Organ Dynamics and Hemodynamic of the Whole HH25 Avian Embryonic Heart, Revealed by Ultrasound Biomicroscopy, Boundary Tracking, and Flow Simulations

Sheldon Ho,Nhan Phan-Thien,Choon Hwai Yap,Wei Xuan Chan

doi:10.1038/s41598-019-54061-w

Sheldon Ho, Nhan Phan-Thien + Show 2 more

Open Access

https://doi.org/10.1038/s41598-019-54061-w

Copy DOI

Journal: Scientific Reports	Publication Date: Dec 1, 2019
Citations: 5	License type: open-access

Affiliation: National University of Singapore

Abstract

Congenital heart malformations occur to substantial number of pregnancies. Studies showed that abnormal flow biomechanical environments could lead to malformations, making it important to understand the biomechanical environment of the developing heart. We performed 4D high-frequency ultrasound scans of chick embryonic hearts at HH25 to study the biomechanics of the whole heart (atria and ventricle). A novel and high-fidelity motion estimation technique, based on temporal motion model and non-rigid image registration algorithm, allowed automatic tracking of fluid-structure boundaries from scan images, and supported flow simulations. Results demonstrated that atrial appendages were the most contractile portion of the atria, having disproportionately high contribution to atrial blood pumping for its volume in the atria. However, the atria played a small role in blood pumping compared to the ventricle, as it had much lower ejection energy expenditure, and as the ventricle appeared to be able to draw inflow from the veins directly during late diastole. Spatially and temporally averaged wall shear stresses (WSS) for various cardiac structures were 0.062–0.068 Pa, but spatial-averaged WSS could be as high as 0.54 Pa in the RV. WSS was especially elevated at the atrial inlet, atrioventricular junction, regions near to the outflow tract, and at dividing lines between the left and right atrium and left and right side of the ventricle, where septation had begun and the lumen had narrowed. Elevated WSS could serve as biomechanics stimulation for proper growth and development.

Highlights

We previously presented a technique to image the avian embryonic heart non-invasively in 4D using high-frequency ultrasound, and highlighted the subsequent image-processing necessary to distinguish between blood and tissue spaces[12,13]
We extended our imaging and simulations to the whole avian embryonic heart involving both the atria and the ventricle, to investigate atrial biomechanics, and the interplay between the two structures
Results demonstrated that the atria only had minor blood pumping energy contribution, and that the ventricle was capable of drawing blood directly from the veins

Summary

Introduction

We previously presented a technique to image the avian embryonic heart non-invasively in 4D using high-frequency ultrasound, and highlighted the subsequent image-processing necessary to distinguish between blood and tissue spaces[12,13] We applied this technique to support image-based computational fluid dynamics (CFD) flow simulations of the embryonic common ventricle[12] and aortic arches[13] to understand the embryonic cardiac biomechanics. To aid the biomechanics study, we implemented a novel automatic cardiac motion estimation algorithm, via prescribing a cyclic motion mathematical model to 3D pair-wise non-rigid image registration, and adopted careful optimization to ensure accurate cardiac boundary motion tracking. This approach enabled the reduction of errors and uncertainties associated with manual segmentation. The motion tracking algorithm enabled calculations of the surface deformational stretch

Methods

Findings

Discussion

Conclusion