• Journal of Chest Surgery
• /
• 제20권3호
• /
• pp.458-472
• /
• 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.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2008년도 추계학술대회B
• /
• pp.2410-2414
• /
• 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.

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

• 대한의용생체공학회:의공학회지
• /
• 제27권6호
• /
• pp.418-426
• /
• 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 Mechanical Science and Technology
• /
• 제20권8호
• /
• pp.1118-1124
• /
• 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
• /
• 제26권4호
• /
• pp.282-293
• /
• 1993

From Sep. 1985 to Dec. 1992, total 1000 cases of open heart surgery [OHS] were performed in the department of Thoracic & Cardiovascular Surgery, Pusan Paik Hospital, College Of Medicine, Inje University.Among the total 1,000 cases of OHS, there were 823 cases with congenital heart diseases [CHD] and 177 cases with acquired heart diseases [AHD]. The age distribution was 9 days [4.0 kg] to 49 years in CHD and 11 to 64 years in AHD, In the 823 cases of CHD, there were 763 acyanotic cases and 60 cyanotic cases. The CHD cases consisted of 520 VSD [63.2 %], 177 ASD [21.5 %], 60 TOF[7.3 %], 27 PS [3.3 %], 17 ECD [2.1%], 7 Valsalva sinus rupture [0.9 %], 4 TGA [0.5 %], 3 Ebstein`s anomaly [0.4%], 3 DORV[0.4%], and others. The corrective operations were applied for congenital heart disease with the result of 2. 8 % hospital mortality. In the 177 AHD, 168 cases were valvular heart diseases, 7 cases were cardiac tumors and one LA thrombus and one annuloaortic ectasia. In the 168 valvular heart diseases, there were 115 single valve replacement cases [16 AVR, 99 MVR], 20 cases of double valve replacement[AVR & MVR], 15 cases of MVR with TVA, and 10 cases of AVR, MVR with TVA. The total implanted prosthetic valves were 199`. In MVR, 66 of St. Jude Medical valves, 78 ofCarpentier-Edward valves, and 5 of Ionescu-Shiley valves were used. In AVR, 38 of St. Jude Medical valves and 12 of Carpentier-Edward valves were used.The hospital operation mortality rate of congenital acyanotic, cyanotic, and acquired heart diseases were 1.6%, 18.3 % and 3.4% respectively. The overall mortality rate was 2.9 % [29/1000].

• Journal of Chest Surgery
• /
• 제23권4호
• /
• pp.617-621
• /
• 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.

• Journal of Chest Surgery
• /
• 제19권4호
• /
• pp.644-662
• /
• 1986

Seventy cases of open heart surgery were performed in the department of Thoracic and Cardiovascular Surgery, Pusan Paik Hospital, Inje College, from Oct. 1985 to Oct. 1986. And the results were summarized as follows. 1. Among the 70 cases, there were 48 cases of congenital heart anomalies and 22 cases of acquired rheumatic valvular heart diseases. Age range of the congenital patients was 7 months to 31 years with the mean age of 10 years, and the acquired patients was 18 to 62 years with the mean age of 40 years. 2. The heart-lung machine used for cardiopulmonary bypass was Sarns 7000, 5-head roller pump, and the number and type of oxygenators were 5 of membrane type and 65 of bubble type. For all cases GIK [glucose-insulin-potassium] solution was used as cardioplegic solution for myocardial protection during operation. 3. Among the 48 congenital anomalies, there were 12 cases of ASD group, 29 of VSD group, 3 of ECD, 3 of TOF and one of PDA + MR, and to all of which the appropriate radical operations were applied. 4. Among the 22 acquired valvular diseases, there were 11 cases of mitral valve diseases [MS; 4, MSr; 3, MRs; 4], 3 cases of aortic valve diseases [AR:1, ARs;1, ASr;1], 4 cases of double valve diseases [MRs+TR; 3, MRs+ARs; 1] and 4 cases of triple valve diseases [MSr+ASr+TR; 3, MSr+Ar+TR; 1]. To all the diseased mitral and aortic valves, artificial valve replacement was applied except one [As], in which valve plication was applied. And to all the diseased tricuspid valve, DeVega annuloplasty was applied. 5. The number of replaced artificial valves were 29 in 25 patients [congenital; 3, acquire; 22]. In MVR, 6 of mechanical valves [St. Jude Medical valve; 6] and 15 of tissue valves [Carpentier-Edward valve; 11, lonescu-Shiley valve; 4] were used. In AVR, 6 of mechanical valves [St. Jude Medical valve; 6] and 2 of tissue valves [Carpentier-Edward valve; 2] were used. 6. Postoperative complications were occurred in 12 cases. Among them 11 cases were recovered with intensive cares, but one patient [VSD + Fistula of Valsalva sinus] was expired with low cardiac out put syndrome.

