Assessing the severity of tricuspid regurgitation (TR) is crucial for determining patient prognosis,1, 2, 3, 4 selecting the most effective treatments,5,6 and evaluating the outcomes of surgical and transcatheter interventions.7 To achieve these goals, quantifying TR should always be prioritized, especially when moderate or more severe TR is suspected.8,9

Current guidelines recommend using the proximal isovelocity surface area (PISA) method to calculate the effective regurgitant orifice area (EROA) and the regurgitant volume (RegVol).8,9 However, the PISA method has several limitations that may result in a systematic underestimation of TR severity in up to 30% of patients.10,11 Adjustments to the PISA method, which incorporate parameters accounting for leaflet tethering angles and the low velocity of the regurgitant jet, have reduced this underestimation and improved the correlation between corrected EROA and clinical outcomes.12 Nevertheless, limitations persist, including (1) flattening of the PISA shell contour, which can result in a smaller PISA radius; (2) the noncircularity and unpredictable shape of the TR orifice (e.g., star-shaped, elliptical, slit-like); and (3) the dynamic nature of TR throughout the systolic phase that is not accounted for in EROA calculations based on measurements from a single frame. Additionally, the PISA method cannot be used to assess residual TR following tricuspid transcatheter edge-to-edge repair procedures.

The Doppler volumetric method has been proposed to address the limitations of the PISA method.13 Although this method also relies on geometrical assumptions about the shape of the tricuspid annulus, requiring further validation, the principle of volumetric quantification of the RegVol—by measuring the total right ventricular (RV) stroke volume (SV), which combines both forward SV and RegVols and then subtracts the forward SV—is physiologically sound.9

Advancements in computational power and probe design have transformed three-dimensional echocardiography (3DE) from a research tool into a clinically valuable technique. Three-dimensional echocardiography can accurately measure the SV of both the left ventricle (LV) and right ventricle (RV), allowing for the calculation of tricuspid RegVol in patients with no or mild mitral or aortic regurgitation by subtracting the left ventricular (LV) SV from the RV SV.11,14 This method helps address the limitations of the Doppler technique and remains effective after transcatheter or surgical interventions to repair or replace the tricuspid valve. However, the volumetric method using 3DE to calculate TR RegVol has yet to be validated.

Thus, the present study aimed to (1) invasively validate the tricuspid RegVol calculated by the 3DE volumetric method and (2) compare the quantitative metrics used to assess the severity of TR derived from 3DE RegVol with those obtained from the conventional and the corrected PISA methods.