Redefining the assessment of secondary tricuspid regurgitation based on novel 3D parameters: an echocardiographic approach to risk stratification

Background Accurate quantification of secondary tricuspid regurgitation (STR) remains challenging. Although effective regurgitant orifice area (EROA) and regurgitant volume (RegVol) derived from the corrected proximal isovelocity surface area (PISA) method improved grading, this approach relies on geometric and haemodynamic assumptions often unmet in STR. Three-dimensional echocardiographic volumetric methods (3DE-VM), avoiding geometric assumptions and Doppler limitations, may provide a more robust assessment, but outcome-based thresholds are lacking. Purpose To: (i) derive three-dimensional RegVol (3DE-RegVol) and EROA (3DE-EROA); (ii) define outcome-based thresholds for mild, moderate, and severe STR; and (iii) compare their prognostic performance with corrected PISA. Methods We retrospectively included 304 patients (76±9 years; 57% women) with isolated STR. 3DE-RegVol was calculated as the difference between right and left ventricular stroke volumes. 3DE-EROA was obtained by dividing 3DE-RegVol by the tricuspid regurgitation velocity–time integral. The primary endpoint was all-cause mortality or heart failure hospitalization. Results Outcome-based thresholds for moderate and severe STR were 15 mL and 36 mL for 3DE-RegVol, and 0.20 cm² and 0.45 cm² for 3DE-EROA. These cut-offs stratified patients with progressively lower 3-year survival (log-rank P<0.001). Agreement between 3DE-RegVol and corrected PISA RegVol was moderate (62%; κ=0.64), with PISA more frequently assigning higher severity grades. Prognostic discrimination was superior with 3DE-RegVol (C-statistic 0.67 vs. 0.65). Patients classified as severe by 3DE but moderate by PISA had significantly worse outcomes (Figure 1). Agreement between 3DE-EROA and PISA EROA was also moderate (κ=0.62), with PISA systematically overestimating severity. 3DE-EROA showed improved prognostic discrimination (C-statistic 0.653 vs. 0.633) and more accurate risk stratification in discordant cases (Figure 2). Conclusions The 3DE volumetric method is feasible and provides outcome-based thresholds for STR severity with improved prognostic accuracy compared with corrected PISA. Integration of 3DE volumetric assessment may enhance risk stratification in isolated STR.