Abstract
We used 4D-flow MRI to investigate circulation, an area integral of vorticity, in the main pulmonary artery (MPA) as a new hemodynamic parameter for assessing patients with a repaired Tetralogy of Fallot (TOF). We evaluated the relationship between circulation, right ventricular (RV) function and the pulmonary regurgitant fraction (PRF). Twenty patients with a repaired TOF underwent cardiac MRI. Flow-sensitive 3D-gradient sequences were used to obtain 4D-flow images. Vortex formation in the MPA was visualized, with short-axis and longitudinal vorticities calculated by software specialized for 4D flow. The RV indexed end-diastolic/end-systolic volumes (RVEDVi/RVESVi) and RV ejection fraction (RVEF) were measured by cine MRI. The PR fraction (PRF) and MPA area were measured by 2D phase-contrast MRI. Spearman ρ values were determined to assess the relationships between circulation, RV function, and PRF. Vortex formation in the MPA occurred in 15 of 20 patients (75%). The longitudinal circulation (11.7 ± 5.1 m2/s) was correlated with the RVEF (ρ = − 0.85, p = 0.0002), RVEDVi (ρ = 0.62, p = 0.03), and RVESVi (ρ = 0.76, p = 0.003) after adjusting for the MPA size. The short-axis circulation (9.4 ± 3.4 m2/s) in the proximal MPA was positively correlated with the MPA area (ρ = 0.61, p = 0.004). The relationships between the PRF and circulation or RV function were not significant. Increased longitudinal circulation in the MPA, as demonstrated by circulation analysis using 4D flow MRI, was related to RV dysfunction in patients with a repaired TOF.
Highlights
Pulmonary regurgitation (PR) is the most common complication after repaired Tetralogy of Fallot (TOF)
A patch infundibuloplasty was performed in 9 of 20 patients (45%); transannular patch repair was performed in 6 patients (30%); pulmonary valve replacement was performed in 2 patients (10%); and conotruncal repair, muscle resection, and Rastelli procedure were each performed in 1 patient (5% each)
Four-dimensional flow imaging showed variations in the outflow from the right ventricular (RV) to the main pulmonary artery (MPA) in patients repaired by various surgical procedures
Summary
Pulmonary regurgitation (PR) is the most common complication after repaired Tetralogy of Fallot (TOF) It induces right ventricular (RV) volume overload, which leads to RV dilation and eventually RV d ysfunction. One reason for an underestimation of the PRF is the presence of backward flow within a systole that is affected by turbulence or stagnation due to the dilation or stenosis of the pulmonary artery (PA) in patients after repair of the T OF3. Flow patterns of the main pulmonary artery (MPA) in patients with a repaired TOF are characterized by increased helical or vortical flow features, there are many variations because of PA dilation and stenosis. The purpose of this study was to investigate circulation analysis in the MPA by 4D flow MRI for assessment of MPA in patients after repair of the TOF by evaluating the relationship of vortex formation with RV function and PRF
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