4D Flow MRI-Based Quantification of Tricuspid Regurgitation: A Possible Approach to Improve Measurement Repeatability.

PURPOSE: To address limitations in tricuspid regurgitation (TR) quantification by magnetic resonance imaging (MRI) or transthoracic echocardiography (TTE), a new method is proposed to directly quantify TR volume (TRV) using 4D Flow MRI with retrospective tricuspid valve (TV) annular tracking.

METHODS

Thirty patients with TR were prospectively enrolled. TRV was quantified using four MRI-based methods: (i) indirect, (ii) direct (2D phase-contrast), (iii) 4D Flow with a static TV plane, and (iv) 4D Flow with dynamic annular tracking. Reproducibility and agreement were assessed in terms of TR grading against standard MRI- and TTE-based methods.

RESULTS

The dynamic 4D Flow method correlated strongly with all other MRI methods (r = 0.77-0.81, p < 0.0001) but consistently yielded higher TRV values. Compared with the indirect method, it showed a Bland-Altman bias of 16 mL (limits of agreement: -19 to 51 mL), along with the highest agreement (intraclass correlation coefficient of 0.88). Agreement in TR severity grading was poor across methods (kappa ≤ 0.07), with dynamic 4D Flow classifying more cases as moderate or severe. Agreement with TTE was slight (kappa = 0.17, p = 0.27) with concordant TR grading in 50% of patients. Inter-observer reproducibility was excellent (r = 0.99, bias = 0.7 mL, kappa = 0.80).

CONCLUSION

4D Flow with dynamic TV tracking offers a reproducible and potentially more sensitive method for TRV quantification than conventional MRI techniques. Despite limited alignment with TTE, this technique may help overcome key imaging limitations and improve TR clinical evaluation, especially in complex cases.