• Journal of Chest Surgery
• /
• v.38 no.4 s.249
• /
• pp.271-276
• /
• 2005

We analysed differences in operative methods and postoperative outcome according to the severity of preoperative cyanosis in adult ToF (Tetralogy of Fallot) patients. Material and Method: From August 1989 to June 2001, thirty three adult patients, 18 females and 15 males, underwent total correction for ToF. Their age ranged from 15 years to 54 years (median: 34). Patients were divided into 2 groups by preoperative $SaO_2$ (arterial oxygen saturation): group I$(n=cyanotic,\;SaO_2\;\geq94\%)$ and group II $(acyanotic,\; SaO_2\geq95%)$. Preoperative median hemoglobin level was higher in group I compared to group II (17.5 g/dl vs 15 g/dl). Postoperative follow-up duration ranged from 1 to 94 months (670 patient-month, median: 14 months), and 63 two-dimensional echocardiographic examinations were done during this period. Result: There were no early or late mortality. With regard to RVOT (right ventricular outflow tract) reconstruction, trans-annular patch and RV-PA extracardiac conduit were used in 7 and 3 patients respectively, and all of them belonged to group I. In group I, cardiopulmonary bypass time, aortic cross-clamping time, ICU day, hospital day were significantly longer than in group II, and postoperative inotropic support was significantly greater than in group II. There was no ventricular arrhythmia in both groups, and one patient in group I suffered from atrial arrhythmia, which was resolved spontaneously after tricuspid and pulmonary valve replacement. During follow-up periods, functional class, residual RVOT stenosis and pulmonary regurgitation, tricuspid regurgitation, occurrence of ventricular and atrial arrhythmias were comparable between two groups. Conclusion: In adult ToF patients with severe preoperative cyanosis, more aggressive RVOT reconstruction and careful postoperative care are mandatory. However intermediate-term outcome of this group of patients is comparable to the patients with minimal or no preoperative cyanosis.

• Journal of Chest Surgery
• /
• v.42 no.3
• /
• pp.305-310
• /
• 2009

Background: The Ross procedure is known as a good surgical option for a young age group with aortic valve problems, but few reports on the Ross procedure are available in the Korean literature. This study is a review of our midterm results of 10 year experience with the pediatric Ross operation in Asan Medical Center. Material and Method: From March 1997 to October 2008, eighteen patients who were aged less than 16 years underwent the Ross procedure. There were 11 males and 7 females. The patients median age was 8.5 years (range: $0.5\sim14.0$). The aortic valve pathophysiology was 6 patients with aortic insufficiency, 4 patients with aortic stenosis, 7 patients with mixed aortic stenoinsufficiencey and 1 patient with infective endocarditis. The valve morphology was bicuspid in 11 and tricuspid in 7. All the patients were operated on with the root replacement technique. All the pumonic valves were replaced with an allograft except for one pericardial monocusp valve. The mean follow up duration was 52.8 months (range: 5.8$\sim$138.2 months). We reviewed the echocardiographic data with focusing on the, auto-graft dysfunction and reoperation. Result: There was no hospital mortality and late mortality. According to the last echocardiographic data, 2 autografts showed aortic regurgitation grade 2, 4 autografts showed aortic regurgitation grade 1 and the others were less than trivial. Reoperation of the pulmonic position conduit was performed 4 times in three patients. The rate of freedom from reoperation at 5 years was 72.2%. On the serial follow up, the Z-values of the aortic annulus/aortic sinus were changed from $1.6{\pm}1.7/0.9{\pm}1.7$ at preoperation to $1.8{\pm}1.6$(p=0.64)/$2.2{\pm}0.9$ (p=0.01) at the last follow-up. There was no significant relation between the growth of the neoaortic root and neoaortic insufficiency. Conclusion: Our midterm results of the Ross procedure in pediatric patients showed good autograft function and growth potential. Vet reoperation due to allograft dysfunction was a major concern.

