• Journal of Biomedical Engineering Research
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• v.19 no.3
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• pp.291-296
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• 1998

A new mechanical heart valve prosthesis has been designed appling systematic design methodology. The function of the heart valve was defined, and search for design variation has been carried out according to the functional structure, Optimal model among the various variations was determined in view of the design specificationn. Proto type valve was fabricated and test has been carried out using a mock circulation system. It has been observed that the pressure profile, cardiac output and behavior characteristics are generally satisfactory.

• Journal of Chest Surgery
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• v.31 no.12
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• pp.1165-1171
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• 1998

Background: All currently available mechanical and bioprosthetic valves are associated with various types of deterioration leading to dysfunction and/or valvular complications. Reoperation on prosthetic heart valves is increasingly under consideration for both clinical and prophylactic indications. This review was conducted to determine the factors affecting the risk of reoperation for prosthetic valve replacement. Material and method: From January 1985 to July 1996, 124 patients underwent reoperation on prosthetic heart valves, and 3 patients had a second valve reoperation. The causes of reoperation were prosthetic valve failure(96 cases, 77.4%), prosthetic valve thrombosis(16 cases, 12.9%), prosthetic valve endocarditis(7 cases, 5.6%) and paravalvular leak(5 cases, 4.1%). This article is based on the analysis of the experience with particular emphasis on the preoperative risks affecting the outcome of the reoperation. Result: Overall hospital mortality rate was 8.9%(11/124). Low cardiac output was the most common cause of death(70.6%). Left ventricular systolic dimension(p=0.001), New York Heart Association functional class IV(p=0.003) and serum creatinine level(p=0.007) were the independent risk factors, but age, sex and cardiothoracic ratio did not have any influence on the operative mortality. Follow-up period was ranged from 3 to 141 months (mean, 50.6 months). A late mortality rate was 1.8%. Conclusion: The surgical risk of reoperation on heart valve prostheses in the advanced NYHA class patients is higher, therefore reoperation is recommended before the hemodynamic impairment become severe.

• Proceedings of the KTCVS Conference
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• 1995.10a
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• pp.48-48
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• 1995

• Journal of Chest Surgery
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• v.36 no.5
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• pp.316-320
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• 2003

Background: The detection of circulating microemboli by transcranial Doppler ultrasonography (TCD) has the potential to select the patients with high risk for future symptomatic brain embolism. We prospectively evaluated the positive rate and the frequency of microembolic signals (MES) before and after the heart valve surgery (HVS). Material and Method: Fifty in-patients with heart valve disease were enrolled in this study. Patients with history of previous stroke or heart valve surgery were excluded. Two unilateral TCD monitoring sessions were peformed from middle cerebral artery for 1-hour, before and after HVS. Result: Mechanical Heart valves were implanted in 28 patients, tissue valves were implanted in 10 patients, and remaining 12 patients received mitral valve repair. Positive rate of MES was significantly increased after HVS (50%), compared to that of before HVS (8%, p=0.00). There was no relation between MES after HVS and intensity of anticoagulation, cardiac rhythm, patients' age, and history of hypertension. The positive rate of MES after implantation of mechanical heart valve (71.4%) was significantly higher than those after implantation of tissue valve or mitral valve plasty (p=0.002). Conclusion: Positive rate of MES was increased significantly after the implantation of HVS. The changes of MES in those with mechanical prosthesis may be related to the increased risk or embolism after Hvs.

• 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.

• Proceedings of the KTCVS Conference
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• 1998.10a
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• pp.57-57
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• 1998

• Journal of Chest Surgery
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• v.37 no.1
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• pp.50-55
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• 2004

Background: Transcranial Doppler ultrasonography (TCD) can detect microembolic signals (MES) in the patients with a potential embolic source. Clinical significance of MES has not been demonstrated in patients with prosthetic mechanical heart valves. We studied the correlation between cerebral thromboemoblic events after the mechanical heart valve surgery (MHVS) and residual MES during TCD monitoring with 100% oxygen inhalation in patients with mechanical heart valves. Material and Method: Twenty patients with previous cerebral thromboemoblic events after MHVS and a sex- and age-matched control group (n=30) were studied. TCD monitoring was performed from unilateral middle cerebral artery. After baseline monitoring for 20 minutes, 61 of oxygen was inspired for 40 minutes. Result: The site of valve and the duration after MHVS of the patients did not differ from those of controls. During baseline monitoring, there was no significant difference in MES prevalence or counts compared to controls. During oxygen inhalation, patients showed a higher MES prevalence (55%, 27.6%, p=0.045) and a more frequent MES counts (p=0.027) compared to controls. Conclusion: TCD monitoring with oxygen inhalation may be useful to differentiate clinically significant MES in patients with mechanical heart valve.

• Proceedings of the KTCVS Conference
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• 1998.10a
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• pp.21-21
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• 1998

• Journal of Biomedical Engineering Research
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• v.21 no.5
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• pp.505-512
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• 2000

기계식 인공심장판막을 통한 혈액의 유동과 이 유동에 관련된 판첨의 거동특성을 수치해석기법을 이용하여 연구하였다. 혈액은 맥동류, 층류, 비압축성 유동으로 가정하였으며 유체-고체의 상호작용을 고려하기 위하여 혈액의 유동방정식과 고체의 운동방정식이 동시에 계산되었다. 심실과 대동맥에서의 압력파형을 경계조건으로 사용하였다. 연구의 결과로서 혈액유동과 판첨의 거동이 예측되었으며, 판막을 통한 3개의 제트가 발견되었으며 vortex가 판첨의 끝단에서 발생하여 하부로 흘러가는 것이 관찰되었다. 판첨의 닫힘 거동은 열림 거동에 비하여 2배정도 빠르게 진행되었으며 sinus에서 2개의 큰 vortex가 관찰되었다. 유체-고체 상호작용을 고려하는 본 연구방법은 향후 판막의 연구와 개발에 매우 유용할 것으로 판단된다.

• Journal of Chest Surgery
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• v.37 no.4
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• pp.373-375
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• 2004

Edwards Duromedics Valve has been suspended from the market since May 1988 due to the frequent reports of leaflet escape. There were 2 case-reports of leaflet escapes in this country. We report a case of leaflet escape in an Edwards Duromedics bileaflet valve, in the mitral position.