Simulation of Pulsatile Blood Flow With a Wall Step Transition

2008 ◽  
Author(s):  
Scott C. Corbett ◽  
Ahmet U. Coskun ◽  
Hamid N-Hashemi
Keyword(s):  
Heart Valves ◽  
Cost Effective ◽  
Implantable Devices ◽  
Ventricular Assist Devices ◽  
Prosthetic Heart Valves ◽  
Pulsatile Blood Flow ◽  
Ventricular Assist ◽  
Effective Manner ◽  
Flowing Blood ◽  
Step Transition

Implantable devices in direct contact with flowing blood, for example, coronary stents, continuous flow and pulsatile flow ventricular assist devices, prosthetic heart valves, catheters and cannulae are currently being used to treat many medical conditions. However, thromboembolism and the attendant risk for ischemic stroke remains an impediment for all these devices. A prudent approach to developing these devices in a cost effective manner should include optimization for thrombogenic performance before going into expensive preclinical and clinical trials.

Evaluation of Platelet Activation Models With Dynamic Shear Stress In Vitro Experiments

2012 ◽  
Author(s):  
Jawaad Sheriff ◽  
Michalis Xenos ◽  
João S. Soares ◽  
Jolyon Jesty ◽  
Danny Bluestein
Keyword(s):  
Platelet Activation ◽  
Heart Valves ◽  
Ventricular Assist Devices ◽  
Prosthetic Heart Valves ◽  
Shear Stresses ◽  
Ventricular Assist ◽  
Relative Paucity ◽  
Valvular Diseases ◽  
End Stage

Blood recirculating devices, which include ventricular assist devices and prosthetic heart valves, are necessary for some patients suffering from end-stage heart failure and valvular diseases. However, disturbed flow patterns in these devices cause shear-induced platelet activation and aggregation. Thromboembolic complications resulting from this platelet behavior necessitates lifelong anticoagulant therapy for patients implanted with such devices. In addition, blood recirculating device manufacturers mostly test and optimize their products for hemolysis, which occurs at shear stresses ten-fold higher than required for platelet activation. The relative paucity of optimization for flow-induced thrombogenicity is further exacerbated by the fact that there are few predictive shear-induced platelet activation models.

The cytochemical demonstration of bacteria in total artificial heart implant specimens

1987 ◽  
Vol 45 ◽  
pp. 778-779 ◽  
Author(s):  
J. Hanker ◽  
B. Giammara ◽  
J. Dobbins ◽  
W. DeVries
Keyword(s):  
Defense Mechanisms ◽  
Artificial Heart ◽  
Heart Valves ◽  
Opportunistic Pathogen ◽  
Total Artificial Heart ◽  
Ventricular Assist Devices ◽  
Prosthetic Heart Valves ◽  
Ventricular Assist ◽  
Cytochemical Demonstration ◽  
Biomaterial Surfaces

Implantation of the total artificial heart and its associated systems, such as the pneumatic driving system, or other cardiovascular prostheses such as ventricular assist devices, intravenous catheters, ventriculo-atrial shunts, pacemaker electrodes and prosthetic heart valves can be complicated by the problem of bacterial infection. Staphylococcus epidermidis. a ubiquitous commensal of human skin and mucous membranes normally does not cause disease in man. It is now recognized, however, as an opportunistic pathogen of biomaterial implants especially cardiovascular protheses. This is due to its ability to undergo transformation to produce mucoid or polysaccharide extracellular coating substances which promote its adherence to biomaterial surfaces and protect the bacteria against antibiotics and host defense mechanisms; this results in increased virulence of the slime-producing strains.

