Effect of modified Blalock-Taussig shunt anastomosis angle and pulmonary artery diameter on pulmonary flow

OBJECTIVE: This study aimed to identify the best graft-to-pulmonary artery (PA) anastomosis angle measuring pulmonary blood flow, wall shear stress (WSS), and shunt flow. METHODS: A tetralogy of Fallot with pulmonary atresia computer model was used to study three different modified Blalock-Taussig shunt (mBTS) anastomosis angle configurations with three different PA diameter configurations. Velocity and WSS were analyzed, and the flow rates at the right PA (RPA) and left PA (LPA) were calculated. RESULTS: A 4-mm and 8-mm diameter of RPA and LPA, respectively with vertical shunt angle produces the highest total flow. In the RPA larger diameter than the LPA configutations, the left-leaning shunt produces the lowest total PA flow whereas in the LPA larger diameter than the RPA configuratios, the right-leaning shunt produces the lowest total PA flow. Therefore, the shunt anastomosis should not be leaned through the narrow side of PA to reach best flow. As the flow inside the shunt increased, WSS also increased due to enhanced velocity gradients. CONCLUSION: The anastomosis angle between the conduit and PA affects the flow to PA. Vertical anastomosis configurations increase the total PA flow; thus, these configurations are preferable than the leaned configurations.