scholarly journals Characterization of Turbulent Flow Behind a Transcatheter Aortic Valve in Different Implantation Positions

2022 ◽  
Vol 8 ◽  
Author(s):  
Leonardo Pietrasanta ◽  
Shaokai Zheng ◽  
Dario De Marinis ◽  
David Hasler ◽  
Dominik Obrist
Keyword(s):  
Aortic Valve ◽  
Flow Field ◽  
Turbulent Flow ◽  
Aortic Root ◽  
Flow Topology ◽  
Transcatheter Aortic Valve ◽  
Long Term Performance ◽  
Term Performance

The development of turbulence after transcatheter aortic valve (TAV) implantation may have detrimental effects on the long-term performance and durability of the valves. The characterization of turbulent flow generated after TAV implantation can provide fundamental insights to enhance implantation techniques. A self-expandable TAV was tested in a pulse replicator and the three-dimensional flow field was extracted by means of tomographic particle image velocimetry. The valve was fixed inside a silicone phantom mimicking the aortic root and the flow field was studied for two different supra-annular axial positions at peak systole. Fluctuating velocities and turbulent kinetic energy were compared between the two implantations. Velocity spectra were derived at different spatial positions in the turbulent wakes to characterize the turbulent flow. The valve presented similar overall flow topology but approximately 8% higher turbulent intensity in the lower implantation. In this configuration, axial views of the valve revealed smaller opening area and more corrugated leaflets during systole, as well as more accentuated pinwheeling during diastole. The difference arose from a lower degree of expansion of the TAV's stent inside the aortic lumen. These results suggest that the degree of expansion of the TAV in-situ is related to the onset of turbulence and that a smaller and less regular opening area might introduce flow instabilities that could be detrimental for the long-term performance of the valve. The present study highlights how implantation mismatches may affect the structure and intensity of the turbulent flow in the aortic root.

Long-term performance of the Hancock bioprosthetic conduit for aortic root replacement

2008 ◽  
Vol 56 (S 1) ◽  
Author(s):  
CC Badiu ◽  
W Eichinger ◽  
D Ruzicka ◽  
I Hettich ◽  
S Bleiziffer ◽  
...  
Keyword(s):  
Aortic Root ◽  
Aortic Root Replacement ◽  
Long Term Performance ◽  
Term Performance

15 years experience with 615 homograft and autograft aortic valve replacements

1980 ◽  
Vol 3 (3) ◽  
pp. 168-172 ◽  
Author(s):  
W.H. Wain ◽  
R. Greco ◽  
A. Ignegeri ◽  
E. Bodnar ◽  
D.N. Ross
Keyword(s):  
Aortic Valve ◽  
Valve Replacement ◽  
Pulmonary Valve ◽  
Alternative Methods ◽  
Homograft Valve ◽  
Long Term Performance ◽  
Term Performance

Homograft valve replacement of the diseased aortic valve with a homologous aortic valve inserted in the sub-coronary position was first performed in July 1962 (Ross 1962). The procedure of transferring the patients autologous pulmonary valve to the aortic position has been used since 1967 (Ross 1967). The long term performance of homograft valves has not been regarded as satisfactory in some centres (Cope-land 1977, Anderson & Hancock 1977) whereas others have shown it to be an excellent valve replacement (Barratt-Boyes, 1977, Bodnar et al 1979). The differing experiences may be the results of alternative methods of sterilization, preservation and surgical insertion. This paper presents information on isolated aortic valve replacements with either homograft or autograft valves over a 15 year period.

