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Purpose: Additional pulmonary blood flow (APBF) can provide better pulsating blood flow and systemic arterial oxygen saturation, while low blood pulsation and low oxygen saturation are defects of the Fontan and Glenn procedure. Studying the hemodynamic effect of APBF is beneficial for clinical decisions. This study aimed to explore the effect on particle washout, as well as the differences among the sensitivities of both different hemodynamic parameters and different procedures to APBF., Methods: The patient-specific clinical datasets of a patient who underwent bilateral bidirectional Glenn (BBDG) with APBF were enrolled in this study, and using these datasets, Glenn- and Fontan-type artery models were reconstructed. A series of parameters, including the total caval flow pulsatility index (TCPI), indexed energy loss (iPL), wall shear stress (WSS), systemic arterial oxygen saturation (Sat art ), particle washout time (WOT), pressure in the right superior vena cava (P RSVC ), pulmonary flow distribution (PFD) and hepatic flow distribution (HFD), were computed from computational fluid dynamic (CFD) simulation to evaluate the hemodynamic effect of APBF., Results: The result showed that APBF led to better iPL and Sat art but worse P RSVC and heart load accompanied by a great impact on HFD, making hepatic flow easier to perfuse the side without MPA and APBF. The increase in the APBF rate also effectively results in larger flow pulsation, region velocity, and wall shear stress and lower WOT, and this effect may be more effective for patients with persistent left superior vena cava (PLSVC). However, APBF might have little effect on PFD. Furthermore, APBF might affect WOT, iPL and HFD more significantly than P RSVC and has a greater improvement effect in patients with poorer iPL and WOT., Conclusions: Moderate APBF is not only a measure to promote pulmonary artery growth and systemic arterial oxygen saturation but also an effective method against endothelial dysfunction and thrombosis. However, moderate APBF is patient-specific and should be determined based on hemodynamic preference that leads to desired patient outcomes, and care should be taken to prevent P RSVC and heart load from being too high as well as an imbalance in HFD.

The objective of this study was to compare the effects of different shunt diameters and pulmonary artery (PA) stenosis grades on the hemodynamics of central shunts to determine an optimal surgical plan and improve the long-term outcomes of the operation. A 3D anatomical model was reconstructed based on the patient's clinical CT data. 3D computational fluid dynamics models were built with varying degrees of stenosis (the stenosis ratio α was represented by the ratio of blood flow through the main pulmonary artery to cardiac output, ranging from 0 to 30%; the smaller the value of α , the more severe the pulmonary artery stenosis) and varying shunt diameters (3, 3.5, 4, 4.5, and 5 mm). Our results show that the asymmetry of pulmonary artery flow increased with increasing shunt diameter and α , which will be more conducive to the development of the left pulmonary artery. Additionally, the pulmonary-to-systemic flow ratio ( Q P / Q S ) increases with the shunt diameter and α , and all the values exceed 1. When the shunt diameter is 3 mm and α  = 0%, Q P / Q S reaches the minimum value of 1.01, and the oxygen delivery reaches the maximum value of 205.19 ml/min. However, increasing shunt diameter and α is beneficial to reduced power loss and smoother PA flow. In short, for patients with severe PA stenosis ( α is small), a larger-diameter shunt may be preferred. Conversely, when the degree of PA stenosis is moderate, a smaller shunt diameter can be considered., Competing Interests: The authors declare that they have no conflicts of interest., (Copyright © 2020 Jiawei Liu et al.)

• The hemodynamic effect of nonclosure of Patent ductus arteriosus (PDA) on modified Blalock-Taussig shunt (MBTS) was investigated numerically. • MBTS with nonclosure of PDA plays an active role in preventing early acute shunt failure and produced a better hemodynamic environment including lower blood velocity, energy loss, WSS values at MBT shunt, smaller vortex regions, higher oxygen content (Sao2) and more uniform velocity distribution in the LPA and RPA compared to MBTS with closure of PDA. However, excessive PA flow induced by nonclosure of PDA may result in a series of complication. • MBTS with nonclosure of PDA could be preferred for cases with very low PA overflow risk and maybe benefit for patients with underdeveloped myocardium due to lower energy dissipation. MBTS with closure of PDA could be preferred for cases with very high PA overflow risk. Studying the hemodynamic effects of nonclosure of patent ductus arteriosus (PDA) on the modified Blalock-Taussig shunt (MBTS) is beneficial for surgical PDA management. In the present study, the effect of PDA on MBTS was investigated numerically. A series of parameters including energy loss, wall shear stress (WSS), and left/right Pulmonary artery (LPA/RPA) flow ratio were computed from simulations to analyze the hemodynamic effects of PDA on MBTS. To ensure the universality of the research conclusions, three typical models, including models with a well-developed RPA, a symmetrically-developed pulmonary artery(PA) and a well-developed LPA, were constructed based on patient-specific pre-surgery clinical data sets. A commercial CFD solver ANSYS-Fluent software was adopted for this study. A pressure-based solver for incompressible Newtonian flows, the K-omega based shear-stress-transport model and a second-order accurate numerical discretization scheme were employed for simulation. Our results show that MBTS with nonclosure of PDA is accompanied by lower blood velocity, energy loss and WSS values at the MBT shunt; smaller vortex regions; higher oxygen content(Sao 2) and PA flow; and more uniform velocity distribution in the LPA and RPA than MBTS with closure of PDA. If the PDA was not closed when performing primary MBTS, a series of hemodynamic changes occurs during PDA closure in postoperative recovery: the energy loss, PA flow and Sao 2 decrease, while the oxygen delivery(Do2) and WSS values at the MBT shunt increase. Nonclosure of PDA could provide a better hemodynamic environment and play an active role in preventing early acute shunt failure. It could be preferred for cases with very low PA overflow risk and may benefit patients with an underdeveloped myocardium due to its lower energy dissipation than PDA closure. However, excessive PA flow induced by nonclosure of PDA may result in a series of complications. Surgeon's decision-making process with respect to PDA management should consider the individual patient to achieve optimal postoperative recovery. [ABSTRACT FROM AUTHOR]