Mechanical Heart Valves (MHVs) are known for their excellent lifespan and feasibly are the most reliable and stable valves amongst all prosthetic valves. Successful bileaflet MHVs such as the St. ...Jude Medical (SJM) are known for providing central blood flow and minimal pressure drop across the valve. However, due to their non-physiological flow conditions, they still suffer from hemodynamic complications, that is, red blood cell (RBC) lysis and/or thrombogenicity, to date. Our hypothesis is that the design of MHVs can be improved so that their hemodynamics can be comparable to those of tissue valves. In this study, a new concept for the design of MHVs is proposed. To accomplish this, we identified the major design limitations of bileaflet MHVs, such as the gold standard SJM valve as well as the believed contributing factors to their thrombogenicity. We developed a novel design architecture for bileaflet MHVs that addressed these limitations, and from it, the Apex Valve (AV). Our experimental assessment of the AV found that its hemodynamics were closer to that of a bioprosthetic valve than of a bileaflet MHV. This design has been filed as a US Provisional Patent.
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DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The objective of this study was to investigate and compare the hemodynamic and turbulence characteristics upon implantation of St Jude Medical (SJM) (St Jude Medical, St Paul, Minn) and On-X (On-X ...Life Technologies, Kennesaw, Ga) bileaflet mechanical valves. Both valves are considered highly successful bileaflet mechanical valves characterized by good clinical outcomes despite their numerous design differences. Although thromboembolism remains the main disadvantage of bileaflet mechanical valves, On-X valves have been shown to need less anticoagulation therapy.
Hemodynamic assessment of a 23-mm On-X bileaflet mechanical valve and a 23-mm bileaflet SJM valve implanted in an aortic root was performed under pulsatile physiologic conditions. Time-resolved and phase-locked particle-image-velocimetry images and high-speed imaging data were acquired. Pressure gradients, effective orifice areas, dimensionless area index, leaflet position tracking, velocity, and principal Reynolds shear stress were calculated.
Pressure gradient for the On-X valve was 4.15 ± 0.099 mm Hg versus 4.75 ± 0.048 mm Hg for SJM (P < .001). Effective orifice area for the On-X valve was 2.61 ± 0.045 cm2 versus 2.36 ± 0.022 cm2 for SJM (P < .001). Area index was higher with SJM (0.87 ± 0.008) than with On-X (0.73 ± 0.013) (P < .001). On-X showed fluctuating leaflet behavior during systole, whereas SJM leaflets were stable. At peak systole, the maximal velocity with On-X was 1.86 m/s versus 2.33 m/s with SJM. Reynolds shear stress was higher with On-X compared with SJM at peak systole (95 vs 72 Pa). Higher velocity fluctuation was noted with the On-X valve.
This study shows that despite the design differences that characterize the On-X valve, the hemodynamic and turbulence parameters were not necessarily improved compared with SJM.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
W ramach fakultetów specjalnościowych na Wydziale Pedagogiki i Psychologiiw pionie pedagogika w roku akademickim 2014/2015 uruchomionych zostało7 grup ćwiczeniowych (na 8 funkcjonujących) z ...przedmiotu „Zbliżyć się do świataciszy”– elementy języka migowego. Propozycja tego fakultetu pojawiała się w oferciepo raz pierwszy. W niniejszym artykule przedstawiono opinie studentów po zrealizowanymprzedmiocie oraz spostrzeżenia i zapatrywania nauczyciela prowadzącegowraz z wizją na kontynuowania podobnych zajęć w kolejnych latach. Konstatacjepozwolą na zoptymalizowanie prowadzonych zajęć w zakresie nauki podstawowychzwrotów w języku migowym oraz uatrakcyjnienie zajęć poprzez wykorzystanie innychtechnik pracy.
Concerns have been raised over the possible link between the growing political polarisation and fears of autocratisation in Slovenia. Faced with a lack of empirical data, we seek to answer two ...questions. First, how has political polarisation developed in Slovenia? We show that Slovenia has experienced massive increases in both ideological and affective polarisation on the levels of the citizenry and political parties. Second, what has been the effect of political polarisation on liberal democracy in Slovenia? A GLS (generalised least squares) model for the period 1992 to 2022 confirms negative effects only for affective, but not ideological polarisation regarding V-Dem’s liberal democracy and judicial constraints on the executive indices. Keywords: Slovenia, affective polarisation, ideological polarisation, autocratisation, SJM
The implantation of an improperly sized annuloplasty ring may result in an incompetent valve after surgical mitral valve repair. Consequently, the procedure of ring size selection is considered ...critical. Although a plethora of sizing strategies are described, the opinions on how to select the appropriate ring size differ widely and often appear arbitrary (ie, without scientific justification). These inconsistencies raise the question where, with respect to ring sizing, science stops and voodoo begins.
Published studies report the incidence of pannus formation with the St. Jude MedicalR prosthetic mitral valve to be 0.02%. The following report details a mitral valve malfunction due to pannus ...formation and thrombosis in a 70-year-old woman which occurred 16 months after the initial operation (SJMR 27mm) using Dacron-cuff. A second replacement using a mitral valve prosthesis (SJMR 27mm) using Teflon-cuff was successfully performed and the postperative course was uneventful. The possibility of pannus formation of St. Jude MedicalR aortic valve and its mechanism are discussed in this report.
In this study, the hemodynamic performance of the conventional St. Jude Medical (SJM) valve and our proposed design known as the oval SJM valve are studied and compared. These studies are based on a ...wide range of physiological heart rates, i.e., 70–130
bpm, in the opening phase. We designed and developed a precise computational platform to assess the hemodynamics of bileaflet mechanical heart valves for laminar and turbulent regimes. Also, as one of the fundamental changes applied to the conventional SJM vales, the housing is considered oval similar to oval shape of annulus. Results clearly indicate hemodynamic improvements in the proposed design over the SJM valve. The improvements are characterized by lower shear stress and wall shear stress distributions around the valve and leaflets, and lower valve pressure drop compared to that of the conventional SJM model. The proposed design shows potential and merits additional development.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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