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Shang X.-K.,Wuhan Asia Heart Hospital | Zhang G.-C.,Wuhan Asia Heart Hospital | Zhong L.,National Heart Research Institute of Singapore | Zhong L.,National University of Singapore | And 3 more authors.
Experimental and Therapeutic Medicine | Year: 2016

The present study describes the case of a 2.5-year-old girl with double patent ductus arteriosus (PDA) that was successfully treated following interventional and surgical treatment. Bilateral ductus arteriosus is a very rare condition, which is assumed to occur when the branchial-type arterial system transforms into the mammalian-type arterial system during the development of the aorta and its branches. This case was misdiagnosed as ordinary PDA by echocardiography prior to the first surgery and the surgery was not successful because of poor accessibility. Enhanced computed tomography subsequently showed situs solitus, atrial situs, levocardia, right-sided aortic arch with right-sided descending aorta, an isolated left subclavian artery and double PDA. Interventional treatment was performed and intraoperative aortic arch angiography showed that the descending aorta was the origin of the first funnel-type PDA (PDA-1). The left subclavian artery was not connected to the aorta but was connected to the pulmonary artery with a very narrow winding duct, which was PDA-2. Interventional treatment via PDA-2 also failed because passing a guidewire through the twisted PDA-2 was difficult. The child was immediately transferred to the surgical operation room for double PDA ligation and left subclavian artery reconstruction under median thoracotomy. The surgical procedure succeeded and the patient recovered quickly. The failure of the interventional treatment may be attributed to the difficulty in establishing a path. The soft tip of the hardened guidewire was relatively long. If the hardened part of the wire was sent to the appropriate place to support the pathway, the soft tip would be forced to enter the vertebrobasilar artery system. A similar problem was encountered when the left subclavian artery was selected for intervention. Shortening the length of the soft tip of the hardened guidewire may have enabled smooth completion of the establishment of the pathway. However, this type of hardened guidewire requires specific production. © 2016, Spandidos Publications. All rights reserved. Source

Khalafvand S.S.,Nanyang Technological University | Hung T.-K.,University of Pittsburgh | Ng E.Y.-K.,Nanyang Technological University | Zhong L.,National Heart Research Institute of Singapore | Zhong L.,National University of Singapore
Computational and Mathematical Methods in Medicine | Year: 2015

Blood flow characteristics in the normal left ventricle are studied by using the magnetic resonance imaging, the Navier-Stokes equations, and the work-energy equation. Vortices produced during the mitral valve opening and closing are modeled in a two-dimensional analysis and correlated with temporal variations of the Reynolds number and pressure drop. Low shear stress and net pressures on the mitral valve are obtained for flow acceleration and deceleration. Bernoulli energy flux delivered to blood from ventricular dilation is practically balanced by the energy influx and the rate change of kinetic energy in the ventricle. The rates of work done by shear and energy dissipation are small. The dynamic and energy characteristics of the 2D results are comparable to those of a 3D model. © 2015 Seyed Saeid Khalafvand et al. Source

Doost S.N.,Swinburne University of Technology | Zhong L.,National University of Singapore | Zhong L.,National Heart Research Institute of Singapore | Su B.,National Heart Research Institute of Singapore | Morsi Y.S.,Swinburne University of Technology
Computer Methods and Programs in Biomedicine | Year: 2016

Recently, various non-invasive tools such as the magnetic resonance image (MRI), ultrasound imaging (USI), computed tomography (CT), and the computational fluid dynamics (CFD) have been widely utilized to enhance our current understanding of the physiological parameters that affect the initiation and the progression of the cardiovascular diseases (CVDs) associated with heart failure (HF). In particular, the hemodynamics of left ventricle (LV) has attracted the attention of the researchers due to its significant role in the heart functionality. In this study, CFD owing its capability of predicting detailed flow field was adopted to model the blood flow in images-based patient-specific LV over cardiac cycle. In most published studies, the blood is modeled as Newtonian that is not entirely accurate as the blood viscosity varies with the shear rate in non-linear manner. In this paper, we studied the effect of Newtonian assumption on the degree of accuracy of intraventricular hemodynamics. In doing so, various non-Newtonian models and Newtonian model are used in the analysis of the intraventricular flow and the viscosity of the blood. Initially, we used the cardiac MRI images to reconstruct the time-resolved geometry of the patient-specific LV. After the unstructured mesh generation, the simulations were conducted in the CFD commercial solver FLUENT to analyze the intraventricular hemodynamic parameters. The findings indicate that the Newtonian assumption cannot adequately simulate the flow dynamic within the LV over the cardiac cycle, which can be attributed to the pulsatile and recirculation nature of the flow and the low blood shear rate. © 2016 Elsevier Ireland Ltd. Source

Tan G.X.Y.,National University of Singapore | Jamil M.,National University of Singapore | Tee N.G.Z.,National Heart Research Institute of Singapore | Zhong L.,National Heart Research Institute of Singapore | And 2 more authors.
Annals of Biomedical Engineering | Year: 2015

Recent animal studies have provided evidence that prenatal blood flow fluid mechanics may play a role in the pathogenesis of congenital cardiovascular malformations. To further these researches, it is important to have an imaging technique for small animal embryos with sufficient resolution to support computational fluid dynamics studies, and that is also non-invasive and non-destructive to allow for subject-specific, longitudinal studies. In the current study, we developed such a technique, based on ultrasound biomicroscopy scans on chick embryos. Our technique included a motion cancelation algorithm to negate embryonic body motion, a temporal averaging algorithm to differentiate blood spaces from tissue spaces, and 3D reconstruction of blood volumes in the embryo. The accuracy of the reconstructed models was validated with direct stereoscopic measurements. A computational fluid dynamics simulation was performed to model fluid flow in the generated construct of a Hamburger–Hamilton (HH) stage 27 embryo. Simulation results showed that there were divergent streamlines and a low shear region at the carotid duct, which may be linked to the carotid duct’s eventual regression and disappearance by HH stage 34. We show that our technique has sufficient resolution to produce accurate geometries for computational fluid dynamics simulations to quantify embryonic cardiovascular fluid mechanics. © 2015 Biomedical Engineering Society Source

Su B.,National Heart Research Institute of Singapore | Kabinejadian F.,National University of Singapore | Phang H.Q.,National University of Singapore | Kumar G.P.,Institute of High Performance Computing of Singapore | And 8 more authors.
PLoS ONE | Year: 2015

This work presents a numerical simulation of intraventricular flow after the implantation of a bileaflet mechanical heart valve at the mitral position. The left ventricle was simplified conceptually as a truncated prolate spheroid and its motion was prescribed based on that of a healthy subject. The rigid leaflet rotation was driven by the transmitral flow and hence the leaflet dynamics were solved using fluid-structure interaction approach. The simulation results showed that the bileaflet mechanical heart valve at the mitral position behaved similarly to that at the aortic position. Sudden area expansion near the aortic root initiated a clockwise anterior vortex, and the continuous injection of flow through the orifice resulted in further growth of the anterior vortex during diastole, which dominated the intraventricular flow. This flow feature is beneficial to preserving the flow momentum and redirecting the blood flow towards the aortic valve. To the best of our knowledge, this is the first attempt to numerically model intraventricular flow with the mechanical heart valve incorporated at the mitral position using a fluid-structure interaction approach. This study facilitates future patient-specific studies. © 2015 Su et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Source

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