The end-systolic right atrial to right ventricular volume ratio - differentiation threshold and added diagnostic value to identify the atrial phenotype of the secondary tricuspid regurgitation
Authors: Clement A , Muraru D , Fisicaro S , Penso M , Tomaselli M , Radu N , Delcea C , Gavazzoni M , Rella V , Buta A S , Sascau R A , Badano L P 
Published: January 2025

Abstract

Introduction
Secondary tricuspid regurgitation (STR) is currently classified into atrial (A-STR) and ventricular (V-STR) phenotypes. In the multiparametric definition framework of A-STR, an end-systolic (ES) right atrial (RA) to right ventricular (RV) volume ratio ≥1.5 has been proposed among the criteria that favor the diagnosis of A-STR over V-STR. However, no previous study has tested or validated this specific cut-off value.

Purpose
We aimed to determine the threshold value of the ES RA:RV volume ratio for distinguishing A-STR and V-STR in a large cohort of STR patients evaluated with three-dimensional echocardiography (3DE).

Methods
Consecutive patients with a first diagnosis of STR (ranging from mild to severe) who underwent complete 3DE evaluation were included in the study.

Results
350 patients (75±13 years, 65% women, 59% with severe STR) were included in the final cohort. Even though patients with A-STR and V-STR displayed similar STR severity and comparable RA size, the ES RA:RV volume ratio was significantly higher in A-STR than in V-STR (1.75 [interquartile range (IQR) 1.35-2.45] vs. 1.18 [IQR 0.81-1.66], respectively; p&lt;0.001). On receiver operating characteristic (ROC) analysis, the ES RA:RV volume ratio exhibited a significantly higher predictive power for the A-STR diagnosis [Area under the curve (AUC) 0.73, 95% CI 0.68-0.78] compared to RA maximum volume (AUC 0.6, 95% CI 0.54–0.66, p=0.01), RA minimum volume (AUC 0.59, 95%CI 0.53–0.65, p=0.007), and RA minimum volume: RV end-diastolic volume ratio (AUC 0.57, 95%CI 0.51-0.63, p&lt;0.001) (Figure 1). Additionally, in ROC analysis, the cut-off value of ES RA:RV volume ratio that most effectively differentiated between A-STR and V-STR, yielding the highest AUC (0.68, 95% CI 0.63–0.73) was 1.40. In single-variable logistic regression analyses, the ES RA:RV volume showed a significant association with the A-STR phenotype [Odds ratio (OR) 2.96, 95% CI 2.14 – 4.23, p&lt;0.001]. However, a multivariable model which included ES RA:RV volume ratio, left ventricular (LV) ejection fraction, RV ejection fraction, RA maximum volume, and pulmonary artery systolic pressure (PASP) resulted in an AUC= 0.97 to differentiate between the A-STR and the V-STR phenotypes. Ultimately, the additive diagnostic utility of the ES RA:RV volume ratio was assessed in a hierarchical model χ² analysis, wherein the addition of the ES RA:RV volume ratio to a model including LV ejection fraction, RV ejection fraction, RA maximum volume, and PASP improved the model, strengthening the prediction for the A-STR phenotype (Figure 2).

Conclusions
ES RA:RV volume ratio ≥1.4 favors A-STR over V-STR. This echocardiographic parameter should be consistently evaluated and reported in STR patients due to its increased diagnostic power.
Figure 1.
Figure 2.