Incremental clinical value of the regurgitant fraction assessed by three-dimensional echocardiography in patients with secondary tricuspid regurgitation

Abstract Background Differently from the effective regurgitant orifice area (EROA) and regurgitant volume (RegVol), RegFr directly accounts for the size and the function of the right ventricle (RV). Objectives To assess the relationship between regurgitant fraction (RegFr) evaluated using three-dimensional echocardiography (3DE) and the outcome in patients with secondary tricuspid regurgitation (STR). Methods 331 patients with at least mild STR were enrolled. RegFr was computed as ratio between the RegVol, calculated using the proximal isovolumic surface area (PISA) method by Doppler and the total stroke volume (SV) of the RV computed as difference between 3DE RV end-diastolic (RVEDV) and end-systolic (RVESV) volumes. To compare the association of EROA, RegFr and RegVol with outcome, we used a composite endpoint of heart failure hospitalization (HFH) and death for any cause. Results After a median follow-up of 20 months, 133 patients (40%) reached the combined endpoint. Among the quantitative parameters of STR severity, RegFr had the highest area under the curve at ROC analysis (AUC= 0.65, 95%CI: 0.59-0.71). At Cox regression, RegFr was associated with outcome both in the univariate analysis (HR 1.012, CI 1.003-1.020, p=0.006) and in multivariate, adjusted for several clinical and echocardiography correlates. By testing each single quantitative parameter of STR severity, only RegFr significantly increased the prediction of the basal model (p=0.007) and improved the risk-stratification of the patients on top of EROA (Net Reclassification Index: 0.2833, p=0.011). In the subgroup of patients with non-severe STR (i.e., EROA<0.4 cm²), the RegFr identified the patients with significantly higher risk of events (cumulative incidence of the combined endpoint of 73% in patients with EROA<0.4 cm2 but RegFr≥50% vs 51 % in patients with RegFr<50%, p= 0.02). Conclusions Compared to EROA and RegVol obtained by PISA method, RegFr obtained by 3DE was more strongly associated with the outcome of patients with STR.