• 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.

• Journal of Chest Surgery
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• v.29 no.2
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• pp.164-170
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• 1996

From January 1986 to June 1993, 12 patients Aad required reoperation: 9 had undergone mitral and 3 aortic valve replacement. Five were male and 7 female, and ages ranged from 29 to 61 years. Replacement of the prosthetic heart valve was performed at a mean interval of 98 $\pm$ 1 months after the Hrst operation. In aortic valve replacement patients the mean interval was 115 $\pm$ 2 months and in mitral valve replacement patients 98 $\pm$ 4 months. Primary tissue failure was the most frequent reason of replacement (10 patients) followed by valve thrombosis (1 patient) and prophylactic replacement (1 patient) in order. The most pronounced pathology of the failed prosthetic heart valves seen in the primary tissue failure group was calcification, perforation, shrinkage and tearing of the cusps. There was one early operative death (8.3%) due to intractable low cardiac output and acute renal failure. Eleven early survivors had successful operative results and there was no late death.

• Journal of Chest Surgery
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• v.24 no.2
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• pp.171-181
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• 1991

Result of St. Jude Medical valve replacement are presented in 106 patients who underwent operation from January 1985 through July 1989. The patient were 52 males and 56 females. Total 136 of St. Jude Medical valves were implanted; 91 in mitral position, 45 in aortic position. The hospital mortality rate was 5.7%o[6 patients] and the late mortality rate was 2.0%[2 patients]. The causes of death were low cardiac output in 5, iatrogenic right ventricular rupture in 1, heart failure in 1, ventricular arrhythmia in l. And, the causes of valve related complication were anticoagulant related hemorrhage in 5 patients[0.03% /patient-year] and thromboembolism[0.01% /patient-year] in 2 patients. In conclusion, the performance of the St. Jude Medical valve compare most favorably with other artificial valves. But it remains still hazards of mechanical prosthesis such as thromboembolism and anticoagulant related hemorrhage.

• Journal of Chest Surgery
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• v.32 no.11
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• pp.1023-1030
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• 1999

This is a retrospective study of 42 pregnancies from 33 women with prosthetic heart valves who were on anticoagulation regimen prior to or during their pregnancy. Material and Method: Of the 17 women with bioprosthesis, 15 had 21 pregnancies following cessation of the anticoagulation therapy which resulted in the delivery of 20 healthy babies and 1 abortion. Remaining 2 had 3 pregnancies maintained with heparin, resulting in 2 healthy babies and 1 spontaneous abortion. Result: Among 16 women with mechanical heart valves, there were 7 pregnancies during which warfarin was used and this was associated with 4 fetal wastages(2 therapeutic abortion, 1 spontaneous abortion and 1 stillbirth with cerebral hemorrhage). However, in pregnancies where heparin was used, there was no fetal wastage. A patient who did not take anticoagulant for the first trimester and took warfarin for the remaining period and a patient who did not take anticoagulant during pregnancy delivered normal babies. There was an other fetal wastage in a patient on anti-platelet therapy for the first trimester and warfarin therapy for the remaining periods. There was 1 minor petechial complication in a heparin administered group. Conclusion: The study indicates that woman with bioprosthetic heart valves can go through pregnancy without undue risks or complications. On the other hand, the use of warfarin during pregnancy in women with mechanical heart valves, was shown to be associated with unacceptable high risk for the fetus. However, in the same group of women, judicious use of heparin during pregnancy was accompanied by a much reduced risk. The safety and adequate therapeutic range of heparin usage under such circumstances are subject to further studies.

• Journal of Chest Surgery
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• v.28 no.9
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• pp.822-828
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• 1995

