Aims: In clinical practice, severity of tricuspid regurgitation (TR) is commonly graded by transthoracic (TTE) or transesophageal (TOE) echocardiography. However, due to methodological limitations the accuracy of echocardiographic parameters to quantify TR, such as vena contracta (VC) or proximal isovelocity surface area (PISA) assessment, has been questioned. In addition, the value of TTE/TOE methods to characterize TR severity following transcatheter tricuspid valve edge-to-edge repair (TTVR) is unclear. The present study aimed to validate echocardiographic indices of TR severity against cardiac magnetic resonance imaging (cMRI) in the context of TTVR.

Methods: A derivation cohort of 48 patients (77±5 years of age, 47% female) undergoing TTE/TOE and cMRI before, 1 month and 6 months after TTVR was retrospectively identified in a single-center analysis. In these patients, currently recommended echocardiographic indices of TR severity (biplane VC, effective regurgitant orifice area and regurgitant volume according to PISA, velocity of systolic flow reversal in hepatic veins, continuous wave TR Doppler signal, TR jet area, TR jet area/right atrial area, 3D VC area) were compared against TR fraction obtained by volumetric and flow analyses on cMRI. The prognostic implications of postprocedural 3D VC area assessment were characterized in a validation cohort of 153 TTVR patients.

Results: Before TTVR, recommended echocardiographic parameters exhibited statistically significant, but modest correlations with TR fraction obtained on cMRI in the derivation cohort. Strongest correlations with cMRI-derived TR fraction were observed for 3D VC area (r = 0.83, P<0.01), velocity of systolic flow reversal in hepatic veins (r = 0.78, P<0.01) and EROA according to PISA (r=0.71, P>0.01). A reduction in TR by at least one grade according to a five-tiered grading system was achieved in 89% of patients during TTVR and 75% of patients had a postprocedural TR grade of 2 or less. Following TTVR, only 3D VC area significantly correlated with cMRI-derived TR fraction (r = 0.78, P<0.01, after 1 month and r = 0.76, P<0.01, after 6 months), whereas all other echocardiographic parameters analyzed did not provide a meaningful estimate of residual TR. In the validation cohort of 153 patients analyzing the predictive value of echocardiographic TR estimates for clinical outcome following TTVR, 3D VC area but not conventional 2D echocardiographic indices of TR severity served as an independent predictor of symptomatic improvement and a combined endpoint of all-cause mortality and heart failure hospitalizations.

Conclusion: The findings of the present study suggest for the first time that the clinical value of 2D echocardiographic parameters to assess residual TR following TTVR is limited. Instead, VC area derived from 3D echocardiographic imaging is the only parameter to reliably quantify TR severity following TTVR and is associated with symptomatic and clinical outcome on follow-up after TTVR. These findings have important implications for the care of patients with symptomatic TR considered for interventional treatment.