Turbulent stress measurements downstream of three bileaflet heart valve designs in pigs☆

Nyboe, Camilla; Funder, Jonas Amstrup; Smerup, Morten; Nygaard, Hans; Hasenkam, J. Michael

doi:10.1016/j.ejcts.2006.03.013

Cited by 16 publications

(16 citation statements)

References 20 publications

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“…19,40 Because of the non-physiologic flow across a MHV, many researchers focused on studying the flow fields. 4,5,10,13,22,24,30,32,42,45,47 They tried to find the cause of thrombosis and hemolysis according to the threshold shear stresses mentioned above by measuring the flow fields in vitro or applying CFD to calculate shear stresses. The results showed that damage to RBCs and platelets were due to Reynolds shear stress in turbulence.…”

Section: Introductionmentioning

confidence: 99%

Estimation of Viscous Dissipative Stresses Induced by a Mechanical Heart Valve Using PIV Data

2009

Ann Biomed Eng

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Among the clinical complications of mechanical heart valves (MHVs), hemolysis was previously thought to result from Reynolds stresses in turbulent flows. A more recent hypothesis suggests viscous dissipative stresses at spatial scales similar in size to red blood cells may be related to hemolysis in MHVs, but the resolution of current instrumentation is insufficient to measure the smallest eddy sizes. We studied the St. Jude Medical (SJM) 27 mm valve in the aortic position of a pulsatile circulatory mock loop under physiologic conditions with particle image velocimetry (PIV). Assuming a dynamic equilibrium assumption between the resolved and sub-grid-scale (SGS) energy flux, the SGS energy flux was calculated from the strain rate tensor computed from the resolved velocity fields and the SGS stress was determined by the Smagorinsky model, from which the turbulence dissipation rate and then the viscous dissipative stresses were estimated. Our results showed Reynolds stresses up to 80 N/m2 throughout the cardiac cycle, and viscous dissipative stresses below 12 N/m2. The viscous dissipative stresses remain far below the threshold of red blood cell hemolysis, but could potentially damage platelets, implying the need for further study in the phenomenon of MHV hemolytic complications.

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Section: Introductionmentioning

confidence: 99%

Estimation of Viscous Dissipative Stresses Induced by a Mechanical Heart Valve Using PIV Data

2009

Ann Biomed Eng

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“…Early investigations used experimental measurements to study the flow field both in vitro 4,10,32,54,55 and in vivo. 38,39,50 Experimental techniques used for measuring the flow field include laser Doppler velocimeter (LDV) 54 and PIV. 32 In more recent years, numerical simulations are also emerging as a powerful tool for investigating BMHV flow fields.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2007

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Bileaflet mechanical heart valves (BMHV) are widely used to replace diseased heart valves. Implantation of BMHV, however, has been linked with major complications, which are generally considered to be caused by mechanically induced damage of blood cells resulting from the non-physiological hemodynamics environment induced by BMHV, including regions of recirculating flow and elevated Reynolds (turbulence) shear stress levels. In this article, we analyze the results of 2D high-resolution velocity measurements and full 3D numerical simulation for pulsatile flow through a BMHV mounted in a model axisymmetric aorta to investigate the mechanical environment experienced by blood elements under physiologic conditions. We show that the so-called Reynolds shear stresses neither directly contribute to the mechanical load on blood cells nor is a proper measurement of the mechanical load experienced by blood cells. We also show that the overall levels of the viscous stresses, which comprise the actual flow environment experienced by cells, are apparently too low to induce damage to red blood cells, but could potentially damage platelets. The maximum instantaneous viscous shear stress observed throughout a cardiac cycle is <15 N/m(2). Our analysis is restricted to the flow downstream of the valve leaflets and thus does not address other areas within the BMHV where potentially hemodynamically hazardous levels of viscous stresses could still occur (such as in the hinge gaps and leakage jets).

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“…Назначение протеза клапана сердца -беспрепятственно пропускать кровоток без потерь энер-гии и увеличения постнагрузки на миокард ЛЖ. Важно, чтобы при этом максимальные значения скоростей были близки к нормальным физиологическим, а возможность возникновения турбулентных течений крови была ми-нимизирована [18]. Основные требования к протезам клапанов сердца, как они формулируются сегодня, за-ключаются в том, чтобы сберегать структуру транспротез-ного потока, учитывая тем самым необходимость созда-ния благоприятных условий для ремоделирования ЛЖ и регресса массы миокарда [19].…”

Section: Discussionunclassified

The Assessment of Mechanical Heart Valves Stenosis in Adults After Aortic Valve Replacement: The Advantage of Full-Flow Design of Mechanical Valve

Bokeriya

Fadeev

et al. 2013

ARAMS

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internal orifice and tissue annulus diameters, the values of transprosthetic parameters (peak and mean gradients, blood flow velocities) through «CorBeat» were close to physiological values of transvalvular native aortic parameters and had a tendency to be not dependent on the size of prosthesis (p =0,63). In the article for the first time a morphometric database of geometric values of internal orifice area of normal native aortic valves in adults was used taking into account both the gender and the body surface area's of a patient. There was also used the standardized prosthesis size Z-score which represents the number of SDs by which the internal prosthesis area differs from the mean normal native aortic valve area for the patient's body surface area. The article emphasizes the need of the personal selection of the size and the type of prosthesis for any patient as well as the need for new design development of prosthetic heart valves.Key words: mechanical heart valve prostheses, prosthetic stenosis, prosthesis design efficiency, heart valves occluders, full-flow aortic mechanical heart valve prosthesis. ВведениеПри имплантации механического протеза клапана сердца (ПКС) конструктивные элементы протеза -пришивная манжета, стенки корпуса, запирающие эле-менты -занимают часть полезной площади отверстия фиброзного кольца, что приводит к повышению транс-протезных градиентов, скоростей кровотока и изменению структуры течения крови. Названные виды гемодина-мических возмущений характеризуют собой признаки конструктивного стеноза. Они особенно заметны у про-тезов малых диаметров (<23 мм) в сочетании с большой площадью поверхности тела пациента (ППТ >2,0 м 2 ). Конструктивный стеноз присущ всем типам механиче-ских клапанов сердца и наблюдается, прежде всего, в аор-тальной позиции. Выраженность гемодинамических при-знаков стеноза может быть снижена путем оптимизации конструктивного решения ПКС: увеличения площади проходного отверстия (А отв.ПКС , см 2 ) за счет уменьшения толщины стенок корпуса протеза и изменения формы

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Turbulent stress measurements downstream of three bileaflet heart valve designs in pigs☆

Abstract: Reynolds normal stress values were below 100 N/m2 for all three valve designs and the difference in design was not reflected in generation of turbulence. Hence, it is unlikely that any of the valve designs causes flow induced damage to platelets or erythrocytes.

Cited by 16 publications

References 20 publications

Estimation of Viscous Dissipative Stresses Induced by a Mechanical Heart Valve Using PIV Data

Estimation of Viscous Dissipative Stresses Induced by a Mechanical Heart Valve Using PIV Data

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

The Assessment of Mechanical Heart Valves Stenosis in Adults After Aortic Valve Replacement: The Advantage of Full-Flow Design of Mechanical Valve

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