• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1997년도 춘계학술대회
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• pp.51-54
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• 1997

Lumbrokinase, potent fibrinolytic enzyme purified from earthworm, was immobilized onto the total artificial heart valves using photoreaction. This valve were implanted into the lamb for three days. After experiments, thrombus was observed in the untreated valves whereas no thrombus was observed in the lumbrokinase immobilized valves. The fibrinolytic activity and proteolytic activity of the implanted valve was examined. The fibrinolytic activity of the valve was remained after the implantation. The lumbrokinase could be a suitable fibrinolytic agents in the vascular contacting devices to reduce the thrombus.

• 대한기계학회논문집B
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• 제26권5호
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• pp.629-639
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• 2002

In-vitro flow characteristics downstream of a polyurethane artificial heart valve and a Bjork-Shiley Monostrut mechanical valve have been comparatively investigated in pulsatile flow using particle image velocimetry (PIV). With a triggering system and a time-delayed circuit the velocity distributions on the two perpendicular measurement planes downstream of the valves are evaluated at any given instant in conjunction with the opening behaviors of valve leaflets during a cardiac cycle. The regions of stasis and high shear stress can be found simultaneously by examining the entire view of the instantaneous velocity and Reynolds shear stress fields. It is known that high shear stress regions exist at the interface between strong axial jet flows along the wall and vortical flows in the central area distal to the valves. In addition. there are large stagnation or recirculation regions in the vicinity of the valve leaflet, where thrombus formation can be induced by accumulation of blood elements damaged in the high shear stress zones. A correlation between the unsteady flow patterns downstream of the valve and the corresponding opening postures of the polyurethane valve membrane gives useful data necessary for improved design of the frame structure and leaflet geometry of the polyurethane valve.

• 대한의용생체공학회:의공학회지
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• 제15권4호
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• pp.489-497
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• 1994

The most serious problems related to the cardiovascular prothesis are thrombosis and hemolysis. It is known that the flow pattern of cardiovascular prostheses is highly correlated with thrombosis and hemolysis. Laser Doppler Anemometry (LDA) is a usual method to get flow pattern, which is difficult to operate and has narrow measure region. Particle Image Velocimetry (PIV) can solve these problems. Because the flow speed of valve is too high to catch particles by CCD camera, high-speed camera (Hyspeed : Holland-Photonics) was used. The estimated maximum flow speed was 5m/sec and maximum trackable length is 0.5 cm, so the shutter speed was determined as 1000 frames per sec. Several image processing techniques (blurring, segmentation, morphology, etc) were used for the preprocessing. Particle tracking algorithm and 2-D interpolation technique which were necessary in making gridrized velocity pronto, were applied to this PIV program. By using Single-Pulse Multi-Frame particle tracking algorithm, some problems of PIV can be solved. To eliminate particles which penetrate the sheeted plane and to determine the direction of particle paths are these solving methods. 1-D relaxation fomula is modified to interpolate 2-D field. Parachute artificial heart valve which was developed by Seoul National University and Bjork-Shiely valve was testified. For each valve, different flow pattern, velocity profile, wall shear stress and mean velocity were obtained.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1993년도 추계학술대회
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• pp.99-103
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• 1993

A monoleaflet polymer artificial heart valve which showed the remarkable improvement in pressure drop compared with other types of artificial valve was designed to decrease the deflection in vertical direction and the displacement or the valve tip in horizontal direction. Stress distribution change was studied as the location of the supporting members or the valve frame changed. And it was found that using the valve tip horizontal displacement the minimum valve thickness could be obtained in order to prevent the gap between the valve tip and the frame wall.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1993년도 추계학술대회
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• pp.104-106
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• 1993

Some cardio-vascular assist systems need more inexpensive artificial heart valves for short-term use. To meet with this need, we have developed a new polymer valve that is very simple to manufacture and of which its dimensions are easy to change, depending on its application. We have tested the hydrodynamic performance of the new polymer valve using a mock circulatory testing system and studied the flow through the valve using high-speed camera combined with image processing techniques. The results show that this valve is superior in its performances to the other valves (Bjork-Shiley mechanical valve and trileaflet polymer valve) and have no stagnation points. We also have tested the hemolytic potential of the valve. The valve is less hemolytic than the Bjork-shiley mechanical valve finally, we have applied this valve to a left ventricular assist device that we are developing.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1998년도 추계학술대회
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• pp.247-248
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• 1998

The effect of unattached valve leaflet on flow field downstream of a floating and flapping polyurethane heart valve prosthesis was investigated. With a triggering system and a time-delay circuit the instantaneous velocity field downstream of the valve was measured by particle image velocimetry (PIV) in conjunction with the opening posture of a flexible valve leaflet during a cardiac cycle. Reynolds shear stress distribution was calculated from the velocity fields and wall shear stress was directly measured by hot-film anemometry (HFA). The floating motion of the valve leaflet resulted in the reduction of pressure drop and recirculating flow region downstream of the valve.