Design Optimization of a Novel Polymeric Prosthetic Heart Valve and a Ventricular Assist Device via Device Thrombogenicity Emulation

2013 ◽  
Author(s):  
Thomas E. Claiborne ◽  
Wei-Che Chiu ◽  
Marvin J. Slepian ◽  
Danny Bluestein
Keyword(s):  
Heart Valves ◽  
Anticoagulation Therapy ◽  
Prosthetic Heart Valve ◽  
Total Artificial Heart ◽  
Ventricular Assist Devices ◽  
Circulatory Support ◽  
Prosthetic Heart Valves ◽  
Ventricular Assist ◽  
Mechanical Circulatory Support Devices ◽  
Optimization Methodology

Thrombotic complications, such as hemorrhage or embolism, remain a major concern of blood contacting medical devices [1], including prosthetic heart valves (PHV) and mechanical circulatory support devices, e.g. ventricular assist devices (VAD) or the Total Artificial Heart (TAH) [2]. In most cases device recipients require life-long anticoagulation therapy, which increases the risk of hemorrhagic stroke and other bleeding disorders. In order to obviate the need for anticoagulants and reduce stroke risks, our group developed a unique optimization methodology, Device Thrombogenicity Emulation (DTE) [2–5]. With the DTE, the thrombogenic potential of a device is evaluated using extensive numerical modeling and calculating multiple platelet trajectories flowing through the device. The platelet stress-time waveforms are then emulated in our Hemodynamic Shearing Device (HSD) and their activation level is measured with our Platelet Activation State (PAS) assay. This provides a proxy validation of the simulation. We identify high shear stress producing regions within the device and modify its design to reduce or eliminate those potentially thrombogenic ‘hot-spots.’ Through an iterative process, we can optimize the device design prior to prototyping.

Demonstration of the Bacterial-Biomaterial Interface in Implant Specimens

1987 ◽  
Vol 110 ◽  
Author(s):  
J. J. Dobbins ◽  
B. L. Giammara ◽  
J. S. Hanker ◽  
P. E. Yates ◽  
W. C. DeVries
Keyword(s):  
Defense Mechanisms ◽  
Heart Valves ◽  
Opportunistic Pathogen ◽  
Total Artificial Heart ◽  
Ventricular Assist Devices ◽  
Prosthetic Heart Valves ◽  
Electron Microscopic ◽  
Ventricular Assist ◽  
Biomaterial Surfaces ◽  
Pacemaker Electrodes

AbstractBacterial infection can be a problem associated with biomaterial implants especially with the total artificial heart or other cardiovascular prostheses such as ventricular assist devices, intravenous catheters, ventriculo-atrial shunts, pacemaker electrodes and, rarely, prosthetic heart valves. Bacterial commensals such as Staphylococcus epidermidis, which is ordinarily non-infective in human skin and mucous membranes, is now recognized as an opportunistic pathogen of biomaterial implants, particularly cardiovascular prostheses. In these implantations the S. epidermidis undergoes transformation to produce mucoid or polysaccharide extracellular coating substances. The latter promote bacterial adherence to biomaterial surfaces and protect the bacteria to some extent against antibiotics and host defense mechanisms. The result is increased virulence of the slime-producing strains. A number of techniques have been developed in our laboratories which facilitate identification of such bacterial pathogens on biopsy or postmortem specimens. These light and analytical electron microscopic methodologies include special cytochemical staining and rapid drying and embedding methods. Their efficacy and accuracy have been verified by studies on cultured and subcultured pathogens which are more time consuming. It is of interest that the microscopic methods showed the presence of macrophages as well as neutrophils on the specimens.

Pathological findings in explanted prosthetic heart valves from ventricular assist devices

Pathology ◽  
2008 ◽  
Vol 40 (4) ◽  
pp. 377-384 ◽  
Author(s):  
Nasir A. Khan ◽  
Jagdish Butany ◽  
Taylor Zhou ◽  
Heather J. Ross ◽  
Vivek Rao
Keyword(s):  
Heart Valves ◽  
Ventricular Assist Devices ◽  
Prosthetic Heart Valves ◽  
Pathological Findings ◽  
Ventricular Assist ◽  
Assist Devices

A Mathematical Model for Shear-Induced Platelet Activation in Response to Time Dependent Shear Stress Histories

2012 ◽  
Author(s):  
João S. Soares ◽  
Jawaad Sheriff ◽  
Danny Bluestein
Keyword(s):  
Platelet Activation ◽  
Heart Valves ◽  
Drug Regimen ◽  
Ventricular Assist Devices ◽  
Prosthetic Heart Valves ◽  
Thromboembolic Complications ◽  
Ventricular Assist ◽  
Blood Damage ◽  
Anticoagulant Drug ◽  
Cardiovascular Implants

The advent of blood recirculating devices and cardiovascular implants (e.g. ventricular assist devices and prosthetic heart valves) has motivated research efforts towards a better understanding of blood damage, hemolysis, and chronic platelet activation that these devices induce. Because of the latter, patients with these classes of implants still develop thromboembolic complications that expose them to a greater risk of cardioembolic stroke and mandate life-long anticoagulant drug regimen with its inherent risks.

