• Journal of Chest Surgery
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• v.20 no.3
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• pp.458-472
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• 1987

A heart supplies bloods of about 15, 000 liters to each human organ in a day. A normal function of heart valves is necessary to this act of heart. The disease of heart valve develops to a narrowness of a closure, resulting in an abnormal circulation of bloods. In an attempt to eliminate the affliction of heart valves, the operation method to repair with artificial heart valves has been developed and saved numerous patients over past 30 years. This replacement operation has been performed since early 1960`s in Korea, but all the artificial heart valves used are imported from abroad with very high costs until recent years. The artificial heart valve using pyrolytic carbon has been developed at KAIST, which was proved to be stable in the mechanical performance and durability. Therefore, the in viva performance of this valve was examined through animal tests. The artificial heart valves used in this study are tilting disc type valves, in which the disc were made of graphite coated with pyrolytic carbon and the cages were made of titanium. In viva testings of these valves were performed in 12 dogs, in which right ventriculo-pulmonary arterial [Croup I] or inter-aortic [Croup IV] valved conduit was implanted using polytetrafluoroethylene conduits containing KAIST valve and aortic valve [Group II] or pulmonary valve [Croup III] was replaced by a KAIST valve with a 21mm or 19mm tissue annulus diameter. In group I and II, pre-and post-operative transvalvular pressure gradient was measured and compared with other prosthetic valves. During post operative period laboratory examination was performed including hemoglobin, hematocrit, red cell count, white cell, lactic acid dehydrogenase and platelet. The eight surviving dogs were sacrificed and autopsy was performed at 2, 6, and 8 weeks. KAIST valve has low transvalvular gradient and relatively high orifice area. Average ventriculo-aortic peak systolic transvalvular gradient was 14 mmHg in 21 mm valve and 19 mmHg in 19 mm valve. The valve has slight intravascular hemolysis effect. Thrombogenic effect of low polishing quality and eddy currents around small orifice is high. The valve has vulnerability of disc movement. These animal tests suggest that the improvement of the heart valve design, surface polishing state and prescription methods.

• Journal of Chest Surgery
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• v.24 no.10
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• pp.967-972
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• 1991

Between Feb. 1982 and July 1990, 173 patients [male: 89, female: 84] Who underwent heart valve replacement for acquired valvular heart disease on the Department of Thoracic and Cardiovascular Surgery, School of Medicine, Pusan National University, were reviewed for return to work after heart valve replacement. The replaced valve were mitral [128, 74.0%], aortic[10, 5.8%], mitral & aortic[35, 20.2%]. Two tricuspid valve replacement were excluded. Several important factors influencing the return to work were age, the employment status before surgery, the number of replaced valve, the pre - op NYHA functional class and cardiac function [ejection fraction]. These factors were closely related to the optimal time of heart valve replacement. It can be concluded that the rate of return to work and the quality of life would be improved if valve replacement were performed at an earlier stage of valvular heart disease.

• Journal of Chest Surgery
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• v.28 no.9
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• pp.817-821
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• 1995

The CarboMedics Medical valve has become our mechanical valvular prosthesis of choice because of favorable hemodynamic results that associated with marked clinical improvement and low incidence of thromboembolism after it,s uses. The data for this study was collected from August 1988 to July 1993,five years period. There were total of 57 patients[female 40,male 17 in this series with 4 isolated aortic valve,26 isolated mitral valve,11 double valve and a triple valve replacement. The mean follow up time was 32 months. Postoperatively,58% of cases were in New York Heart Association[NYHA functional class I,and mild and moderate symptoms[NYHA class II were present in 36% and there were very few patients remaining in higher functional classes. In postoperative echocardiographic study, showed marked improved cardiac function. The overall early mortality was 3.5% and the late mortality was one case after triple valve replacement due to sudden death. The causes of early death were attributed to early prosthetic valve endocarditis and heart failure.