This paper reports 15 native valve endocarditis cases had surgical operation in the past 10 years at the department of Cardiovascular and Thoracic Surgery, Chonbuk National University Hospital. In this study, 10 cases out of 15 were in class I or II by the New York Heart Association functional classification. None of the cases had a history of taking addictive drugs. Five cases were congenital heart disease, three cases were rheumatic heart disease and two cases were degenerative heart disease. Thus 10 cases had the underlying disease. All cases had antibiotics treatment for 3 to 6 weeks before operation. In the culture test, only four cases were positive in the blood culture and one case was positive in the excised valve culture. Organisms on blood and valve culture were Streptococcus epidermis, Streptococcus viridans, Staphylococcus aureus and Staphylococcus epidermidis. In the 10 cases without ventricular septal defect, the aortic valve was involved in four, mitral in four, both in two and involved valves in the 5 cases with ventricular septal defect were tricuspid in three, pulmonic in two. Eight cases had operation because they showed moderate congestive heart failure due to valvular insufficiency and vegetation with or without embolism. Seven cases had operation because they showed persistent or progressive congestive heart failure and/or uncontrolled infection. Five cases with ventricular septal defect underwent the closure of ventricular septal defect, vegetectomy and leaflet excision of the affected valves without valve replacement. In the cases without ventricular septal defect, the affected valves were replaced with St. Jude mechanical prosthesis. Postoperative complications were recurrent endocarditis in two, embolism in one, allergic vasculitis in two, spleen rupture in one and postpericardiotomy syndrome in one. At the first postoperative day, one case died of cerebral embolism. At the 11th postoperative month, one case died of recurrent endocarditis and paravalvular leakage in spite of a couple of aortic valve replacement. In the survived cases[13 cases in this study , all cases but one became class I or II by the New York Heart Association functional classification.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.5
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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.

• Journal of Chest Surgery
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• v.30 no.3
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• pp.293-299
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• 1997

With the introduction of new cardiac prosthesis, it behooves surgeons and cardiologists to monitor its performance carefully. ATS (Advancing The Standard) prosthetic valve has been used first in Guro hospital in Korea, since August 1994. Between August 1994 and July 1995, 21 patients received 28 ATS prosthesis(9 aortic, 19 mitral).19mi1ra1 valves were implanted through the "Extended Transseptal Approach" 10 were ma e and 11 were female, ranging from 20 to 54 years of age(Mean age : 37 years). The follow up period 126 patient-months(mean 6.1 months), varied from 1 month to 12 months. NYHA functional class was improved significantly, from $2.9\pm0.7$ preoperatively to $1.4\pm0.5$ postoperatively. Ejection fraction was also improved from $55.5\pm6.1%$ preoperatively to 59.8 $\pm7.4%$ postoperatively. Lactic dehydrogenase(LDH) was used as an indicator of hemolysis. The value of LDH changed from 483.3 $\pm$ 162 lUlL preoperatively to $527\pm274$ lUff postoperatively with no clinical significailce. Valve related complications, such as thromboembolism, valve thrombosis, anticoagulant related hemorrhage and prosthetic valve endocarditis did not develop except one anticoagulant related intracranial hemorrhage. There were no mortalities. This experience encourages us to continue using the ATS prosthetic valve, and this study will help those patients who need to have their heart valves replaced. replaced.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.2
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• pp.443-450
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• 1995

An analysis of the dynamics of a mechanical monoleaflet heart valve prosthesis in the closing phase is presented. Employing the moment equilibrium principles on the occluder motion and the squeeze film dynamics of the fluid between the occluder and the guiding strut at the instant of impact, the velocity of the occluder tip and the impact force were computed. The dynamics of fluid being squeezed between the occluder and the guiding struts is accounted for by Reynold's equation. The effect of the fluid being squeezed between the occluder and the guiding strut was to reduce the velocity of the occluder tip at the instant of valve closure as well as dampen the fluttering of the occluder before coming to rest in the fully closed position. The squeeze film fluid pressure changed rapidly from a high positive value to a relatively large negative value in less than 1 msec. The results of this study may be extended for the analysis of cavitation inception, mechanical stresses on the formed elements and valve components as well as to estimate the endurance limits of the prosthetic valves.

• 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.

• Proceedings of the KOSOMBE Conference
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• v.1993 no.11
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• pp.81-84
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• 1993

Artificial Heart Valve is the one of the most important artificial organ which has been implanted to many patients. The most important problems related to the artificial heart valve prosthesis are thrombosis and hemolysis. Usual method to test against this problem in vivo experiment, which is complex and hard work. Nowadays the request for In vitro Artificial Heart Valve testing system is increasing. Several papers has announced us flow pattern of Artificial Heart Valve is highly correlated with thrombosis and hemolysis. They usually gel flow pattern by LDA, it is also hard work and has narrow measuring region. In this reason we have determined to develop PTV(Particle Tracking Velocimetry). By using High-speed camera and image processing technique, flow pattern could be relatively easily obtained. Parachute and Bileaflet Artificial Heart Valve designed by SNU were testified.