MRI Assessment of Energy Loss Within the Thoracic Aorta and Its Impact on Cardiac Function in Fontan Patients After Aortic Reconstruction.

Abstract

Background: In Fontan patients undergoing aortic reconstruction, concerns regarding the impact of aortic function on ventricular function exist.

Purpose: 4D Flow MRI was used to compare energy loss (EL) within the thoracic aorta in patients with and without aortic reconstruction.

Study type: Retrospective case control.

Population: Eighty-nine patients underwent 4D Flow MRI: group A (n = 36), Fontan patients without aortic reconstruction (9.9 (1.0-26.7) years since Fontan completion); group B (n = 42), Fontan patients with aortic reconstruction (11.8 (1.0-26.4) years since Fontan completion); and group C (n = 11), patients with biventricular circulation without aortic reconstruction.

Field strength/sequence: Balanced SSFP cine and time-resolved 3D phase contrast (4D Flow) sequences at 1.5 T or 3 T.

Assessment: Peak and average aortic EL in the thoracic aorta as well as peak aortic velocity and flow volume were assessed. Correlations between EL indexed to aortic forward flow volume and volumetric ventricular parameters and peak aortic velocity were assessed.

Statistical tests: Kruskal-Wallis test, chi-square test and Spearman's correlation coefficient were used.

Results: Peak and average EL were significantly larger in group B than in groups A and C (peak EL (mW); A: 1.45 (0.22-9.81), B: 3.09 (0.51-12.49), C: 2.10 (1.20-3.45); average EL (mW); A: 0.46 (0.07-2.63), B: 1.13 (0.13-4.67), C: 0.76 (0.40-1.98)). Group B had significantly larger ventricular end-diastolic volume index (EDVi, 108 mL/m²) and end-systolic volume index (ESVi, 53 mL/m²), significantly lower ejection fraction (EF, 51%) and significantly greater end-diastolic myocardial mass (MM, 50 g/m²) of the systemic ventricle than group A (EDVi: 86 mL/m², ESVi: 34 mL/m², EF: 58%, end-diastolic MM: 43 g/m²). In Fontan patients, indexed average aortic EL correlated positively with aortic peak velocity (R = 0.68) and with years after Fontan completion (R = 0.60).

Data conclusion: Fontan patients who underwent aortic reconstruction had increased aortic EL, even in the absence of significant residual aortic stenosis.

Evidence level: Level 3.

Technical efficacy: Stage 3.