Materials Characterization of Explanted Mechanical Heart Valves and Comparison to Patients’ Clinical Data

2005 ◽  
Vol 28 (7) ◽  
pp. 701-710 ◽  
Author(s):  
S. Farè ◽  
M.F. Brunella ◽  
G. Bruschi ◽  
A. Cigada ◽  
E. Vitali
Keyword(s):  
Material Properties ◽  
Heart Valves ◽  
Clinical Symptoms ◽  
Materials Characterization ◽  
Mechanical Heart Valves ◽  
Health Conditions ◽  
Critical Areas ◽  
Pyrolitic Carbon

In the present study, twelve explanted mechanical heart valves (MHVs) with pyrolitic carbon tilting disc and 14 bileaflet MHVs were analyzed to investigate the effects of material properties on valve performance and patients’ general health conditions. Optical and scanning electron microscopy was used to investigate material imperfections, wear patterns or damages to housing and occluder components. All analyzed tilting disc valves exhibited wear effects, particularly due to abrasion and impact to both disc and housing. Wear of pyrolitic carbon disc and housing did not influence their in vivo performance. In the bileaflet MHVs, breakaway of the pyrolitic carbon coating sometimes caused malfunctioning and required surgical retrieval of the valve. In all cases, occurrence of clinical symptoms was more likely when wear effects were located in critical areas. The study supports a correlation between the properties of the MHVs material and patients’ symptoms.

In-vitro characterization of flow through mechanical heart valves

2006 ◽  
Vol 39 ◽  
pp. S306 ◽  
Author(s):  
L.P. Dasi ◽  
H. Simon ◽  
L. Ge ◽  
F. Sotiropoulos ◽  
A. Yoganathan
Keyword(s):  
Heart Valves ◽  
Mechanical Heart Valves ◽  
In Vitro Characterization ◽  
Flow Through

scholarly journals Short- and long-term efficacy of aspirin and clopidogrel for thromboprophylaxis for mechanical heart valves: An in vivo study in swine

2008 ◽  
Vol 136 (4) ◽  
pp. 908-914 ◽  
Author(s):  
Stephen H. McKellar ◽  
Jess L. Thompson ◽  
Raul F. Garcia-Rinaldi ◽  
Ryan J. MacDonald ◽  
Thoralf M. Sundt ◽  
...  
Keyword(s):  
Heart Valves ◽  
Mechanical Heart Valves ◽  
In Vivo Study ◽  
Term Efficacy ◽  
Short And Long Term

In Vivo Remodeling and Structural Characterization of Fibrin-Based Tissue-Engineered Heart Valves in the Adult Sheep Model

2009 ◽  
Vol 15 (10) ◽  
pp. 2965-2976 ◽  
Author(s):  
Thomas C. Flanagan ◽  
Jörg S. Sachweh ◽  
Julia Frese ◽  
Heike Schnöring ◽  
Nina Gronloh ◽  
...  
Keyword(s):  
Structural Characterization ◽  
Heart Valves ◽  
Sheep Model ◽  
Adult Sheep ◽  
Tissue Engineered Heart Valves

A New Method for Evaluation of Cavitation Near Mechanical Heart Valves

2003 ◽  
Vol 125 (5) ◽  
pp. 663-670 ◽  
Author(s):  
Peter Johansen ◽  
Keefe B. Manning ◽  
John M. Tarbell ◽  
Arnold A. Fontaine ◽  
Steven Deutsch ◽  
...  
Keyword(s):  
High Frequency ◽  
Heart Valves ◽  
A Priori ◽  
Pressure Fluctuations ◽  
Mechanical Heart Valves ◽  
New Method ◽  
Pass Filter ◽  
Bandwidth Limitation ◽  
High Pass

Evaluation of cavitation in vivo is often based on recordings of high-pass filtered random high-frequency pressure fluctuations. We hypothesized that cavitation signal components are more appropriately assessed by a new method for extraction of random signal components of the pressure signals. We investigated three different valve types and found a high correlation between the two methods r2:0.8806−0.9887. The new method showed that the cavitation signal could be extracted without a priori knowledge needed for setting the high-pass filter cut off frequency, nor did it introduce bandwidth limitation of the cavitation signal.

