Blood Flow Dynamics at the Pulmonary Artery Bifurcation

Abstract

Knowledge of physiologic hemodynamics is a fundamental requirement to establish pathological findings. However, little is known about the normal flow fields in the pulmonary arteries, especially for children. The purpose of this study is to characterize flow patterns in the pulmonary artery bifurcation of healthy pediatric subjects using direct numerical simulations. A realistic geometry is obtained via statistical shape modeling, by averaging five subject-specific digital models extracted from cardiovascular magnetic resonance datasets of healthy volunteers. Boundary conditions are assigned to mimic physiological conditions at rest, corresponding to a peak Reynolds number equal to 3400 and a Womersley number equal to 15. Results show that the normal bifurcation is highly hemodynamically efficient, as measured by an energy dissipation index. The curvature of the pulmonary arteries is sufficiently small to prevent flow separation along the inner walls, and no signs of a turbulent-like state are found. In line with previous imaging studies, a helical structure protruding into the right pulmonary artery is detected, and its formation mechanism is elucidated in the paper. These findings might help to identify abnormal flow features in patients with altered anatomic and physiologic states, particularly those with repaired congenital heart disease.

Characterization of Flow Dynamics in the Pulmonary Bifurcation of Patients With Repaired Tetralogy of Fallot: A Computational Approach

“…This study demonstrates that the anatomy of the pulmonary arteries of repaired tetralogy of Fallot patients varies greatly within the population. A characteristic difference from healthy subjects is that the left pulmonary artery is highly curved ( 11 ). The scope of this study was to evaluate the effect of morphological characteristics on the flow development in models of rTOF patients.…”

“…where ν is the kinematic viscosity and R is the radius of curvature (1/curvature). Re max was calculated using the local velocity at each branch, while to calculate the Dean number in the RPA and LPA branches, Re max , as calculated for the MPA branch, was multiplied by the percentage of flow split in Equation ( 7 ), as suggested by another study in the literature ( 11 ). The Reynolds number, Re , is used to characterize whether the fluid presents a laminar or turbulent flow behavior, based on the ratio of inertial to viscous forces, while the Womersley, Wo , and Dean numbers are dimensionless parameters utilized to characterize flow pulsatility in relation to viscous flows and flows in curved pipes, respectively.…”

Hemodynamics in the Aorta and Pulmonary Arteries of Congenital Heart Disease Patients: A Mini Review

“…The pulmonary junction is found hemodynamically efficient in healthy subjects 30 , with a 10% decrease in energy efficiency under exercise conditions 31 . In patients with TOF, decreasing the angle of the left pulmonary artery results in an increase of energy loss 32 . Flow recirculation occurs in the left pulmonary artery (LPA) branch in both healthy and TOF patients 7,30,32 , which is also the branch where regurgitation appears first in the repaired TOF population 33 .…”

“…In patients with TOF, decreasing the angle of the left pulmonary artery results in an increase of energy loss 32 . Flow recirculation occurs in the left pulmonary artery (LPA) branch in both healthy and TOF patients 7,30,32 , which is also the branch where regurgitation appears first in the repaired TOF population 33 . Branch stenosis, commonly observed in the LPA branch of TOF patients, can also alter the flow environment by displacing the point where flow impinges, a critical location in the wall shear stress distribution and differential branch pressure 7,32,34 , while also promoting an asymmetrical flow split in the two branches 35 .…”

“…Flow recirculation occurs in the left pulmonary artery (LPA) branch in both healthy and TOF patients 7,30,32 , which is also the branch where regurgitation appears first in the repaired TOF population 33 . Branch stenosis, commonly observed in the LPA branch of TOF patients, can also alter the flow environment by displacing the point where flow impinges, a critical location in the wall shear stress distribution and differential branch pressure 7,32,34 , while also promoting an asymmetrical flow split in the two branches 35 . In addition, vortices appear in stenotic regions of the pulmonary branches, compared to the helical flow which is visible in non-stenotic branches 35 .…”