Effect of Outflow Tract Banding on Embryonic Cardiac Hemodynamics.

Venkat Chivukula,Sandra Rugonyi,Aiping Liu,Sevan Goenezen

doi:10.3390/jcdd3010001

Abstract

We analyzed heart wall motion and blood flow dynamics in chicken embryos using in vivo optical coherence tomography (OCT) imaging and computational fluid dynamics (CFD) embryo-specific modeling. We focused on the heart outflow tract (OFT) region of day 3 embryos, and compared normal (control) conditions to conditions after performing an OFT banding intervention, which alters hemodynamics in the embryonic heart and vasculature. We found that hemodynamics and cardiac wall motion in the OFT are affected by banding in ways that might not be intuitive a priori. In addition to the expected increase in ventricular blood pressure, and increase blood flow velocity and, thus, wall shear stress (WSS) at the band site, the characteristic peristaltic-like motion of the OFT was altered, further affecting flow and WSS. Myocardial contractility, however, was affected only close to the band site due to the physical restriction on wall motion imposed by the band. WSS were heterogeneously distributed in both normal and banded OFTs. Our results show how banding affects cardiac mechanics and can lead, in the future, to a better understanding of mechanisms by which altered blood flow conditions affect cardiac development leading to congenital heart disease.

Highlights

During embryonic development, the heart transforms from a linear tube to a four-chambered heart
We further focus on the heart outflow tract (OFT), the distal portion of the heart that connects it to the circulation, and that later gives rise to a portion of the interventricular septum, the semilunar valves, and the pulmonary and aortic trunks
We have developed strategies to reconstruct 4D images (3D + time) of the beating heart using optical coherence tomography (OCT) [22], and to segment the heart layers over time [23], enabling analysis of heart motion under normal and altered hemodynamic conditions

Summary

Introduction

The heart transforms from a linear tube to a four-chambered heart. CFD modeling was used to complement imaging data in capturing the details of blood flow within the OFT, and in facilitating computation of wall shear stresses, a recognized stimulant of mechanotransduction leading to tissue remodeling [2,25,26,27,28] Using these techniques, we analyzed blood flow and cardiac motion of the day 3 embryonic chick heart OFT under normal conditions and after altering hemodynamics by outflow tract banding, an intervention in which a suture restricts OFT cardiac motion affecting hemodynamics. We found differences among control and banded embryos in blood flow conditions and on the dynamics of the OFT beating tissues These cardiac mechanical changes contribute to the formation of heart defects and are intrinsically linked to congenital heart disease

Methods

Embryo Preparation and Hemodynamic Intervention

OCT Imaging

Cross-Sectional Analysis

Blood Flow within the OFT

Conclusions