Pulse wave propagation along human aorta: a model study

Abstract

The problem of the pulse wave propagation and reflection along human aorta and the diagnostic importance of the pressure and flow signals are studied. The geometrical model is based on the detailed postmortem measurements on the systemic arterial trees. The aortic model consists of 36 aortic segments and 57 side branches of the aorta including the larger and medium vessels. It was shown most of the branches have zero wave reflection coefficients but the large branches like celiac, renal and iliac arteries could produce noticeable wave reflections. The smaller branches possess negative wave reflection coefficient and, thus, contribute to the blood suction effect and lower aortic resistance to the blood flow. Mathematical model is based on the axisymmetric incompressible Navier-Stokes equations for blood and the momentum equations for incompressible viscoelastic arterial wall. The Windkessel and structured tree outflow boundary conditions at the outlets of the branches have been used. The solution has been found as superposition of the forward and backward running waves. The blood flow curves measured in vivo by Doppler ultrasound in the larger systemic arteries of healthy volunteers have been used for identification of the model parameters. It is shown, the individual geometry plays an essential role in the location of the positive and negative wave reflection sites along the aorta and, thus, in the pressure and flow patterns and blood distribution into the branches. The influence of occlusion of the iliac arteries, low/high wall rigidity, and total length of aorta are studied on different individual geometries. The model can be used for determination of the individual parameters for patient-specific cardiovascular models and further modeling of the outcomes of the surgical and therapeutic procedures.