• Journal of Chest Surgery
• /
• v.35 no.1
• /
• pp.36-42
• /
• 2002

Background: To evaluate the efficiency of surgical treatment in patients with cardiac valvular and arterial involvement of Behcet's syndrome. Material and Method: 12 patients underwent surgical treatment due to the valvular heart diseases and the various arterial diseases associated with Behest's syndrome over 7 years; 6 with valvular heart disease, 1 with annuloaortic ectasia, 1 with ascending aortic aneurysm, 4 with pseudoaneurysms in abdominal aorta(n=2), carotid artery(n=1), and popliteal artery(n=1). All 12 patients had received valvular replacement(n=6) and the artificial(n=5) or autologous(n=1) graft interposition. We followed the results of these surgical treatments. Result: Operations were technically successful in all 12 patients and peri-operative complication was not demonstrated. However, 10 patients had recurrences; 6 with valvular dehiscence, 3 with pseudoaneurysm at anastostomosis site, and 1 with aorto-duodenal fistula. The duration of recurrence was 1 to 55 months(mean: 15.7$\pm$ 16.2 months). 7 patients underwent the second operation and among them, 4 patients showed repeated recurrences. Overall, 5 patients died 2 to 25 months after the operation(mean: 13.6 months), because of the bleeding at the anastomosis site Five patients did not present recurrence after the first(n=2) or the second operation(n=3) and their follow up duration was 5 to 60 months(mean: 45.8$\pm$41.7 months). Five patients received immune-suppressive therapy after the first(n=2) and second operation(n=3). Three did not shown recurrence for the 13, 29 and 33 months. Conclusion: Post-operative prognosis of arterial manifestation of Behcet's syndrome was not encouraging and if possible, other treatment strategy should be considered.

• Journal of Chest Surgery
• /
• v.38 no.3 s.248
• /
• pp.221-228
• /
• 2005

Reduction aortoplasty has been advocated for dilatation of the ascending aorta associated with aortic valve disease in older, high-risk patients. We report our results with modification of reduction aortoplasty and aortic valve replacement. Material and Method: Between July 2001 and December 2002, 14 consecutive patients who underwent modification of reduction aortoplasty, suture plication technique without excision of the dilated aortic wall, were reviewed. The mean age was 63.7$\pm$6.7 (50 to 75) years. Ten patients had congenital bicuspid aortic valve, Twelve patients had severe aortic valve stenosis and 6 had regurgitation of grade III$\~$IV. The diameter of the ascending aorta was measured before and immediately after surgery and 6 and 12 months postoperatively using echocardiography or computed tomography. Follow-up was complete in an average of 14.7$\~$5.4 (7 to 24) months. Result: There were no early postoperative deaths and no bleeding complications. Reduction aortoplasty with suture plication technique decreased the diameter of ascending aorta from 49.4$\pm$3.5 mm preoperatively to 33.2$\pm$3.4 mm postoperatively (p <0.001). During follow-up, there were no late deaths and no aneurysm recurrence on the ascending aorta. Conclusion: Suture plication technique of reduction aortoplasty without excision of the dilated aortic wall offers good early and short-term results in older, high-risk patients with dilatation of the ascending aorta associated with aortic valve disease. Surgical long-term results of our technique should be evaluated in further studies.

• Journal of Intelligence and Information Systems
• /
• v.20 no.4
• /
• pp.121-139
• /
• 2014

