strongest benefit.