Hydrodynamic Characteristics of Bileaflet Mechanical Heart Valves in an Artificial Heart: Cavitation and Closing Velocity

Lee, Hwansung; Homma, Akihiko; Taenaka, Yoshiyuki

doi:10.1111/j.1525-1594.2007.00419.x

Cited by 13 publications

(5 citation statements)

References 9 publications

(8 reference statements)

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“…It can be found that the time length of the saturated vapor pressure in the tube is about 210 microseconds after the moment of valve closing. Results are consistent with the experimental results of Lee [42], which prove that numerical results are correct and effective. After valve closing, the volume distributions of the vapor phase at three different times are shown in Figure 8b.…”

Section: Cavitation Characteristics Of the Bileaflet Mechanical Heartsupporting

confidence: 87%

Transient Study of Flow and Cavitation Inside a Bileaflet Mechanical Heart Valve

Gao

Jin

et al. 2020

Applied Sciences

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A mechanical heart valve (MHV) is an effective device to cure heart disease, which has the advantage of long life and high reliability. Due to the hemodynamic characteristics of blood, mechanical heart valves can lead to potential complications such as hemolysis, which have damage to the blood elements and thrombosis. In this paper, flowing features of the blood in the valve are analyzed and the cavitation mechanism in bileaflet mechanical heart valve (BMHV) is studied. Results show that the water hammer effect and the high-speed leakage flow effect are the primary causes of the cavitation in the valve. Compared with the high-speed leakage flow effect, the water hammer has a greater effect on the cavitation strength. The valve goes through four kinds of working condition within one heart beating period, including, fully opening stage, closing stage and fully closing stage. These four stages, respectively, make up 8.5%, 16.1%, 4.7% and 70.7% of the total period. The cavitation occurs on the fully closing stage. When the valve is in closing stage, the high pressure downstream of the valve lasts for about 20 ms and the high-speed leakage flow lasts for about 200 ms. This study systematically analyzes the causes of cavitation emerged in the process of periodic motion, which proposes the method for characterizing the intensity of the cavitation, and can be referred to for the cavitation suppression of the BHMV and similar valves.The main concerns of valve research have been the performance [3] and the internal flow properties [4]. In order to study the hydrodynamic characteristics of the mechanical heart valve, numerical simulation based on CFD is one powerful tool to study cardiovascular risk factors, especially those related to mechanical properties of artificial heart valve [5]. It is an effective way to improve the performance of the valve by structure optimization, which is applicable to many valves +(e.g., Tesla valve) [6,7], and the BMHV is no exception. Many works on the effect of geometric features of the BMHV on blood stream are performed by simulations in the past years. For example, it has been found that the maximum shear stress within the range of platelet activation can lead to thrombosis [8,9]. The strategy of self-adapting mesh is used to capture the motion of the leaflet realizing by user-defined functions (UDF) in the commercial software [10]. It is found that the valve leaflet and the valve pivot are continuously exposed to shear stress higher than 52.3 Pa, which can cause damage to the platelets. The problem of thrombosis can be solved by increasing the curvature of the leaflet of the bileaflet mechanical heart valve [11]. Results show that increasing the curvature of the leaflet can provide larger central circulation area and reduce the risk of thrombosis. Another way [12] is proposed by using BMHV with SH coating to reduce the interaction between blood and BMHV. Based on effect analysis of BMHV with SH coating on blood substances and hemodynamics, the performance index of BMHV with SH coating, w...

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Section: Cavitation Characteristics Of the Bileaflet Mechanical Heartsupporting

confidence: 87%

Transient Study of Flow and Cavitation Inside a Bileaflet Mechanical Heart Valve

Gao

Jin

et al. 2020

Applied Sciences

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“…Therefore, the flow becomes more uniform, the size of the wake of the leaflets decreases, and eddies around the leaflet edges become less pronounced. 19,20 It was observed that by increasing the opening angle from 80° to 85°, flow separation and stress accumulation was reduced. 21 Flow separation and vortex shedding at the trailing edge of the leaflets can be further reduced by reducing the thickness of the leaflets and streamlining their shape.…”

Section: Forward Flowmentioning

confidence: 99%

Alternative mechanical heart valves for the developing world

Wium

Jordaan

Botes

et al. 2019

Asian Cardiovasc Thorac Ann

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Due to the prevalence of rheumatic heart disease in the developing world, mechanical heart valves in the younger patient population remain the prostheses of choice if repair is not feasible. Despite their durability, mechanical valves are burdened by coagulation and thromboembolism. Modern design tools can be utilized during the design process of mechanical valves, which allow a more systematic design approach and more detailed analysis of the blood flow through and around valves. These tools include computer-aided design, manufacturing, and engineering, such as computational fluid dynamics and finite element analysis, modern manufacturing techniques such as additive manufacturing, and sophisticated in-vitro and in-vivo tests. Following this systematic approach, a poppet valve was redesigned and the results demonstrate the benefits of the method. More organized flow patterns and fewer complex fluid structures were observed. The alternative trileaflet valve design has also been identified as a potential solution and, if a similar design approach is adopted, it could lead to the development of an improved mechanical heart valve in the future. It is imperative that researchers in developing countries continue their search for a mechanical heart valve with a reduced thromboembolic risk, requiring less or no anticoagulation.

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“…When cavitation bubbles flow onward into a higher pressure region, the rapid collapse of these bubbles may generate a high-speed micro-jet and shock waves, resulting in a very high pressure. The maximum closing velocity of the leaflet has been investigated as a possible cause of cavitation in an electro-hydraulic total artificial heart with tap water [83]. Moreover, erosion pitting generated due to cavitation has been shown to be restricted to an area on the valve surface next to the edge of the valve stop where the squeeze flow occurs [83].…”

Section: Assessment Of the Biomaterials Used In The Mhvsmentioning

confidence: 99%

“…The maximum closing velocity of the leaflet has been investigated as a possible cause of cavitation in an electro-hydraulic total artificial heart with tap water [83]. Moreover, erosion pitting generated due to cavitation has been shown to be restricted to an area on the valve surface next to the edge of the valve stop where the squeeze flow occurs [83]. It is well known that for brittle materials such as LTI carbon, flaws in the form of microcracks are inevitably built into the leaflets in the manufacturing process.…”

Section: Assessment Of the Biomaterials Used In The Mhvsmentioning

confidence: 99%