• Proceedings of the KOSOMBE Conference
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• v.1994 no.05
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• pp.105-108
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• 1994

A comparative study was made of the valvular sounds produced by normal prosthetic valves with thrombosed prosthetic valves. Comparisons of the closing sound were made for the power frequency spectra associated with individual valves. We used periodogram approach to obtain the spectral characteristics of the valve. Spectral analysis system was tested in mock circulatory system by comparing normal valves with those produced by the same valves but having simulated thrombosis at the hinge of the valve. The heart sounds was recorded from two patients having normal mechanical valve and thrombosed mechanical valve. The estimated spectrum of the thrombosed mechanical valve displayed lower apparent peak frequency than that of the normal valve. The results showed that frequency spectra gave information pertinent to the valve malfunction. Sound spectral analysis is simple and alternative diagnostic tool for early detection of prosthetic valve mal function.

• 대한임상약리학회:학술대회논문집
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• 2006.11a
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• pp.47-48
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• 2006

• Proceedings of the PSK Conference
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• 2001.10a
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• pp.163.2-164
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• 2001

• Journal of Chest Surgery
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• v.46 no.5
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• pp.380-382
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• 2013

• Journal of Chest Surgery
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• v.16 no.1
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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.

• Journal of Chest Surgery
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• v.20 no.2
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• pp.223-229
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• 1987

Doppler echocardiography provides valuable information regarding prosthetic heart valve function rather than structure. There are three methods of expressing the severity of mitral valve obstruction: the transvalvular pressure gradient, effective valve area, and pressure half-time. Of these, the transvalvular pressure gradient [~p] can be determined by the measurement of maximum transvalvular blood flow velocity [V] according to the modified Bernoulli`s equation [gp=4V*]. Eleven patients, who underwent mitral valve replacement with Duromedics mechanical prostheses, and 17 normal persons were investigated. There were significantly higher calculated pressure gradients in prosthetic than normal mitral valves [9.*10*2.22mmHg-vs-3.26*0.99mmHg:p<0,01], and there was a inverse relationship between pressure gradient and prosthetic valve size [11.17*0.%mmHg in size 27mm and 29mm -v- 7.38*1.12mmHg in size 31mm and 33mm; r=0.85, p<0.01] The noninvasive Doppler technique should be useful in the diagnosis of prosthetic valve obstruction.

• Journal of Chest Surgery
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• v.19 no.4
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• pp.584-594
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• 1986

Despite the multivariate improvements in tissue treatment, material, and design of prosthetic heart valves in recent years, numerous complications that may lead to valve dysfunction remain a constant threat after valve replacement. Most common indications for prosthetic valve failure are primary valve failure, infective endocarditis, paravalvular leakage, and thromboembolism. From 1977 to 1986, 15 patients underwent reoperation for prosthetic valve failure in 278 cases of valve surgery. The etiology of prosthetic valve failure were primary valve failure in 12 patients [80 %], infective endocarditis in 2 patients [13.3 %], and a paravalvular leakage [6.7 %]. The average durations of implantation were 45.5 months; 53.9 months in primary valve failure, 16 months in infective endocarditis, and 4 months in paravalvular leakage. The rate of valve failure was high under age of 30 [11/15]. Calcifications and collagen disruption of prosthesis were main cause of primary valve failure in macro- & micropathology. Prosthesis used in reoperation were 5 tissue valves and 10 mechanical valves. Operative mortality were 13.3 % [2/15], due to intractable endocarditis and ventricular arrhythmia.

• Proceedings of the KOSOMBE Conference
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• v.1993 no.11
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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.

• Journal of Chest Surgery
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• v.21 no.1
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• pp.62-69
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• 1988

In the department of chest surgery of WonKwang university hospital, mechanical valve replacement was performed in 51 cases from June 1985 to September 1987. Among these, 32 cases were mitral valve replacement, 4 cases were aortic valve replacement, and 15 cases were double valve replacement. 26 cases were male and 25 cases were female and age distribution ranged from 16 years old to 63 years old. Early death within 30 days after operation was 2 cases [3.9%] and causes of death were right heart failure [1] and right ventricular wall rupture [1]. Among 49 early survivors, 2 cases of late death were developed and the causes of death were cardiomyopathy [1] and ventricular arrhythmia [1] Anticoagulant therapy was done with warfarin sodium to the level of 1.5-2 times of normal prothrombin time [20-40%] in 47 survivors. Symptomatically, 93.6% of preoperative NYHA functional class III or IV were converted to the NYHA functional class I or II during follow up.

• 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.