• Korean Journal of Computational Design and Engineering
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• v.6 no.1
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• pp.59-68
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• 2001

This paper investigates the structural analysis and design of mechanical heart valve through the numerical analysis methodology. In a numerical analysis methodology application to the thickness minimization structural design of mechanical heart valve, fluid analysis is performed for the blood flow through a bileaflet mechanical heart valve. Simultaneously the kinetodynamic analysis is carried out to obtain the appropriate structural condition for the structural analysis. Thereafter the structural static analysis is also carried out to confirm the thickness minimization structural condition(minimum thickness shape of leaflet).

• Journal of Biomedical Engineering Research
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• v.12 no.3
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• pp.149-156
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• 1991

In this paper, fluttering behavior of mechanical bileaflet heart valve prosthesis was analyzed taking into consideration of the impact between valve plate and stopper Vibration system of the valve was modeled as a rotating system, and equations are induced by moment equilibrium equations. Lift force, drag force, gravity and buoyancy were considered as external forces acting on the valve plate/ The 4th order Runge-Kutta method was used to solve the equations. Valve plate does not come to the static equilibrium position at a stretch, but come to that position after under damping vibration. Damping ratio increases as the cardiac optput increases, and the mean damping ratio is in the range of 0.16~40.25. Fluttering frequency does not have any specific value, but varies as a function of time. It is in the range of 10~40Hz. Valve opening appears to be affected by the orientation of the of the valve relative to gravitational forces.

• The KSFM Journal of Fluid Machinery
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• v.7 no.3 s.24
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• pp.14-22
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• 2004

Bileaflet mechanical valves have the complications such as hemolysis and thromboembolism, leaflet damage, and leaflet break. These complications are related with the fluid velocity and shear stress characteristics of mechanical heart valves. The first aim of the current study is to introduce fluid-structure interaction method for calculation of unsteady and three-dimensional blood flow through bileaflet valve and leaflet behavior interacted with its flow, and to overcome the shortness of the previous studies, where the leaflet motion has been ignored or simplified, by using FSI method. A finite volume computational fluid dynamics code and a finite element structure dynamics code have been used concurrently to solve the flow and structure equations, respectively, to investigate the interaction between the blood flow and leaflet. As a result, it is observed that the leaflet is closing very slowly at the first stage of processing but it goes too fast at the last stage. And the results noted that the low pressure is formed behind leaflet to make the cavitation because of closing velocity three times faster than opening velocity. Also it is observed some fluttering phenomenon when the leaflet is completely opened. And the rebounce phenomenon due to the sudden pressure change of before and after the leaflet just before closing completely. The some of time-delay is presented between the inversion point of ventricle and aorta pressure and closing point of leaflet. The shear stress is bigger and the time of exposure is longer when the flow rate is maximum. So it is concluded that the distribution of shear stress at complete opening stage has big effect on the blood damage, and that the low-pressure region appeared behind leaflet at complete closing stage has also effect on the blood damage.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.185-186
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• 2008

• Journal of Mechanical Science and Technology
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• v.15 no.5
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• pp.613-622
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• 2001

Interaction of blood flow and leaflet behavior in a bileaflet mechanical heart valve was investigated using computational analysis. Blood flows of a Newtonian fluid and a non-Newtonian fluid with Carreau model were modeled as pulsatile, laminar, and incompressible. A finite volume computational fluid dynamics code and a finite element structure dynamics code were used concurrently to solve the flow and structure equations, respectively, where the two equations were strongly coupled. Physiologic ventricular and aortic pressure waveforms were used as flow boundary conditions. Flow fields, leaflet behaviors, and shear stresses with time were obtained for Newtonian and non-Newtonian fluid cases. At the fully opened phase three jets through the leaflets were found and large vortices were present in the sinus area. At the very final stage of the closing phase, the angular velocity of the leaflet was enormously large. Large shear stress was found on leaflet tips and in the orifice region between two leaflets at the final stage of closing phase. This method using fluid-structure interaction turned out to be a useful tool to analyze the different designs of existing and future bileaflet valves.

• Journal of Chest Surgery
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• v.25 no.2
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• pp.137-148
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• 1992

Until March 1991, 435 St. Jude Medical valves and 330 CarboMedics valves were implanted in 358 and 251 patients, respectively. 300 patients were male and 309 were female with the mean age of 35.6 years[from 2 month to 68 years]. 458 valves were implanted in the mitral, 272 in the aortic, 25 in the tricuspid, and 10 in the pulmonic position. Postoperatively, all patients except for very young patients were given coumadin with or without dipyridamole for anticogulation Operative mortality was 7.3%[45 deaths per 618 operations]. A total follow-up of 1244.8 patient-years was achieved for the operative survivors with a follow-up rate of 96.8%, [mean follow-up period=26.3 months /patient, ranging from 1 to 80 months]. Functional improvement was evident; 66.7% of these patients were in NYHA functional class III or IV preopratively, whereas 98.4% are in class I or II pos-toperatively. There occurred 13 late deaths[7 valve-related] and 55 valve-related complications. Linearized rates of late death and valve-related complications were 1.0%/ patient-year, 4.42%/patient-year, respectively. Rates of thromboembolism, anticoagluation-related hemorrhage were 1.12%/patient-year, 1.69% /patient-year, respectively. Actuarial survival at 5 years is 96.0% and complication-free survival at 5 years is 83.9%. No difference in survival and incidence of complications was found between the St. Jude and CarboMedics valves. On the basis of this experience, we believe that the pyrolytic carbon bileaflet mechanical valves are safe and preferable choice among current valve prostheses.