Characterization of Aortic Root Compliance at Different Heights

2008 ◽  
Author(s):  
Eric M. Sirois ◽  
Tsuicheng Chiu ◽  
Martin Fox ◽  
Wei Sun
Keyword(s):  
Aortic Valve ◽  
Aortic Root ◽  
Heart Surgery ◽  
Severe Aortic Stenosis ◽  
Open Heart Surgery ◽  
Significant Risk ◽  
Access Site ◽  
Serious Adverse Events

Aortic valve stenosis is a significant cause of morbidity and mortality [1]. Currently, the preferred treatment of severe aortic stenosis is aortic valve replacement, which carries a significant risk for patients with comorbidities [2]. Recently, percutaneous aortic valve (PHV) replacement represents an endovascular alternative to conventional open heart surgery without the need for sternotomy, aortotomy, or cardiopulmonary bypass [3]. However, there are significant serious adverse events associated with the percutaneous procedure, such as myocardial infarction, peripheral embolism, injury to the aorta, perivalvular leak and access site injury [3–5]. Furthermore, long-term durability and safety of these valves need to be evaluated and studied carefully. We hypothesize that the device (dys)function could be more accurately predicted if a better understanding of the biomechanical interaction between the native aortic valve/root and the PHV were available. In this study, our objective is to characterize the mechanical properties of the aortic root such that its interaction with the PHV device can be quantified.

Correlating Laboratory Conditioning with Field Aging for Asphalt using Rheological Parameters

2020 ◽  
Vol 2674 (5) ◽  
pp. 393-404 ◽  
Author(s):  
Runhua Zhang ◽  
Jo E. Sias ◽  
Eshan V. Dave
Keyword(s):  
Asphalt Binder ◽  
Life Time ◽  
Rheological Parameters ◽  
Performance Grade ◽  
Wide Range ◽  
Binder Aging ◽  
Long Term Performance ◽  
Term Performance

Aging has a significant effect on performance of asphalt materials. Reliable characterization of asphalt binder properties with aging is crucial to improving asphalt binder specifications as well as modification and formulation methods. The objective of this study is to correlate the laboratory conditioning methods with field aging using evolution of binder rheological parameters with time and pavement depth. Loose mixtures are aged in the lab (5 and 12 days aging at 95°C, and 24 h at 135°C) and recovered binder rheological properties are compared with those from different layers of field cores. The virgin binder results with 20 h pressure aging vessel (PAV) aging are also included. Binder testing is conducted using a dynamic shear rheometer with a 4 mm plate over a wide range of frequencies and temperatures. Rheological parameters calculated from the master curves, performance grade system, and binder Christensen–Anderson–Marasteanu model are used to evaluate changes with aging. The field aging gradient is evaluated, and the laboratory conditioning durations corresponding with the field aging durations at different pavement depths are calculated. The results show that 5 days of aging can simulate around 8 years of field aging (in New Hampshire) for the top 12.5 mm pavement, and 12 days’ aging can simulate approximately 20 years; 20 h PAV binder aging is not adequate to capture the long-term performance of the pavement. This study provides a way to optimize the laboratory conditioning durations and evaluate the performance of asphalt material with respect to pavement life (time) and depth (location) within the pavement structure.

Characterization of the Charging and Long Term Performance of Cytop Electret Layers for MEMS Applications

2008 ◽  
Vol 1134 ◽  
Author(s):  
Ulrich Bartsch ◽  
Joao Gaspar ◽  
Oliver Paul
Keyword(s):  
Corona Discharge ◽  
Silicon Substrates ◽  
Charging Station ◽  
Corona Charging ◽  
Initial Charge ◽  
Charge Stability ◽  
Long Term Performance ◽  
Term Performance

AbstractThis paper reports on the characterization of the charge stability of an amorphous fluoropolymer electret called Cytop. Cytop is a dissolved polymer material, compatible with standard micromachining fabrication technologies. In this study, Cytop layers are deposited and patterned on Pyrex and silicon substrates, followed by the electrical poling of the material by corona discharge using a customized charging station. The long-term performance of Cytop as an electret material is evaluated as a function of several relevant charging parameters. The results reveal highly stable layers, able to keep at least 92% of the initial charge 143 days after the corona charging stored at 23°C.

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