• Journal of Mechanical Science and Technology
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• v.20 no.8
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• pp.1118-1124
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• 2006

Recently, cavitation on the surface of mechanical heart valve has been studied as a cause of fractures occurring in implanted Mechanical Heart Valves (MHVs). It has been conceived that the MHVs mounted in an artificial heart close much faster than in vivo sue, resulting in cavitation bubbles formation. In this study, six different kinds of mono leaflet and bileaflet valves were mounted in the mitral position in an Electro-Hydraulic Total Artificial Heart (EHTAH), and we investigated the mechanisms for MHV cavitation. The valve closing velocity and a high speed video camera were employed to investigate the mechanism for MHV cavitation. The closing velocity of the bileaflet valves was slower than that of the mono leaflet valves. Cavitation bubbles were concentrated on the edge of the valve stop and along the leaflet tip. It was established that squeeze flow holds the key to MHV cavitation in our study. Cavitation intensity increased with an increase in the valve closing velocity and the valve stop area. With regard to squeeze flow, the bileaflet valve with slow valve-closing velocity and small valve stop areas is better able to prevent blood cell damage than the monoleaflet valves.

• Journal of Chest Surgery
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• v.28 no.1
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• pp.23-30
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• 1995

From January 1985 to December 1992, of 1257 patients who underwent a heart valve replacement 210 [16.8% underwent reoperation on prosthetic heart valves, and 6 of them had a second valve reoperation. The indications for reoperation were structural deterioration [176 cases, 81.5% , prosthetic valve endocarditis [25 cases, 11.6% , paravalvular leak [12 cases, 5.6% , valve thrombosis [2 cases, 0.9% and ascending aortic aneurysm [1 case, 0.4% . Prosthetic valve failure developed most frequently in mitral position [57.9% and prosthetic valve endocarditis and paravalvular leak developed significantly in the aortic valve [40%, 75% [P<0.02 . Mean intervals between the primary valve operation and reoperation were 105.3$\pm$28.4 months in the case of prosthetic valve failure, 61.5$\pm$38.5 months in prosthetic valve endocarditis, 26.8$\pm$31.2 months in paravalvualr leak, and 25.0$\pm$7.0 months in valve thrombosis. In bioprostheses, the intervals were in 102.0$\pm$23.9 months in the aortic valve, and 103.6$\pm$30.8 months in the mitral valve. The overall hospital mortality rate was 7.9% [17/26 : 15% in aortic valve reoperation [6/40 , 6.5% in reoperation on the mitral prostheses [9/135 and 5.7% in multiple valve replacement [2.35 . Low cardiac output syndrome was the most common cause of death [70.6% . Advanced New York Heart Association class [P=0.00298 , explant period [P=0.0031 , aortic cross-clamp time [P=0.0070 , prosthetic valve endocarditis [P=0.0101 , paravalvularr leak [P=0.0096 , and second reoperation [P=0.00036 were the independent risk factors, but age, sex, valve position and multiple valve replacement did not have any influence on operative mortality. Mean follow up period was 38.6$\pm$24.5 months and total patient follow up period was 633.3 patient year. Actuarial survival at 8 year was 97.3$\pm$3.0% and 5 year event-free survival was 80.0$\pm$13.7%. The surgical risk of reoperation on heart valve prostheses in the advanced NYHA class patients is higher, so reoperation before severe hemodynamic impairment occurs is recommended.

• Journal of Chest Surgery
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• v.23 no.4
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• pp.617-621
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• 1990

