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.

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

Design of Triggering Device for VFTO Measurement System

2012 ◽  
Vol 516-517 ◽  
pp. 1759-1764
Author(s):  
Gong Chang Yue ◽  
Yu Rong Jia ◽  
Jia Xi He ◽  
Wei Dong Liu
Keyword(s):  
Measurement System ◽  
High Frequency ◽  
Measuring Process ◽  
Pass Filter ◽  
High Pass Filter ◽  
Power Frequency ◽  
Gas Insulated Substation ◽  
Disconnect Switch ◽  
Transient Overvoltage ◽  
High Pass

Very fast transient overvoltage (VFTO) can be generated during the operation of disconnect switch (DS). Especially in ultra high voltage (UHV) gas insulated substation (GIS), VFTO is a threat to the safety of the power system equipment. It is very important to measure VFTO waveforms accurately. VFTO waveforms are comprised of high frequency voltage superimposed on the power frequency voltage in source side of DS and high frequency voltage superimposed on step-wise voltage in load side. How to trigger oscilloscope to acquire data is a big problem in measuring process. According to the features of VFTO waveforms, new triggering device consisting of a high pass filter is designed. The output of measurement sensor is used as the input of the high pass filter, and the output of the high pass filter is used to trigger oscilloscope. When the DS is not operated, there are no signals output from the high pass filter and the oscilloscope is waiting for trigger. After the operation of DS, the high frequency signals will pass the filter to trigger oscilloscope to acquire data. The device can guarantee the oscilloscope to complete a data acquisition properly.

Development of a Wavelet Analytical Tool for Isolating and Evaluating Cavitation-Induced Hemolysis Generated During Mechanical Heart Valve Closure

2007 ◽  
Author(s):  
Luke H. Herbertson ◽  
Steven Deutsch ◽  
Keefe B. Manning
Keyword(s):  
Blood Cells ◽  
Heart Valves ◽  
Pressure Fluctuations ◽  
Mechanical Heart Valve ◽  
Analytical Techniques ◽  
Analytical Tool ◽  
The Body ◽  
Isolation Technique ◽  
Visual Evidence

Cavitation formed during the closure of mechanical heart valves (MHVs) can harm nearby blood cells and valve surfaces. In this study we focus on an approach to accurately measure cavitation energy in order to compare the effectiveness of replacement valves. Cavitation energy is difficult to measure acoustically because it is masked by other pressure fluctuations in the body or system. To improve upon currently used analytical techniques, a wavelet isolation technique was developed to quantify cavitation energy. With this method, acoustic signals captured by a hydrophone are decomposed, denoised, and then reconstructed. Wavelet analysis should prove to be particularly valuable in vivo, where visual evidence of cavitation cannot be obtained.

CHUA'S CIRCUIT STABILIZATION: A DAMPING INJECTION APPROACH

2005 ◽  
Vol 15 (01) ◽  
pp. 181-189 ◽  
Author(s):  
JOSE ALVAREZ-RAMIREZ ◽  
ILSE CERVANTES ◽  
JUAN-CARLOS SANCHEZ ◽  
SERGIO PEREZ
Keyword(s):  
Perturbation Methods ◽  
Equilibrium Points ◽  
A Priori ◽  
Control Performance ◽  
Pass Filter ◽  
Chua Circuit ◽  
Singular Perturbation Methods ◽  
Semiglobal Stabilization ◽  
Feedback Control Strategy ◽  
High Pass

The problem of stabilizing the Chua circuit about equilibrium points is addressed in this paper. Singular perturbation methods are used to prove that semiglobal stabilization of the circuit trajectories about equilibrium points can be achieved by means of current damping injection in a single circuit node. It is shown that such damping injection can be implemented with a standard high-pass filter. In this way, the resulting feedback control strategy has interesting robustness features since an a priori knowledge of the circuit equilibrium points is not required. Experimental work is used to illustrate the control performance.

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.

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.

305 Real-time planar spectral analysis of instantaneous high-frequency stress on blood cells behind mechanical heart valves

2007 ◽  
Vol 2006.19 (0) ◽  
pp. 60-61
Author(s):  
Daisuke ISHIKAWA ◽  
Takanobu YAGI ◽  
Hiroyuki SUDO ◽  
Shotaro WAKASA ◽  
Toshinosuke AKUTSU ◽  
...  
Keyword(s):  
Spectral Analysis ◽  
Real Time ◽  
Blood Cells ◽  
High Frequency ◽  
Heart Valves ◽  
Mechanical Heart Valves
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