Comparison of 2D and 4D Flow MRI Measurements for Hemodynamic Evaluation of the Fontan Palliation

Background:The assessment of Fontan circuit’sflow is traditionally evaluated by multiple through-plane phase-contrast MRI acquisitions(2Dflow),while recently,a single volumetric 4D-flow MRI acquisition is emerging as a comprehensive tool for the hemodynamic evaluation in congenital heart diseases.Purpose:To compare 2D and 4D-flow MRI measurements in patients after Fontan palliation and to evaluate parameters affecting potential dis-agreement.Methods:39 patients after Fontan palliation(23 males,age 22±11 years)who underwent cardiac MRI with 2D and 4D-flow MRI acquisition were included in the study.In all patients,bloodflow quantification in the Fontan circuit and aorta by 2Dflow and by 4Dflow MRI acquisition blinding to the 2D results was per-formed.The agreement between 2D and 4D-flow MRI was calculated as the intraclass correlation coefficient(ICC).The mean absolute differences between 4D and 2Dflows were analyzed using linear regression models.Results:4D-flow MRI acquisition time was slightly lower than 2D(7.6±1.8 min vs.9.4±3.3 min,p=0.03).Flow was slightly predominant in the right pulmonary artery(58%of total pulmonaryflow).Conduit/tunnel-pul-monary arteriesflow accounted for 60%of the Fontan circuit.Agreement between 2D and 4D was overall good-to-excellent from ICC:0.81795%CI:0.637–0.907 to 0.93295%CI:0.866–0.965.There was no significant influ-ence of evaluated parameters on the agreement on 4D and 2Dflow.Conclusions:4D-flow MRI represents a valid tool in Fontan’sflow quantification.Further larger studies are needed to confirm our results and to evaluate the impact of advanced 4D-flow MRI parameters on the prognostic stratification in patients after Fontan palliation.