PORTAL VENOUS HEMODYNAMIC ANALYSIS UNDER FONTAN CIRCULATION USING 4D-FLOW MRI (RF_TH_180)

 Fontan operation is functional surgery for single ventricular morphology. Fontan-associated liver disease (FALD) is known as a mid- to long-term complication after Fontan operation. The purpose of this study was to devise a new index for evaluating FALD using portal vein hemodynamic analysis using 4D-flow MRI.

Methods:

We imaged the portal vein main trunk of Fontan postoperative patients and healthy subjects using 4D-flow MRI at Sakakibara Heart Institute, and measured kinetic energy (KE; unit: mJ/mL) and energy loss (EL; unit: mW/mL), wall shear stress (WSS; unit: Pa), and helicity (unit: m⁴/s^-2), which is an index of the strength of spiral blood flow, were measured. KE and EL were standardized by dividing by the portal vein main lumen volume, and helicity was defined as a vector quantity for clockwise and counterclockwise spirals and was used as the sum value. The average value of all parameters within one cardiac cycle was calculated, and the portal vein hemodynamics after Fontan operation was evaluated. 4D-flow analysis was performed with iTFlow2.1 manufactured by Cardio Flow Design, Japan.

Results:

4D-flow MRI of the main trunk of the portal vein was performed on 15 patients (F group; 18.6 +/- 5.0 years old) after Fontan operation and 8 healthy subjects (N group; 31.5 +/- 4.9 years old). Diagnosis in Group F was double outlet right ventricle in 5 cases, pulmonary atresia with an intact ventricular septum in 4 cases, and single right ventricle, tricuspid atresia, and transposition of great arteries in 2 case each. Total cavopulmonary connection without fenestration as Fontan operation was performed in all cases, and CVP was 9.8 +/- 2.4 mmHg. KE was higher in the N group with a significant difference (F vs. N; 3.39E-03 +/- 1.40E-03 vs. 4.95E-03 +/- 8.89E-04, p</span>＜0.05). EL and WSS were higher in group F; however, no significant difference was observed. Helicity (F vs. N; 3.88E-06 +/- 1.61E-06 vs. 6.85E-06 +/- 5.87E-07, p</span>＜0.01) was significantly higher in the N group, furthermore, both groups had a lot of counterclockwise spiral flow. KE was found to be correlated with EL (r=0.8) and WSS (r=0.7), and EL was found to be weakly correlated with CVP (r=0.56).

Conclusion:

Although the number of cases was small, the portal vein circulation after Fontan operation had lower kinetic energy than that of healthy subjects. On the other hand, it was speculated that the reason why helicity is high in healthy subjects is that spiral flow is difficult to form in the portal vein of Fontan circulation. In the future, we would like to increase the number of cases and perform detailed studies to establish the usefulness of portal vein 4D-flow MRI in the evaluation of FALD.

Portal vein 4D-flow

Portal vein 4D-flow