Refining the assessment of moderate secondary tricuspid regurgitation: an echocardiographic approach to risk stratification

Background Moderate secondary tricuspid regurgitation (STR) is independently associated with increased mortality (1), underscoring the need for accurate severity assessment. According to current recommendations, moderate STR is defined by a regurgitant fraction (RegFr) between 16% and 49%, a broad range that likely encompasses patients with different clinical risk (2). Recent evidences suggest that further subclassifying moderate STR into ‘mild-moderate’ and ‘moderate-severe’ may improve prognostic stratification and better guide therapeutic decisions for those undergoing either transcatheter repair or surgical treatment (3). Nevertheless, an echocardiographic risk-based stratification of moderate STR has not been proposed. Purpose Accordingly, we sought to: i) identify the RegFr threshold value associated with an increased risk of a composite endpoint of all-cause mortality and hospitalization for heart-failure in moderate STR; ii) based on the RegFr associated with increased risk for excessive adverse events identified, to derive the threshold values for effective regurgitant orifice area (EROACORR ) and regurgitant volume (RegVolCORR ) measured by the corrected PISA method to further stratify moderate STR into mild- moderate and moderate-severe subgroups. Methods We used three-dimensional echocardiography to determine the volumetric RegFr, calculated as the difference between the right (RV) and left ventricular (LV) stroke volumes (SV) divided by the RVSV. A total of 98 patients (78±9 years; 55% women) with isolated moderate STR were enrolled. Results After a mean follow-up period of 50±39 months, 26 patients reached the composite endpoint. On spline-curve modeling, the threshold value associated with an excess event rate among patients with moderate STR was 27%. After multivariate adjustment for age, NYHA functional class, RV and LV ejection fraction, and pulmonary artery systolic pressure, a RegFr >27% remained independently associated with a higher risk of composite endpoint (HR = 2.59; 95% CI: 1.32–5.07; p = 0.004). On Kaplan-Meier analyses, when dividing the overall cohort according to the threshold value identified on spline curve modeling, patients with moderate STR and RegFr> 27% showed a significantly higher rate of the composite endpoint (event rate at 2 years 29%±4% vs 16%±3 %, log-rank<0.0001) (Figure 1). Accordingly, the cohort was further divided into mild-moderate STR (RegFr 16%–26%, n=36) and moderate-severe STR (RegFr 27%–49%, n=62). The threshold values of EROACORR and RegVolCORR to identify patients with mild-moderate, and moderate-severe STR were 0.30 cm² and 28 mL, respectively (Figure 2). Conclusions A more granular stratification of moderate STR into ‘mild-moderate’ and ‘moderate- severe’ may reflect underlying differences in clinical risk and support more tailored therapeutic decisions for patients considered for intervention.