A heart supplies blood of about 15, 000 liters to each human organ in a day. A normal function of heart valves is necessary to accomplish these enormous work of heart. The disease of heart valve develops to a narrowness of a closure, resulting in an abnormal circulation of blood. In an attempt to eliminate the affliction of heart valves, the operative method to replace with artificial heart valves has developed and saved numerous patients over past 30 years. This replacement operation has been performed since early 1960`s in Korea, but all the artificial heart valves used are imported from abroad with very high costs until recent years. New artificial heart valves have been developed in Korea Advanced Institute of Science and Technology since early 1980`s. The first developed valve was designed with a free-floating pyrolytic carbon disk that is suspended in a titanium cage. The design of the valve was tested in vitro, and in animals in 1987. The results from this study was that the eccentrically placed struts creates a major and minor orifice when the disc opens and stagnation of flow in the area of the minor orifice has led to valve thrombosis. In this work, the design of the valve was changed from a single - leaflet valve to double - leaflet one in order to resolve the problems observed in the first - year tests. Morphological and hemodynamic studies were made for the newly designed valves through the in vitro and in vivo tests. The design and partial materials of the artificial heart valve was improved comparing with first - year`s model. The disc in the valve was modified from single - leaflet to bi - leaflet, and the material of the cage was changed from titanium metal to silicon - alloyed pyrolytic carbon. A test was made for the valve in order to examine its mechanical performance and stability. Morphological and hemodynamic studies were made for the valve that had been implanted in tricuspid position of mongrel dogs. All the test animals were observed just before the deaths. A new artificial heart valve was designed and fabricated in order to resolve the problems observed in the old model. The new valve was verified to have good stability and high resistance to wear through the performance tests. The hemodynamic properties of the valve after implantation were also estimated to be good in animal tests. Therefore, the results suggest that the newly designed valve in this work has a good quality in view of the biocompatibility. However, valve thrombosis on valve leaflets and annulus were found. This morphological findings were in accordance with results of surface polishing status studies, indicating that a technique of fine polishing of the surface is necessary to develop a valve with higher quality and performance.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2410-2414
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• 2008

Human heart valves diseased by congenital heart defects, rheumatic fever, bacterial infection, cancer may cause stenosis or insufficiency in the valves. Treatment may be with medication but often involves valve repair or replacement (insertion of an artificial heart valve). Bileaflet mechanical heart valves (BMHVs) are widely implanted to replace the diseased heart valves, but still suffer from complications such as hemolysis, platelet activation, tissue overgrowth and device failure. These complications are closely related to both flow characteristics through the valves and leaflet dynamics. In this study, the physiological flow interacting with the moving leaflets in a bileaflet mechanical heart valve (BMHV) is simulated with a strongly coupled implicit fluid-structure interaction (FSI) method which is newly organized based on the Arbitrary-Lagrangian-Eulerian (ALE) approach and the dynamic mesh method (remeshing) in FLUENT. The simulated results are in good agreement with previous experimental studies. This study shows the applicability of the present FSI model to the complicated physics interacting between fluid flow and moving boundary.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.05
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• pp.402-405
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• 1997

The analysis of heart sounds is a noninvasive diagnostic method useful to diagnose heart valve function. In this paper we compared the ability of spectral analysis method for prosthetic heart valve sounds. Phonocardiograms of prosthetic heart valve were analyzed in order to derive frequency domain feature suitable for the classification of the valve state. The FFT-based methods did not provide sufficient frequency resolution to completely characterize the spectrum of prosthetic heart valve sounds. A high resolution parametric methods were shown to give superior frequency resolution. In parametric methods, all methods provide a 1st & 2nd & 3rd frequency component. But Shank method provided a most dominant frequency peak.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.643-646
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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, structural analysis is performed for the blood flow through a bileaflet mechanical heart valve. The structural static analysis is carried out to confirm the thickness minimization structural condition (minimum thickness shape of leaflet).

• Journal of Chest Surgery
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• v.11 no.3
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• pp.281-295
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• 1978

Last year in this department 100 cases of open heart surgery were done annually. This year 200 cases of open heart surgery were scheduled. During the first 6 months of this year 112 open heart surgery cases were done with 13 deaths [11.6%]. There were 72 cases of cougenital malformation with 9 operative deaths [12.5%], consisting of 23 acyanotic cases with one death [4.5%] and 49 cases of cyanotic cases with 8 deaths [16.3%]. Out of 40 tetralogy of Fallot, 6 cases expired [15%]. For 39 cases of acquired valvular heart disease and one Ebstein anomaly valves were replaced with 4 operative deaths [10%]. Single valve replacement in 33 with 3 operative deaths and double valve replacement in 7 cases with one death were noted. Two patients expired among 28 mitral valve replacement cases [7.1%]. Among 7 double valve replacement patients, consisting of 3 mitral and aortic and 4 mitral and tricuspid valve replacement one case expired. In a case of Ebstein anomaly, tricuspid valve was replaced with plication of atrialized right ventricle successfully. The operative result was excellent.