Numerical Simulation of a Realistic Total Cavo-pulmonary Connection: Effect of Unbalanced Pulmonary Resistances on Hydrodynamic Performance

Abstract

Total cavo pulmonary connection (TCPC) is one of the surgical techniques adopted to compensate the failure of the right heart in pediatric patients. The main goal of this procedure is the realization of a configuration for the caval veins and for the pulmonary arteries that can guarantee as low as possible pressure losses and appropriate lung perfusion. Starting from this point of view, a realistic TCPC with extracardiac conduit (TECPC) is investigated by means of Computational Fluid Dynamics (CFD) to evaluate the pressure loss under different pressure conditions, simulating different vessel resistances, on the pulmonary arteries. A total flow of 3 L/min, with a distribution between the inferior vena cava (IVC) and the superior vena cava (SVC) equal to 6/4, was investigated; three different boundary conditions for the pressure were imposed, resulting in three simulations in steady-state conditions, to the right pulmonary artery (RPA) and to the left pulmonary artery (LPA), simulating a balanced (ΔP_LPA-RPA=0 mmHg) and two unbalanced pulmonary resistances to blood flow (a pressure difference ΔP_LPA-RPA = ±2 mmHg, respectively). The geometry for the TECPC was realized according to MRI derived physiological values for the vessels and for the configuration adopted for the anastomosis (the extra-cardiac conduit was inclined 22° towards the left pulmonary artery with respect to the IVC axis). The computed power losses agree with previous in vitro Particle Image Velocimetry investigations. The results show that a higher resistance on the LPA causes the greater pressure loss for the TECPC under study, while the minimum pressure loss can be achieved balancing the pulmonary resistances, subsequently obtaining a balanced flow repartition towards the lungs.