In vitro characterization of bileaflet Mechanical Heart Valves closing sound

2008 ◽  
Author(s):  
A. Bagno ◽  
R. Buselli ◽  
F. Anzil ◽  
V. Tarzia ◽  
V. Pengo ◽  
...  
Keyword(s):  
Heart Valves ◽  
Mechanical Heart Valves ◽  
In Vitro Characterization

Platelet Activation in Flow Past Mechanical Heart Valves

2001 ◽  
Author(s):  
Danny Bluestein ◽  
Jolyon Jesty ◽  
Adam E. Saltman ◽  
Irvin B. Krukenkamp ◽  
Krishnamurthy Suresh
Keyword(s):  
Platelet Activation ◽  
Heart Valves ◽  
Mechanical Heart Valves ◽  
Implantation Technique ◽  
Shear Stresses ◽  
Flow Past ◽  
Activity State ◽  
Valve Implantation

Abstract Numerical studies, in vitro, and in vivo measurements were conducted, aimed at quantifying free emboli formation and procoagulant properties of platelets induced by flow past mechanical heart valves (MHV). Pulsatile turbulent flow simulation was conducted past a St. Jude medical MHV in the aortic position, to study the effects of valve implantation technique on the thromboembolic potential of the valve. A misaligned valve with subannualarly sutured pledgets produced accelerating jet flow through the valve orifices and a wider wake of shed vortices. Shear stress histories of platelets along turbulent trajectories exposed the platelets to elevated shear stresses around the leaflets, leading them to entrapment within the shed vortices. In vitro platelet studies were conducted past the MHV mounted in a recirculation flow loop, by measuring the platelets ability to support the activation of acetylated human prothrombin by factor xa, which enables sequestering flow induced effects and quantification of the platelets activity state. The platelet activation state increased monotonically as a function of the recirculation time past the valve, as measured by the thrombin generation rates in the assay. Finally, platelet activity state measurements were conducted in vivo, from a sheep with an implanted MHV, showing marked increase of platelet activation after valve implantation.

Characterization of Hemodynamic Forces Induced by Mechanical Heart Valves: Reynolds vs. Viscous Stresses

2007 ◽  
Vol 36 (2) ◽  
pp. 276-297 ◽  
Author(s):  
Liang Ge ◽  
Lakshmi P. Dasi ◽  
Fotis Sotiropoulos ◽  
Ajit P. Yoganathan
Keyword(s):  
Heart Valves ◽  
Mechanical Heart Valves ◽  
Hemodynamic Forces ◽  
Viscous Stresses

Functional characterization of human brown adipose tissue metabolism

2020 ◽  
Vol 477 (7) ◽  
pp. 1261-1286 ◽  
Author(s):  
Marie Anne Richard ◽  
Hannah Pallubinsky ◽  
Denis P. Blondin
Keyword(s):  
Adipose Tissue ◽  
Brown Adipose Tissue ◽  
Functional Characterization ◽  
Human Infants ◽  
Positron Emission ◽  
Brown Adipose ◽  
Treatment Of Obesity ◽  
And Function

Brown adipose tissue (BAT) has long been described according to its histological features as a multilocular, lipid-containing tissue, light brown in color, that is also responsive to the cold and found especially in hibernating mammals and human infants. Its presence in both hibernators and human infants, combined with its function as a heat-generating organ, raised many questions about its role in humans. Early characterizations of the tissue in humans focused on its progressive atrophy with age and its apparent importance for cold-exposed workers. However, the use of positron emission tomography (PET) with the glucose tracer [18F]fluorodeoxyglucose ([18F]FDG) made it possible to begin characterizing the possible function of BAT in adult humans, and whether it could play a role in the prevention or treatment of obesity and type 2 diabetes (T2D). This review focuses on the in vivo functional characterization of human BAT, the methodological approaches applied to examine these features and addresses critical gaps that remain in moving the field forward. Specifically, we describe the anatomical and biomolecular features of human BAT, the modalities and applications of non-invasive tools such as PET and magnetic resonance imaging coupled with spectroscopy (MRI/MRS) to study BAT morphology and function in vivo, and finally describe the functional characteristics of human BAT that have only been possible through the development and application of such tools.

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