• Journal of Biomedical Engineering Research
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• v.27 no.6
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• pp.418-426
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• 2006

In the artificial heart application, productivity and hemodynamic properties of artificial heart valves are crucial in successiful application to long term in vivo trials. This paper is about manufacture and assessment of trileaflet polymer heart valves using vacuum forming process(VFP). The VFP has many advantages such as reduced fabrication time, reproducibility due to relatively easy and simple process for manufacturing. Prior to VFP of trileaflet polymer heart valves, polyurethane(Pellethane 2363 80AE, Dow Chemical) sheet was prepared by extrusion. The sheets were heated and formed to mold shape by vacuum pressure. The vacuum formed trileaflet polymer heart valves fabrication is composed of two step method, first, leaflet forming and second, conduit forming. This two-step forming process made the leaflet-conduit bonding stable with any organic solvents. Hydrodynamic properties and hemocompatibility of the vacuum formed trileaflet polymer heart valves was compared with sorin bicarbon bileaflet heart valve. The percent effective orifice area of vacuum formed trileaflet polymer heart valves was inferior to bileaflet heart valve, but the increase of plasma free hemoglobin level which reflect blood damage was superior in vacuum formed trileaflet polymer heart valves Vacuum formed trileaflet polymer heart valves has high productivity, and superior hemodynamic property than bileaflet heart valves. Low manufacturing cost and blood compatible trileaflet polymer heart valves shows the advantages of vacuum forming process, and these results give feasibility in in vivo animal trials in near future, and the clinical artificial heart development program.

• Journal of Chest Surgery
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• v.40 no.1 s.270
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• pp.63-65
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• 2007

Incidence of valve leaflet escape after mechanical valve replacement is very low. We report a case of leaflet fracture and escape in an Edwards TEKNA bileaflet valve.

• Journal of Mechanical Science and Technology
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• v.17 no.7
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• pp.1073-1082
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• 2003

Many researchers have investigated the blood flow characteristics through bileaflet mechanical heart valves using computational fluid dynamics (CFD) models. Their numerical approach methods can be classified into three types; steady flow analysis, pulsatile flow analysis with fixed leaflets, and pulsatile flow analysis with moving leaflets. The first and second methods have been generally employed for two-dimensional and three-dimensional calculations. The pulsatile flow analysis interacted with moving leaflets has been recently introduced and tried only in two-dimensional analysis because this approach method has difficulty in considering simultaneously two physics of blood flow and leaflet behavior interacted with blood flow. In this publication, numerical calculation for pulsatile flow with moving leaflets using a fluid-structure interaction method has been performed in a three-dimensional geometry. Also, pulsatile flow with fixed leaflets has been analyzed for comparison with the case with moving leaflets. The calculated results using the fluid-structure interaction model have shown good agreements with results visualized by previous experiments. In peak systole. calculations with the two approach methods have predicted similar flow fields. However, the model with fixed leaflets has not been able to predict the flow fields during opening and closing phases. Therefore, the model with moving leaflets is rigorously required for advanced analysis of flow fields.

• Journal of Chest Surgery
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• v.25 no.12
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• pp.1404-1415
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• 1992

To understand the factors influencing Atrial fibrillation and embolism in mitral valve surgery and prevent their risk, we have reviewed our 324 patients who underwent mitral valve surgery from Fev. 1982 to May 1992. Age, disease duration, lesion type, left ventricular function and left atrial dimension were chosen as preoperative factors influencing the incidence of atrial fibrillation and embolism and their postoperative course, The number and type of replaced valve, site of atriotmy, LA obliteration, ACT and use of Defibrillator were chaser. as operative factors influencing postoperative rhythm change and postop emb-olization. The results of analyses were as follows 1. The incidence of preoperative atrial fibrillation, systemic embolism and LA throbmus was 63. 6%, 10.56% and 19.8% relatively. 2. The preoperative factors of atrial fibrillation onset was old age, prolonged symptom duration, stenotic lesion, lager LAD and lower ejection fraction. In the preoperative systemic embolism preoperative factors were old age, female, stenotic lesion. The left atrial thrombus found more commonly in patients with atrial fibrillation, old age, prolonged symptom duration, stenotic lesion and low ejection fraction. 3. The preoperative atrial fibriation persisted postoperatively in 165[50.9%] and converted to normal sinus rhythm in 50[15.4%]. The preoperative normal sinus rhythm per-eisted in 100[31%] and atrial fibrillation was occured postoperatively in 9[2.7%]. The prolonged symptom duration was the preoperative factor of persist atrial fibrillation. 4. Among 95 long term follow-up patients, atiral fibrillation was continued in 59[60%]. Conversion to normal sinus rhythm was more common significantly in left atriotomy and bileaflet valve replacement. 5. There were 12 patients who had postoperative embolism. Female, persist atrial fibrillation, no LA olbiteration and tilting disc monocusp valve were considered as possible factors influencing postoperative embolism but was impossible to analyse their statistical significance due to small sample size. So we have concluded that the patients with above risk factors need anticoagulant and early surgical intervention. Left atriotomy with minimal atrial injury, left auricular obliteration and bileaflet valve replacement may be needed to reduce postoperative atrial fibrillation persist and embolism.