Design Optimization of a Mechanical Heart Valve for Reducing Valve Thrombogenicity: A Case Study With ATS Valve

2010 ◽  
Author(s):  
Gaurav Girdhar ◽  
Yared Alemu ◽  
Michalis Xenos ◽  
Jawaad Sheriff ◽  
Jolyon Jesty ◽  
...  
Keyword(s):  
Heart Valves ◽  
Thrombus Formation ◽  
Anticoagulation Therapy ◽  
Mechanical Heart Valve ◽  
Ventricular Assist Devices ◽  
Circulatory Support ◽  
Ventricular Assist ◽  
Mechanical Circulatory Support Devices ◽  
Artificial Hearts

Flow past mechanical heart valves (MHV) in mechanical circulatory support devices including total artificial hearts and ventricular assist devices, is primarily implicated in thromboembolism due to non-physiological flow conditions where the elevated stresses and exposure times are sufficiently high to cause platelet activation and thrombus formation. Mitigation of this risk requires lifelong anticoagulation therapy and less thrombogenic MHV designs should therefore be developed by device manufacturers [1].

Impact of Outlet Valve Orientation on Fluid Dynamics of the 12 cc Penn State Pediatric Ventricular Assist Device

2008 ◽  
Author(s):  
Isabella E. Valenti ◽  
Breigh N. Roszelle ◽  
Michael V. Perone ◽  
Steven Deutsch ◽  
Keefe B. Manning
Keyword(s):  
Heart Valves ◽  
Thrombus Formation ◽  
Ventricular Assist Devices ◽  
Ventricular Assist ◽  
Bridge To Transplant ◽  
Penn State ◽  
Outlet Valve ◽  
Cardiovascular Defects ◽  
Interior Walls ◽  
Arteries And Veins

Congenital cardiovascular defects are the leading cause of death among live births [1]. These defects involve the interior walls of the heart, valves, arteries, and veins and change the normal flow of blood through the heart and into the systemic system. Fortunately, several options exist for the more than 35,000 children born with congenital heart disease. Ventricular assist devices (VADs) currently hold the most promise for bridge-to-transplant treatment; however, a major problem for these devices is thrombus formation and deposition.

Design Optimization of Rotary Blood Pumps: Alternatives to Anticoagulation Therapy

2011 ◽  
Author(s):  
Gaurav Girdhar ◽  
Michalis Xenos ◽  
Wei-Che Chiu ◽  
Yared Alemu ◽  
Bryan Lynch ◽  
...  
Keyword(s):  
Heart Valves ◽  
Anticoagulation Therapy ◽  
Ventricular Assist Devices ◽  
Circulatory Support ◽  
Shear Stresses ◽  
Ventricular Assist ◽  
Bridge To Transplant ◽  
Life Saving ◽  
Optimization Methodology ◽  
Rotary Blood Pumps

Mechanical circulatory support (MCS) devices such as the ventricular assist devices (VADs) provide life saving short-term bridge-to-transplant solutions (1) to a large proportion of patients who suffer from chronic heart failure. Although hemodynamically efficient, such devices are burdened with high incidence of thromboembolic events due to non-physiological flow past constricted geometries where platelets (the principal cellular clotting elements in blood) are exposed to elevated shear stresses and exposure times (2) — requiring mandatory anticoagulation. We recently developed an optimization methodology — Device Thrombogenicity Emulator (DTE)(3) — that integrates device specific hemodynamic stresses (from numerical simulations) with experimental measurements of platelet activation. The DTE was successfully applied by our group to measure / optimize the thromboresistance of mechanical heart valves (MHV) (3, 4).

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