Quantification of tricuspid valve regurgitation in patients with Ebstein's anomaly: evaluation of different methods with 2D-phase contrast and 4D-flow CMR

Background: Ebstein's anomaly (EA) is a congenital heart disease involving a dysplasia of the tricuspid valve (TV), right atrium and right ventricle. Its imaging hallmark is the apical displacement of the septal leaflet of the TV. A severe tricuspid regurgitation (TR) is common in this population and the surgical correction of this condition aims to minimize TR. Several methods are used to quantify the regurgitant volume (RVol). 4D-flow cardiac magnetic resonance (CMR) is now part of the daily clinical practice in congenital heart disease for the quantification of valvular regurgitations or shunts. However, data on the evaluation of TR in patients with EA is scarce. Our aim was to evaluate different methodology in 4D-flow CMR to quantify TR in adult with EA.

Methods: Clinical and CMR data including 4D-flow of 31 patients with EA where retrospectively analysed. The tricuspid RVol was assessed with three different methods: first, the 2D-indirect method consisted in the subtraction of the systolic forward volume through the main pulmonary artery acquired with 2D-phase contrast from the functional right ventricle (fRV) stroke volume calculated with the systolic and diastolic difference of fRV volume with Simpson’s method on short axis steady-state free-precession 2D-images stack. Second the 4D-indirect method consisted in the subtraction of the systolic forward volume through the main pulmonary artery acquired with 4D-flow from the diastolic forward volume through the TV tracked along the cycle with 4D-flow. Third, the RVol was directly measured in the systolic regurgitant jet in right atrium using 4D-flow. Schematic explanation and CMR examples of the methods can be found the Figure 1 and 2A, respectively. The reference method was defined as the mean value of those three methods. Linear regression was performed for each of the three methods with the reference method as well as for each method and the fRV end diastolic volume (fRVEDV).

Results: Baseline characteristics can be found in the Figure 2B. Linear regression yielded the following results: 4D-direct vs 4D-indirect: r=0.82, p=< 0.001; 4D-direct vs 2D-indirect: r=0.87, p=< 0.001; 4D-indirect vs 2D-indirect: r=0.79, p=< 0.001; 2D-indirect vs mean of the three methods: r=0.93, p=< 0.001; 4D-indirect method vs mean of the three methods: r=0.93, p=< 0.001; 4D-indirect method vs mean of the three methods, r:0.95, p=< 0.001; Bland altman and linear regression can be found in Figure 3. The linear regressions between fRVEDV and the different RVol quantification methods were as follows: 2D-indirect vs fRVEDV: r=0.44, p=< 0.001; 4D-indirect method vs fRVEDV: r=0.33, p=< 0.001; 4D-direct method vs fRVEDV, r=0.51, p=< 0.001 and mean of three methods vs fRVEDV, r=0.49, p=< 0.001.

Conclusion: The best agreement with the reference method was found for the 4D-direct method. The assessment of the RVol through the direct measurement the regurgitant jet seems to be promising and paves the way for its evaluation in larger cohort with long-term follow-up.

Description of the RVol quantification methods
A. Example of RVol quantification methods. B. clinical and CMR data
RVols: Bland-Altman and linear regressions