A two dimensional finite analytic method to simulate flow patterns due to wall motion abnormality during left ventricular ejection

A two-dimensional finite analytic technique is used to simulate left ventricular (LV) wall motion abnormality during systole. The numerical technique solves 2-D Navier-Stokes equations for viscous, incompressible, unsteady flow. The velocity profile within the chamber is obtained as the time-dependent wall motion is used as input. The areas of akinesis and diskinesis show backflow and low-velocity gradient at the wall. This may have implication in the formation of LV clot. A fluid-mechanical model may serve as an adjunct to the high-resolution imaging modalities capable of flow visualization of the contrast material

A simulation of three-dimensional systolic flow dynamics in a spherical ventricle: Effects of abnormal wall motion

Alterations in left ventricle (LV) wall motion induced by ischemia will affect flow dynamics, and these altered flow fields can be used to evaluate LV pumping efficiency. LV chamber flow fields were obtained in this study by solving the discretized three-dimensional Navier-Stokes equations for viscous, incompressible unsteady flow by using the finite analytic method. Several cases of abnormal wall motion (AWM) were simulated by a manipulation of the boundary conditions to produce regions of hypokinesis, akinesis, and dyskinesis. These solutions were used to determine the central ejection region (CER), defined as the region of flow domain in which the obtained velocity field vectors are aligned ±3° from the LV long axis. A CER coefficient was computed from information on the location and orientation of the CER within the LV cavity. Contraction of the spherical ventricle produced a vector field that was symmetric with respect to the long axis. For the simulations of AWM, an asymmetrical flow pattern developed, became more pronounced with increasing severity of AWM, and resulted in a shorter CER that shifted toward the ischemic region. The CER coefficients decreased monotonically with increased severity in AWM from 0.948 in the normal case to a low of 0.164 for the most severe case of AWM. The CER coefficient quantitatively displayed the sensitivity of the flow patterns to even moderate degrees of hypokinesis. In addition, visualization of the three-dimensional flow field reinforced the necessity of three-dimensional simulations to capture aspects of the flow that existing methods of two-dimensional flow imaging that use ultrasound may miss. © 1995 Biomedical Engieering Society

A New Program in Leadership Engineering

The University of Texas at El Paso (UTEP) is planning to pioneer and establish a new undergraduate program in Leadership Engineering. The overarching program goal is graduation of a new pedigree of qualified engineers with the soft skills , business acumen and strategic foresight, in addition to engineering prowess, to meet the needs of industry in the 21st century. Following the recommendation from James Duderstadt\u27s Engineering for a Changing World [1], we propose a new paradigm for the education of the engineering leaders of the 21 century. The Duderstadt model mirrors the medical school training model that is credited with propelling advancement in medical practice during the last century, where the BS degree includes a broad-based curriculum of engineering design, project management, technology, ingenuity and innovation, along with business, communication, ethics, and social sciences. This foundation is then followed by post-graduate study, via a professional Master\u27s degree program, in a specific discipline or concentration. The Leadership Engineering degree program is a first important, and viable, step towards that new paradigm. A large fraction of the graduates of the Leadership Engineering program are anticipated to pursue professional graduate degrees in a variety of engineering fields. Through a curriculum that provides a framework for building successful businesses, students graduating from the program may also move into the booming technology services sector or choose to start their own innovative companies. Finally, graduates of the Leadership Engineering program will be prepared to serve as leadership engineering educators in the K-12 sector, or for further graduate preparation in the expanding field of engineering education. s

