Journal of biomechanics
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Journal of biomechanics · Jan 2013
Case ReportsPredictive modeling of the virtual Hemi-Fontan operation for second stage single ventricle palliation: two patient-specific cases.
Single ventricle hearts are congenital cardiovascular defects in which the heart has only one functional pumping chamber. The treatment for these conditions typically requires a three-staged operative process where Stage 1 is typically achieved by a shunt between the systemic and pulmonary arteries, and Stage 2 by connecting the superior venous return to the pulmonary circulation. Surgically, the Stage 2 circulation can be achieved through a procedure called the Hemi-Fontan, which reconstructs the right atrium and pulmonary artery to allow for an enlarged confluence with the superior vena cava. ⋯ In contrast, varying HR, PVR, and SVR led to significant changes in theses clinically relevant global parameters. Adopting a work-flow of customized virtual planning of the Hemi-Fontan procedure with patient-specific data, this study demonstrates the ability of multi-scale modeling to reproduce patient specific flow conditions under differing physiological states. Results demonstrate that the same operation performed in two different patients can lead to different hemodynamic characteristics, and that modeling can be used to uncover physiologic changes associated with different clinical conditions.
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Journal of biomechanics · Jan 2013
ReviewThe Syncardia(™) total artificial heart: in vivo, in vitro, and computational modeling studies.
The SynCardia(™) total artificial heart (TAH) is the only FDA-approved TAH in the world. The SynCardia(™) TAH is a pneumatically driven, pulsatile system capable of flows of >9L/min. The TAH is indicated for use as a bridge to transplantation (BTT) in patients at imminent risk of death from non-reversible bi-ventricular failure. ⋯ To aid in the development of a new "pediatric," TAH an engineering methodology known as "Device Thrombogenicity Emulation (DTE)", that we have recently developed and described, is being employed. Recently, to further our engineering understanding of the TAH, as steps towards next generation designs we have: (1) assessed of the degree of platelet reactivity induced by the present clinical 70 cc TAH using a closed loop platelet activity state assay, (2) modeled the motion of the TAH pulsatile mobile diaphragm, and (3) performed fluid-structure interactions and assessment of the flow behavior through inflow and outflow regions of the TAH fitted with modern bi-leaflet heart valves. Developing a range of TAH devices will afford biventricular replacement therapy to a wide range of patients, for both short and long-term therapy.
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Journal of biomechanics · Jan 2013
Numerical investigation of a novel aortic cannula aimed at reducing cerebral embolism during cardiovascular bypass surgery.
The generation of emboli during cardiopulmonary bypass (CPB) is profoundly affected by the hemodynamic properties of the aortic cannula used in the current study. The aim of the current work was to numerically investigate the hemodynamic efficiency and feasibility of a novel, backward suction cannula (BSC), designed to drastically reduce the potential risk for cerebral emboli (CEP). In line with the standard cannulae, the BSC provides oxygenated blood from the CPB machine through its primary lumen. ⋯ Differences between the investigated cannulae in terms of these measures were tested using analyses of variance tests (ANOVAs). Results indicate that the BSC exhibited a significant improvement of the cannula performance in terms of CEP with no significant change in the risk for other hemodynamic complications, such as hemolysis or atheroembolism (AP and IH). These findings suggest the advantageous use of the BSC in the clinical setting for its potential to diminish the risk for cerebral emboli, which presents the most pertinent cause of noncardiac complications following open heart surgery.
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Journal of biomechanics · Jan 2013
Spring-like gait mechanics observed during walking in both young and older adults.
A spring loaded inverted pendulum model successfully demonstrated the oscillatory behavior of the center of mass (CoM) and corresponding ground reaction forces (GRFs) of young healthy subjects. This study questioned whether spring-like leg walking dynamics are consistently observed in the walking of older adults that exhibit different gait characteristics, such as slower gait speed, from the young. Eight young and eight older adult subjects participated in overground walking experiments performed at four different gait speeds, ranging from their self-selected speed to a maximum walking speed. ⋯ We observed that the GRFs data from both age groups were reasonably well fitted by spring-like leg dynamics throughout the broad range of gait speeds. The leg stiffness and damping constant consistently increased as a function of the walking speed in both age groups, but slightly greater variations of the model parameters were observed for the older adults' trials. The results imply that human walking dynamics and the variation with respect to age can be well captured by spring-like leg dynamics.