Association of the right atrial stiffness index with symptom severity categorized by the New York Heart Association functional class in patients with secondary tricuspid regurgitation

Background The utility of the left atrial stiffness index in predicting limited exertional tolerance and impaired hemodynamics in patients with mitral regurgitation and left-sided heart failure has received substantial research attention. However, the clinical significance of its right-sided counterpart has not been addressed before. Purpose Accordingly, we explored the association of the right atrial (RA) stiffness index with symptomatic status assessed via the New York Heart Association (NYHA) functional class in a large cohort of patients with secondary tricuspid regurgitation (STR). The RA stiffness index was computed as the ratio between RA volume index (RAVi) and RA longitudinal reservoir strain (RALS). Methods The study was a retrospective analysis of prospectively enrolled patients. A total of 513 patients with STR (mean age 75 ± 13 years, 41% atrial STR, 58% severe STR) and complete echocardiographic datasets were included. Results When dichotomizing patients as NYHA class ≥ III vs. NYHA class I–II, those with NYHA class III–IV had significantly higher RA stiffness index (p = 0.0011, Wilcoxon test). In multivariable logistic regression (adjusted for age, sex, and right ventricular fractional area change), RA stiffness index was an independent predictor of NYHA class: OR 1.01, p=0.04. A model including RA stiffness index, RA area, chronic kidney disease, and STR regurgitant volume confirmed RA stiffness index as an independent predictor of higher NYHA class (OR 1.02, p=0.039). After a mean follow-up of 18±15 months, 195 patients (38%) reached a composite endpoint of heart failure hospitalization and all-cause death. The RA stiffness index cut-off value associated with an excess event rate was >4.6 on spline curve modeling. Patients with higher RA stiffness index values more often showed advanced NYHA class, of III-IV, (n=81, 34%) than those with a RA stiffness index <4.6 (n=64, 23%, p value 0.01). Conclusion In patients with STR, the RA stiffness index is an important predictor of symptom severity graded according to the NYHA functional class.