• Journal of Chest Surgery
• /
• 제24권4호
• /
• pp.404-420
• /
• 1991

Surgical treatment of congenital and acquired heart disease preceded the development of accurate techniques for diagnosis, heart lung machine and cardiopulmonary bypass, intraoperative myocardial protection, operative techniques and cardiac anesthesia. For 5 years from Sep. 1985 to Sep. 1990, six hundred cases of open heart surgeries [OHS] were performed in the department of Thoracic & Cardiovascular Surgery, Pusan Paik Hospital, College of Medicine, Inje University. The results were summarized as follows. 1. The annual number of OHS[cases per year] was above 100 since 1987, and the increasing rate of cases was 23.5% per year since 1986. 2. Among the total 600 cases, there were 470 cases of congenital heart diseases and 130 cases of acquired. Age range of the congenital patients was 8 months to 44 years with the mean age of 10 years, and acquired patients was 16 to 56 years with the mean age of 36 years. 3. Among the 470 congenital anomalies, there were 429 cases of acyanotic and 41 cyanotic patients. Totally, VSD was 286 cases[60.6%], ASD 103 cases[21.9%], TOF 35 cases [7.4%], PS 20 cases [4.1%], ECD 12 cases [2.0%], Ebstein`s anomaly 3 cases [0.6%], Valsalva sinus rupture 3 cases [0.6%] and others. The appropriate one stage radical operations were applied to the all congenital cases with the result of 2.6% immediate postoperative hospital mortality rate. 4. Among the 130 acquired cases, there were 122 cases of valvular heart diseases, 6 of heart tumors [5 myxoma, one malignant histiocytoma], one of LA thrombus and one of annuloaortic ectasia. Cardiac tumors and LA thrombus were removed through the atrial septal approach. Bentall procedure was adopted to the annuloaortic ectasia case. AVR, MVR and TVA [DeVega procedure] were applied to 120 valve diseases, and there were also one of OMC and one of MVA[Jerome-Kay procedure]. 5. Among the 120 valve replacement cases, there were 87 of single valve replacement cases [AVR: 8, MVR: 79], 11 of double valve replacement [AVR+MVR: 11], 12 of MVR+TVR and 10 of MVR+AVR+TVA. The total number of implanted prosthetic valves were 141. In MVR, 45 of St. Jude Medical valves, 63 of Carpentier-Edward valves and 4 of Ionescu-Shiley valves were used. In AVR, 18 of St. Jude Medical valves and 11 of Carpentier-Edward valves were used. in MVR, 29mm and 31mm sized valves were used mostly and In AVR, 23mm sized valves were used mostly. 6. Postoperatively many kinds of complications were occurred. Among them, wound problems [30 cases], low output syndrome [29 cases], arrhythmia [20 cases], pleural effusion and pneumothorax [13 cases] were occurred frequently. The postoperative immediate hospital mortality was 3.0% in total [congenital 2.6%, acquired 4.6%].

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