• Journal of Chest Surgery
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• 제16권1호
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• pp.10-17
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• 1983

Valve replacement in children, aging up to 15 years [Mean 11.g years], has been done at Seoul National University Hospital over the past 14 years since 1968. Fifty-one patients have received 59 artificial valves: 55 bioprosthetic and 4 prosthetic valves. Thirty-one patients [60.8%] had rheumatic heart disease and the remainder [39.2%] had congenital heart disease. Forty-two patients [82.4%] survived operation: 9 patients [17.7%] died within one monfi3 postoperatively and 4 patients [7.8%]during the follow-up period with the overall mortality rate of Thromboembolic complication occurred in 3 patients with 2 deaths: 5.9% embolic rate or 4.68% emboli per patient-year. One patient who had been on coumadin anticoagulation died from cerebral hemorrhage. One mitral Ionescu-Shiley valve failed 19 months after first replacement and this was successfully re-replaced with the same kind of valve. Actuarial survival rate was 59.9% at 4 years after surgery. Thromboembolism-free and valve failure-free survivals were 80.0% and 93.1% respectively. These clinical results in the pediatric age group suggested that valve replacement in children was a serious undertaking with a higher mortality rate than in adults. However, the main superiority on the low thrombogenecity of the xenograft valve over the mechanical one warrants its continuing use until the question of its durability would otherwise be answered by a further study of clinical follow-up.

• 대한의용생체공학회:의공학회지
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• 제18권2호
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• pp.147-156
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• 1997

Various prosthetic heart valves have been developed and used clinically, but they have problems, such as thrombogenecity, hemoltsis, high cost and low durability. New types of trileaflet polymer heart valves have been developed in order to use them as inlet and outlet valves in a ventricular assist device. The aim of this study is to determine the hydrodynamic effectiveness of the newly designed trileaflet polymer valves and their feasibility for temporary use in the blood pumps. Trileaflet polymer valves are made of polyurethane, because of its good blood compatibility, high tonsil strength and good resistance to fatigue. An in vitro experimental investigation was perf'ormed in order to ev91ua1e hydrodynamic performance of the trileaflet polymer valves having different design and fabrication tech- niques. The St. Jude Medical valve (SJMV) and floating-type monoleaflet polymer valve (MLPV) were also tested The pressure drop across the valve, leakage volume, and the flow patterns mere investigated for valves. The result of comparative tests showed that the trileaflet polymer valves had a better hydrodynamic performance than the others. TPV which has two stable membrane shape showed the lowest back flow. The pressure hops of TPVs were lower than that of MLPV, but slightly higher than SJMV. The hydrodynamic performance of valves under the pulastile flow showed the similar results as steady flow. The velocity profiles and turbulent intensities were measured at the distal sites of valves using a hot-film anemometer. Central flow was maintained in trileaflet polymer valves, and the maximum turbulent intensities were lower in TPVs comparing to MLPV.

• Journal of Chest Surgery
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• 제27권6호
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• pp.444-450
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• 1994

From June 1984 to February 1994, cardiac valve replacement was performed in 108 patients. The distribution of patients was ranged from 13 to 64 year-old age[mean 39.48 1.24] and 51 patients were male, 57 patients were female [male:female=1:1.1]. 64 patients had mitral valve replacement, 27 patients underwent aortic valve replacement and 17 patients were performed double[mitral & aortic] valve replacement. Total 125 artificial cardiac valves were used, mechanical valves were 51 valves and tissue valves were 74 valves. The duration of follow-up was 473.41 patient-year[mean 4.79 3.29 patient-year] and the information of follow-up was available for 99 patients[92%]. The actuarial survival rates including the operative mortality was 89.5% & 88.3 at postoperative fourth & ninth year. The probability of freedom from overall valve failure, thromboembolism and bacterial endocarditis were 77.5%, 89.2% and 95.6% at ninth year after cardiac valve replacement.

• Journal of Chest Surgery
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• 제55권2호
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• pp.177-179
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• 2022

Barlow's disease with mitral annular calcification encompassing the subvalvular apparatus, including the valve leaflet and chordae, is extremely rare, and mitral valve repair in such cases is challenging. We report a case of a 60-year-old woman with mitral valve regurgitation that was successfully controlled by resecting the rough zone of P2 and calcifications on the excess leaflet regions and subvalvular apparatus, while retaining the calcification of P3 and implanting artificial chordae and an annuloplasty ring. Mitral valve repair for such cases requires an individualized and compounded surgical strategy for the technique to treat Barlow's disease and manage calcification to control mitral regurgitation.