Numerical investigation of the haemodynamics in the human fetal umbilical vein/ductus venosus based on the experimental data

Effect of Extra-abdominal Vein Varix on the Stress Distribution in Umbilical Cord: A Simulation Study

The umbilical cord is a critical structure linking the fetus to the placenta and is surrounded by the amniotic fluid. It is composed of a vein, two arteries coiled around the vein, and Wharton's jelly surrounding the blood vessels. In this study, the stress distribution of the arteries, vein, and Wharton's jelly of an umbilical cord with extra-abdominal umbilical vein varix is analyzed for varying amniotic pressure using finite element analysis. Four diameters are considered for the umbilical vein, 6.5 mm, 11 mm, 15.5 mm, and 20 mm, with 6.5 mm corresponding to the normal vein diameter. The amniotic pressure is varied from 15-105 mmHg in steps of 15 mmHg, to simulate contractions during labour. Stress distribution is obtained and the peak stresses are analyzed. According to the results, the peak stress in the Wharton's jelly and the umbilical vein increases nonlinearly with increasing amniotic pressure. The peak stress in umbilical arteries initially decreases till the amniotic pressure reaches 45 mmHg and thereafter increases. This might be due to asymmetric deformation of the Wharton's jelly at the pressure range below arterial pressure.Clinical Relevance- This study could be useful in understanding the fundamental mechanics of extra-abdominal umbilical vein varix and help in development of better treatment protocols.

Mending a broken heart: In vitro, in vivo and in silico models of congenital heart disease

Birth defects contribute to ∼0.3% of global infant mortality in the first month of life, and congenital heart disease (CHD) is the most common birth defect among newborns worldwide. Despite the significant impact on human health, most treatments available for this heterogenous group of disorders are palliative at best. For this reason, the complex process of cardiogenesis, governed by multiple interlinked and dose-dependent pathways, is well investigated. Tissue, animal and, more recently, computerized models of the developing heart have facilitated important discoveries that are helping us to understand the genetic, epigenetic and mechanobiological contributors to CHD aetiology. In this Review, we discuss the strengths and limitations of different models of normal and abnormal cardiogenesis, ranging from single-cell systems and 3D cardiac organoids, to small and large animals and organ-level computational models. These investigative tools have revealed a diversity of pathogenic mechanisms that contribute to CHD, including genetic pathways, epigenetic regulators and shear wall stresses, paving the way for new strategies for screening and non-surgical treatment of CHD. As we discuss in this Review, one of the most-valuable advances in recent years has been the creation of highly personalized platforms with which to study individual diseases in clinically relevant settings.

The biomechanics of the umbilical cord Wharton Jelly: Roles in hemodynamic proficiency and resistance to compression

The umbilical cord is a complex structure containing three vessels, one straight vein and two coiled arteries, encased by the Wharton Jelly (WJ) a spongy structure made of collagen and hydrated macromolecules. Fetal blood reaches the placenta through the arteries and flows back to the fetus through the vein. The role of the WJ in maintaining cord circulation proficiency and the ultimate reason for arterial coiling still lack of reasonable mechanistic interpretations. We performed biaxial tension tests and evidenced significant differences in the mechanical properties of the core and peripheral WJ. The core region, located between the arteries and the vein, resulted rather stiffer close to the fetus. Finite element modelling and optimization based inverse method were used to create 2D and 3D models of the cord and to simulate stress distribution in different hemodynamic conditions, compressive loads and arterial coiling. We recorded a facilitated stress transmission from the arteries to the vein through the soft core of periplacental WJ. This condition generates a pressure gradient that boosts the venous backflow circulation towards the fetus. Peripheral WJ allows arteries to act as pressure buffering chambers during the cardiac diastole and helps to dissipate compressive forces away from vessels. Altered WJ biomechanics may represent the structural basis of cord vulnerability in many high-risk clinical conditions.