4D-Flow MRI Characterization of Pulmonary Flow in Repaired Tetralogy of Fallot

Featured Application Repaired Tetralogy of Fallot pulmonary hemodynamic alterations can be characterized by 4D-flow MRI. Patients with Tetralogy of Fallot (TOF) have multiple surgical sequelae altering the pulmonary flow hemodynamics. Repaired TOF (rTOF) adults frequently develop pulmonary regurgitation impacting the blood flow pressure, right ventricle load, and pulmonary hemodynamics. We aimed to evaluate the pulmonary flow hemodynamics using 4D-flow magnetic resonance imaging (MRI) for characterizing altered blood flow, viscous energy loss (EL), wall shear stress (WSS), pressure drop (PD), and ventricular flow analysis (VFA) in rTOF patients. We hypothesized that 4D-flow based parameters can identify pulmonary blood flow alterations. A total of 17 rTOF patients (age: 29 +/- 10 years, 35% women) and 20 controls (age: 36 +/- 12 years, 25% women) were scanned using a dedicated cardiac MRI protocol. Peak velocity and regurgitant fraction were significantly higher for rTOF patients (p < 0.001). WSS was consistently elevated along the PA in the rTOF (p <= 0.05). The rTOF average circumferential WSS was higher than axial WSS at the main pulmonary artery (p <= 0.001). PD and EL were consistently higher in the rTOF as compared with controls (p < 0.05). For VFA, delayed ejection increased and retained inflow decreased in rTOF patients (p < 0.001). To conclude, this study demonstrated that 4D-flow MRI pulmonary flow in the rTOF can exhibit altered peak velocity, valvular regurgitation, WSS, EL, PD, and VFA.

Automated summary

4D-flow MRI can be used to evaluate pulmonary flow hemodynamics in repaired Tetralogy of Fallot (rTOF) patients. The study found that rTOF patients had significantly higher peak velocity and regurgitant fraction, elevated wall shear stress (WSS) along the main Pulmonary Artery (PA), higher WSS in circumferential direction at the PA, as well as higher pressure drop (PD) and viscous energy loss (EL). Ventricular flow analysis showed delayed ejection and decreased retained inflow in rTOF patients. These findings demonstrate that 4D-flow MRI can reveal pulmonary flow alterations in rTOF patients.