Improving the quantitative assessment of tricuspid regurgitation severity by establishing new threshold values for the corrected proximal isovelocity surface area method

Abstract Introduction The correction of the proximal isovelocity surface area (PISA) method has been reported to improve the accuracy of assessing the severity of secondary tricuspid regurgitation (STR)1. It has been demonstrated that correcting the conventional PISA method by the angle formed by the tethered tricuspid leaflets and the regurgitant velocity yields larger values for both regurgitant volume (RegVol) and effective regurgitant orifice area (EROA)1. However, it remains unclear whether new threshold values are necessary for the corrected PISA method to effectively categorize TR severity. Purpose To identify threshold values for EROA and RegVol measured by the corrected PISA method for a three-grade STR severity grading scheme. Methods We used 3D echocardiography to determine the volumetric regurgitant fraction (3DERegFr), calculated as the difference between the left and right ventricular (RV) stroke volumes (SV) divided by the RV SV, in a cohort of 208 consecutive patients (77± 12 years; 62% women) with isolated STR. Based on 3DERegFr, we classified TR severity into mild (3DERegFr 30%), moderate (3DERegFr 30-49%), and severe (3DERegFr 49%). We then measured EROA and RegVol using both conventional (EROA and REgVol) and corrected (EROAc and RegVolc) PISA methods, and made comparisons. The threshold values for the EROAc and the RegVolc to distinguish between adjacent TR severity grades were determined using a non-parametric approach rooted on kernel density estimate intersections (Figure 1). We conducted pairwise comparisons between severity grades, with the values of EROAc or RegVolc at the intersections indicating the optimal threshold values. Classification accuracy were compared using Cochran’s Q test and a p value 0.05 was considered statistically significant. Results The threshold value for identifying patients with mild, moderate and severe TR, as per 3DERegFr classification, were 0.29 cm², 0.29-0.51 cm², and 0.51 cm² for EROAc, respectively; and 25 mL, 25-44 mL, and 44 mL for RegVolc, respectively. The accuracy of these new threshold values in predicting the TR severity based on 3DERegFr was 76% for both EROAC and RegVolc (Figure 1), and it was significantly higher than accuracy of EROA (67%, p=0.002) and RegVol (64%, p=0.007) (Figure 2). In comparison to the guideline-recommended EROA cut-offs (0.20 cm² and 0.40 cm²), the EROAc thresholds were higher for both moderate and severe TR, suggesting that the conventional EROA cut-offs consistently underestimate TR severity across all grades. Conversely, when compared to the guideline-recommended RegVol cut-offs (30 mL and 45 mL), the RegVolc thresholds were lower for moderate TR (25 mL) and similar for severe TR (44 mL), indicating that the conventional RegVol cutoffs tend to underestimate moderate STR. Conclusion New threshold values for the corrected PISA method must be considered to improve the classification of STR severity.Figure 1 Figure 2