ABSTRACT
Objective Modified B-T shunt (MBTS) and central shunt (CS) are two common surgical procedures for the treatment of tetralogy of fallot (TOF). The purpose is to analyze and compare the hemodynamic features of MBTS and CS. Methods 3D anatomy was reconstructed by medical images obtained from a patient with TOF, and two computational models were generated through virtual operations. A lumped parameter model was constructed to predict the post-operational boundary conditions. Computational fluid dynamics (CFD) was performed for the two models. Results A persistent pulmonary blood perfusion was observed in each model both during the systolic phase and diastolic phase, but the maximum velocities in the shunt were different for the two models. The pressure drop of the shunt in CS model was higher than that in MBTS model. The wall shear stress of the shunt in the MBTS model ranged unevenly from 0.025 to 340 Pa, while the wall shear stress in CS model ranged relatively evenly from 32.2 to 72.6 Pa. Conclusions Pulmonary artery blood was increased effectively for both options. The blood perfusion of right upper extremity was decreased in the MBTS model. More blood was directed into the pulmonary artery in CS model. Attention should be paid to the fact that the pressure gradient was large at the proximal anastomosis in both models in clinic. This study provides important theoretical references for surgeons to make choice from the surgery options in the treatment with TOF.
ABSTRACT
Objective To study the hemodynamics of central shunt (CS) by numerical simulation and investigate the effects of the elastic and rigid vessel wall on distributions of hemodynamic parameters in the vessel. Methods Two idealized CS models were constructed, one with a rigid wall (the rigid model) and the other with an elastic wall (the elastic model). Numerical calculation was conducted by the finite element method, and the elastic model adopted the fluid structure interaction. Results The distribution of flow velocity and pressure in both models were generally the same. About 68.9% of the aortic blood was directed into the pulmonary artery for the rigid model, as compared to 70% for the elastic model. The pressure drops within the shunt for the elastic model and rigid model were about 7.668 8 kPa and 7.222 3 kPa, respectively. The maximum variation in the average cross sections along the shunt was about 2.2% for the elastic model, appearing at the proximal end to side (ETS) anastomosis. The maximum difference of wall shear stress (WSS) between the two models at five key regions of each was about 16.1%. Conclusions Generally, the global flow structure in both the CS models remains unchanged; the elasticity of the vessel wall slightly influenced the flow distributions and pressure drop of the shunt; the effect from elasticity of the vessel wall on average cross sections along the shunt was higher at the proximal ETS anastomosis than that at the distal ETS anastomosis; the hypothesis that the vessel wall is rigid is acceptable in CS numerical simulations for the treatment of tetralogy of Fallot (TOF). However, the coupling of flow dynamics and wall mechanics may lead to a more reliable simulation result in the CS.