Structure and motion design of a mock circulatory test rig.

Mock circulatory test rig (MCTR) is the essential and indispensable facility in the cardiovascular in vitro studies. The system configuration and the motion profile of the MCTR design directly influence the validity, precision, and accuracy of the experimental data collected. Previous studies gave the schematic but never describe the structure and motion design details of the MCTRs used, which makes comparison of the experimental data reported by different research groups plausible but not fully convincing.

Medical Applications for 3D Printing: Recent Developments.

This is a review of some of the recent developments in the application of 3D printing to medicine. The topic is introduced with a brief explanation as to how and why 3D is changing practice, teaching, and research in medicine. Then, taking recent examples of progress in the field, we illustrate the current state of the art.

Impeller-pump model derived from conservation laws applied to the simulation of the cardiovascular system coupled to heart-assist pumps.

Previous numerical models of impeller pumps for ventricular assist devices utilize curve-fitted polynomials to simulate experimentally-obtained pressure difference versus flow rate characteristics of the pumps, with pump rotational speed as a parameter. In this paper the numerical model for the pump pressure difference versus flow rate characteristics is obtained by analytic derivation. The mass, energy and angular momentum conservation laws are applied to the working fluid passing through the impeller geometry and coupled with the turbomachine's velocity diagram.

Optimization of Axial Pump Characteristic Dimensions and Induced Hemolysis for Mechanical Circulatory Support Devices.

The application of axial pumps as ventricular assist devices (VADs) requires significant modifications to the size and characteristics of industrial pumps due to the difference in flow fields of industrial and medical pumps. Industrial pumps operate in the region of Reynolds number Re = 10, whereas axial blood pumps operate in Re < 10. The common pump design technique is to rely on the performance of previously designed pumps using the concept of fluid dynamic similarity.

Computational Parametric Study of the Axial and Radial Clearances in a Centrifugal Rotary Blood Pump.

In centrifugal rotary blood pumps (RBP), clearances are a critical parameter in determining blood trauma. This study investigates the effect of axial clearance (Cax) and radial clearance (Crad) on the hydrodynamic and hemolytic performance of a centrifugal RBP. A centrifugal pump was parameterized so that it could be defined by geometric variables Cax and Crad.

The Effect of Geometry on the Efficiency and Hemolysis of Centrifugal Implantable Blood Pumps.

The application of centrifugal pumps as heart assist devices imposes design limitations on the impeller geometry. Geometry and operating parameters will affect the performance and the hemocompatibility of the device. Among all the parameters affecting the hemocompatibility, pressure, rotational speed, blade numbers, angle, and width have significant impact on the blood trauma.

The Effects of Ambulatory Accelerations on the Stability of a Magnetically Suspended Impeller for an Implantable Blood Pump.

This article describes the effects of ambulatory accelerations on the stability of a magnetically suspended impeller for use in implantable blood pumps. A magnetic suspension system is developed to control the radial position of a magnetic impeller using coils in the pump casing. The magnitude and periodicity of ambulatory accelerations at the torso are measured.

Optimization of Centrifugal Pump Characteristic Dimensions for Mechanical Circulatory Support Devices.

The application of artificial mechanical pumps as heart assist devices impose power and size limitations on the pumping mechanism, and therefore requires careful optimization of pump characteristics. Typically new pumps are designed by relying on the performance of other previously designed pumps of known performance using concepts of fluid dynamic similarity. Such data are readily available for industrial pumps, which operate in Reynolds numbers region of 10.

In-vitro investigation of cerebral-perfusion effects of a rotary blood pump installed in the descending aorta.

This study describes use of a cardiovascular simulator to replicate the hemodynamic responses of the cerebrovascular system with a mechanical circulatory support device operating in the descending aorta. To do so, a cerebral autoregulation unit was developed which replicates the dilation and constriction of the native cerebrovascular resistance system and thereby regulates the cerebral flow rate within defined limits. The efficacy of the replicated autoregulation mechanism was investigated by introducing a number of step alterations in mean aortic pressure and monitoring the cerebral flow.

Numerical and in vitro investigation of a novel mechanical circulatory support device installed in the descending aorta.

Traditional implantation techniques of assist devices from the apex of left ventricle to the ascending or descending aorta are highly invasive and carry substantial complications for end-stage heart failure patients. This study has shown that the descending aorta can be a promising location to install an implantable mechanical circulatory support with minimally invasive surgery. Herein, the hemodynamic effect of an in-house prototyped pump implanted in the descending aorta was investigated numerically as well as experimentally.

In vitro comparison of two different mechanical circulatory support devices installed in series and in parallel.

This study investigates the novel approach of placing a ventricular assist pump in the descending aorta in series configuration with the heart and compares it with the two traditional approaches of left-ventricle-to-ascending-aorta (LV-AA) and left-ventricle-to-descending-aorta (LV-DA) placement in parallel with the heart. Experiments were conducted by using the in-house simulator of the cardiovascular blood-flow loop (SCVL). The results indicate that the use of the LV-AA in-parallel configuration leads to a significant improvement in the systemic and pulmonic flow as the level of continuous flow is increased; however, this approach is considered highly invasive.

Oxidation and ignition of aluminum nanomaterials.