A new program in leadership engineering

The University of Texas at El Paso (UTEP) is planning to pioneer and establish a new undergraduate program in Leadership Engineering. The overarching program goal is graduation of a new pedigree of qualified engineers with the soft skills , business acumen and strategic foresight, in addition to engineering prowess, to meet the needs of industry in the 21st century. Following the recommendation from James Duderstadt\u27s Engineering for a Changing World [1], we propose a new paradigm for the education of the engineering leaders of the 21 century. The Duderstadt model mirrors the medical school training model that is credited with propelling advancement in medical practice during the last century, where the BS degree includes a broad-based curriculum of engineering design, project management, technology, ingenuity and innovation, along with business, communication, ethics, and social sciences. This foundation is then followed by post-graduate study, via a professional Master\u27s degree program, in a specific discipline or concentration. The Leadership Engineering degree program is a first important, and viable, step towards that new paradigm. A large fraction of the graduates of the Leadership Engineering program are anticipated to pursue professional graduate degrees in a variety of engineering fields. Through a curriculum that provides a framework for building successful businesses, students graduating from the program may also move into the booming technology services sector or choose to start their own innovative companies. Finally, graduates of the Leadership Engineering program will be prepared to serve as leadership engineering educators in the K-12 sector, or for further graduate preparation in the expanding field of engineering education. s

Validation of a 3-D numerical model of LV ejection

The single most common cause of death in western culture is ischemic heart disease, which results from insufficient coronary artery blood flow. A numerical left ventricular model was developed to detect the abnormal wall motion by analyzing the velocity field inside of the left ventricle. The aim of this study is to validate the numerical model by comparing its results with the experiment results. There was good qualitative agreement between the experimental and numerical results

Simulation of turbulent pulsatile flow past a mechanical heart valve

The thrombogenicity of all mechanical heart valves is primarily due to an activation of platelets. As a blood platelet passes through a mechanical heart valve it is exposed to varying degrees of shear, elongational and turbulent stresses. Numerical simulation of turbulent pulsatile flow through a 2D model of a St. Jude bileaflet valve in the aortic position was obtained, to allow the quantitative examination of the cumulative effects of elevated stresses on the blood platelets. The simulation was used to indicate the potential for stress-induced platelet activation due to anomalous flow patterns produced by the valve, a problem shared by all mechanical heart valves designs in use today

Velocity and turbulence measurements past mitrial valve prostheses in a model left ventricle

Thrombogenesis and hemolysis have both been linked to the flow dynamics past heart valve prostheses. To learn more about the particular flow dynamics past mitral valve prostheses in the left ventricle under controlled experimental conditions, an in vitro study was performed. The experimental methods included velocity and turbulent shear stress measurements past caged-ball, tilting disc, bileaflet, and polyurethane trileaflet mitral valves in an acrylic rigid model of the left ventricle using laser Doppler anemometry. The results indicate that all four prosthetic heart valves studied create at least mildly disturbed flow fields. The effect of the left ventricular geometry on the flow development is to produce a stabilizing vortex which engulfs the entire left ventricular cavity, depending on the orientation of the valve. The measured turbulent shear stress magnitudes for all four valves did not exceed the reported value for hemolytic damage. However, the measured turbulent shear stresses were near or exceeded the critical shear stress reported in the literature for platelet lysis, a known precursor to thrombus formation. © 1991

Performance assessment of prosthetic heart valves using the energy index method

Traditional methods of characterizing valvular performance use some estimation of the effective opening area and the percent regurgitant volume. These methods are cumbersome because two parameters are used and their importance relative to one another is not revealed. The authors propose the use of a single parameter that is physically meaningful and accounts for characteristics of the valve throughout the cardiac cycle. The energy index, derived with use of a phase-by-phase analysis of the cardiac cycle, describes the energetic efficiency of the valve. The method\u27s final form is: EI = E ×(1-qq /qq )/E +E where E is the hydraulic energy available after systole, E is the energy dissipated in the valve while flow is positive, qq and qq are the regurgitant and forward volumes, respectively. Use of the EI requires on-line measurement of valvular flow rate and pressure drop. The El was applied to a Medtronic-Hall (Minneapolis, MN), 25 mm prosthetic valve mounted in the aortic position of a cardiovascular simulator. Mild and severe degrees of valvular stenosis and regurgitance were simulated. Results indicate that the EI is sensitive to either valvular condition and remains nearly constant, at 87%, for the normal valve tested over cardiac rates ranging 50 to 100 beats per minute. ps - + ps + ps + -