Modeling of the Norwood circulation: effects of shunt size, vascular resistances, and heart rate

Abstract

Hypoplastic left heart syndrome is the most common lethal cardiac malformation of the newborn. Its treatment, apart from heart transplantation, is the Norwood operation. The initial procedure for this staged repair consists of reconstructing a circulation where a single outlet from the heart provides systemic perfusion and an interpositioning shunt contributes blood flow to the lungs. To better understand this unique physiology, a computational model of the Norwood circulation was constructed on the basis of compartmental analysis. Influences of shunt diameter, systemic and pulmonary vascular resistance, and heart rate on the cardiovascular dynamics and oxygenation were studied. Simulations showed that 1) larger shunts diverted an increased proportion of cardiac output to the lungs, away from systemic perfusion, resulting in poorer O2 delivery, 2) systemic vascular resistance exerted more effect on hemodynamics than pulmonary vascular resistance, 3) systemic arterial oxygenation was minimally influenced by heart rate changes, 4) there was a better correlation between venous O2 saturation and O2 delivery than between arterial O2 saturation and O2 delivery, and 5) a pulmonary-to-systemic blood flow ratio of 1 resulted in optimal O2 delivery in all physiological states and shunt sizes.

A non-discrete method for computation of residence time in fluid mechanics simulations

“…The 0D domain consists of a lumped parameter network that models the heart and downstream circulation following our previous work ( Figure 7). [30][31][32] This multi-domain simulation, which models the vascular system in a closed loop, provides spatial and temporal information in the 3D domain and global temporal information at particular points in the 0D domain. A robust iterative implicit method is used to couple the 3D and 0D domain through the boundaries.…”

Simulation of Aorta Artery Aneurysms Using Active Electronic Circuit

“…In the next part, the compliance of aorta in both healthy and abnormal conditions is determined. The compliance of a elastic vessel with certain diameter and length is calculated [2] according to Equation (2): C=(3П.r 3 .Z)/2Eh (2) In this Equation, (r) is radius of the vessel, (Z) length, (E) elastic module and (h) is the thickness of the vessel. The Compliance of aorta in healthy condition can be calculated by Equation (2).…”

“…Most of aorta aneurysms are fusiform (concentric radial dilatation) but infrequently may be saccular (concentric radial dilatation). The method of modeling the cardiovascular system has previously been applied to the study of system pathologies by a number of authors [1][2][3][4][5] . These studies can be grouped loosely into two approaches: highly idealized models which are concerned with a simple cardiovascular system and very complex models which have attempted to predict the detailed behavior of cardiovascular system and one special pathology.…”

Computational Models of Aortic Coarctation in Hypoplastic Left Heart Syndrome: Considerations on Validation of a Detailed 3D model

“…Such models can provide output data that can be difficult to acquire in vivo because the data can be challenging to measure (e.g., coronary blood flow) or restricted by patient conditions (e.g., immediately post-operative). Compared to in vivo analyses, both experimental and computational modeling methodologies have the advantage of creating reproducible and controllable environments in which data can be systematically acquired and parametric studies performed (1)(2)(3). In vitro models are valuable for device fatigue testing (4), and as teaching and practice tools (5), allowing for device implantation and physical manipulations, naturally taking into account fluid-structure interaction phenomena.…”