The oxidation and ignition of aluminum nanoparticles with a mean diameter of 150 nm are investigated with the help of simultaneous thermal analysis, X-ray powder diffraction, energy dispersive X-ray spectra analysis (EDS) and scanning and transmission electron microscopy at heating rates of 2-30 K min(-1). A unique early ignition reaction is observed when the heating rate is ≥8 K min(-1) and there is a co-existence of various polymorphs of alumina (γ-, δ-, θ-, and α-Al2O3) below the melting temperature of aluminum nanoparticles. It is proposed that such an early ignition reaction is due to a combined effect of solid phase transformation of the alumina shell and the early melting of the aluminum core, and is responsible for the co-existence of various polymorphs of alumina at the low temperature.

In vitro cardiovascular system emulator (bioreactor) for the simulation of normal and diseased conditions with and without mechanical circulatory support.

This article presents a new device designed to simulate in vitro flow rates, pressures, and other parameters representing normal and diseased conditions of the human cardiovascular system. Such devices are sometimes called bioreactors or "mock" simulator of cardiovascular loops (SCVLs) in literature. Most SCVLs simulate the systemic circulation only and have inherent limitations in studying the interaction of left and right sides of circulation.

Atherosclerotic plaques: is endothelial shear stress the only factor?

Initiation and development of atherosclerosis has largely been attributed to irregular shear stress patterns and values, in the current literature. Abnormalities such as low shear stress, reversing and oscillatory shear force patterns, as well as temporal variations of shear stress are the most cited factors. However, clinical findings have further indicated that plaques have still been formed and developed in arterial sites that possess relatively more steady and higher shear stresses than those observed in studies correlating low or oscillatory shear stresses with atherosclerosis.

Physiological control of an in-series connected pulsatile VAD: numerical simulation study.

This paper investigates ventricular assist device (VAD)-assisted cardiovascular dynamics under proportion-integration-differentiation (PID) feedback control. Previously, we have studied the cardiovascular responses under the support of an in-series connected reciprocating-valve VAD through numerical simulation, and no feedback control was applied in the VAD. In this research, we explore the contribution of the VAD control on the circulatory dynamics assisted by the reciprocating-valve VAD, in response to the changing physiological conditions.

Oxidation investigation of nickel nanoparticles.

This work reported an experimental investigation of complete oxidation of nickel nanoparticles using simultaneous thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC). Nickel nanoparticles and their elemental compositions were characterized by Brunauer-Emmett-Teller (BET) analysis, transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). The oxidation experiments were performed under isoconversion conditions for seven heating rates, varying from 2 to 20 K min(-1), with temperatures up to 1000 degrees C.

Numerical comparison of hemodynamics with atrium to aorta and ventricular apex to aorta VAD support.

We report the first attempt to study with numerical methods ventricular assist device (VAD) models and the effects of various inlet VAD cannulations, coupling physical explanations and numerical investigation conclusions with clinical research results. We compared the hemodynamic response with VAD support by using two distinct VAD-inlet cannulation configurations: left atrium to aorta and left ventricular apex to aorta. Impeller pump and displacement pump VADs are considered.

Numerical simulation of cardiovascular dynamics with different types of VAD assistance.

A variety of methods by which mechanical circulatory support (MCS) can be provided have been described. However, the haemodynamic benefits of the different methods have not been adequately quantified. The aim of this paper is to compare the haemodynamic effects of six forms of MCS by numerical simulation.

Numerical simulation of cardiovascular dynamics with left heart failure and in-series pulsatile ventricular assist device.

This article presents a numerical model for investigations of the human cardiovascular circulation system response, where the function of the impaired left ventricle is augmented by the pumping action of a pulsatile ventricular assist device (VAD) connected in series to the native heart. The numerical model includes a module for detailed heart valve dynamics, which helps to improve the accuracy of simulation in studying the pulsatile type VAD designs. Simulation results show that, for the case with left ventricular (LV) failure, the VAD support successfully compensates the impaired cardiovascular response, and greatly reduces the after-load of the diseased ventricle, thus assisting possible recovery of the ventricle from the diseased condition.

Effects of atrial contraction, atrioventricular interaction and heart valve dynamics on human cardiovascular system response.

Various simulation models of different complexity have been proposed to model the dynamic response of the human cardiovascular system. In a related paper we proposed an improved numerical model to study the dynamic response of the cardiovascular system, and the pressures, volumes and flow-rates in the four chambers of the heart, which included the effects of atrial contraction, atrioventricular interaction, and heart valve dynamics. This paper investigates the effects of each one of these aspects of the model on the overall dynamic system response.

A concentrated parameter model for the human cardiovascular system including heart valve dynamics and atrioventricular interaction.

Numerical modeling of the human cardiovascular system has always been an active research direction since the 19th century. In the past, various simulation models of different complexities were proposed for different research purposes. In this paper, an improved numerical model to study the dynamic function of the human circulation system is proposed.

Numerical simulation of cardiovascular dynamics with healthy and diseased heart valves.

This paper presents a new concentrated parameter model for cardiovascular dynamics that includes an innovative model of heart valve dynamics, which is embedded in the overall model of the four chambers of the heart and the systemic and pulmonary circulation loops. The heart chambers are described with a variable elastance model, and the systemic and pulmonary loops are described with modified Windkessel models. In modelling the heart valve dynamics, the various factors that influence the valve motion are examined, and the governing differential equation for valve motion is derived.