Predicting corporate failure has been an important topic in accounting and finance. The costs associated with bankruptcy are high, so the accuracy of bankruptcy prediction is greatly important for financial institutions. Lots of researchers have dealt with the topic associated with bankruptcy prediction in the past three decades. The current research attempts to use ensemble models for improving the performance of bankruptcy prediction. Ensemble classification is to combine individually trained classifiers in order to gain more accurate prediction than individual models. Ensemble techniques are shown to be very useful for improving the generalization ability of the classifier. Bagging is the most commonly used methods for constructing ensemble classifiers. In bagging, the different training data subsets are randomly drawn with replacement from the original training dataset. Base classifiers are trained on the different bootstrap samples. Instance selection is to select critical instances while deleting and removing irrelevant and harmful instances from the original set. Instance selection and bagging are quite well known in data mining. However, few studies have dealt with the integration of instance selection and bagging. This study proposes an improved bagging ensemble based on instance selection using genetic algorithms (GA) for improving the performance of SVM. GA is an efficient optimization procedure based on the theory of natural selection and evolution. GA uses the idea of survival of the fittest by progressively accepting better solutions to the problems. GA searches by maintaining a population of solutions from which better solutions are created rather than making incremental changes to a single solution to the problem. The initial solution population is generated randomly and evolves into the next generation by genetic operators such as selection, crossover and mutation. The solutions coded by strings are evaluated by the fitness function. The proposed model consists of two phases: GA based Instance Selection and Instance based Bagging. In the first phase, GA is used to select optimal instance subset that is used as input data of bagging model. In this study, the chromosome is encoded as a form of binary string for the instance subset. In this phase, the population size was set to 100 while maximum number of generations was set to 150. We set the crossover rate and mutation rate to 0.7 and 0.1 respectively. We used the prediction accuracy of model as the fitness function of GA. SVM model is trained on training data set using the selected instance subset. The prediction accuracy of SVM model over test data set is used as fitness value in order to avoid overfitting. In the second phase, we used the optimal instance subset selected in the first phase as input data of bagging model. We used SVM model as base classifier for bagging ensemble. The majority voting scheme was used as a combining method in this study. This study applies the proposed model to the bankruptcy prediction problem using a real data set from Korean companies. The research data used in this study contains 1832 externally non-audited firms which filed for bankruptcy (916 cases) and non-bankruptcy (916 cases). Financial ratios categorized as stability, profitability, growth, activity and cash flow were investigated through literature review and basic statistical methods and we selected 8 financial ratios as the final input variables. We separated the whole data into three subsets as training, test and validation data set. In this study, we compared the proposed model with several comparative models including the simple individual SVM model, the simple bagging model and the instance selection based SVM model. The McNemar tests were used to examine whether the proposed model significantly outperforms the other models. The experimental results show that the proposed model outperforms the other models.

• Journal of Chest Surgery
• /
• v.37 no.6
• /
• pp.517-523
• /
• 2004

Background: The location of intimal tear can vary in type A acute aortic dissection. The aim of this study was to assess the operative result according to the intimal tear site. Material and Method: From January, 1995 to May, 2003, 18 patients underwent surgery for acute type A aortic dissection. The patients were classified according to the intimal tear site. In Group I (n=11), the intimal tear site was located within the ascending aorta, in Group II (n=7), the intimal tear site was located in the aortic arch, descending aorta, or intramural hematoma only. All clinical data were analyzed retrospectively. Result: In Group I, the operative time, cardiopulmonary bypass time, aorta cross clamp time and circulatory arrest time were 381.5$\pm$81.0 min, 223.5$\pm$42.5 min, 146.4$\pm$34.8 min and 36.5$\pm$17.4 min, respectively; and in group II, 461.7$\pm$54.0 min, 252.5$\pm$45.3 min, 162.5$\pm$45.3 min and 47.0$\pm$14.4 min respectively. All of those were greater in group II. The overall hospital mortality rate was 27.8% (5/18) and was significantly higher in Group II (57.1%)(p=0.003) compared to that in Group I (9.1%). The causes of death were hemorrhage (n=1) in group I and hemorrhage (n=2), multiple organ failure (n=1), and rupture of abdominal aorta (n=1) in group II. Conclusion: Surgical treatment of acute type A aortic dissection with intimal tear in the ascending aorta results in an acceptable mortality rate, but in patients with intimal tear in the aortic arch or descending aorta, the operative mortality still remains high when only ascending aorta replacement was performed. In these circumstances, in order to improve surgical results, efforts to include the intimal tear site in the operative procedure will be needed.

• Journal of Chest Surgery
• /
• v.39 no.12 s.269
• /
• pp.913-919
• /
• 2006

Background: Vasodilatory shock has been implicated in life-threatening complications after open heart surgery, where the systemic inflammatory reaction is attributed to the cardiopulmonary bypass(CPB). The secretion of arginine vasopressin(AVP) has been found to be defective in a variety of vasodilatory shock states and administration of AVP markedly improves vasomotor tone and blood pressure. So we reviewed our experience of AVP therapy in patients with vasodilatory shock following heart surgery using CPB. Material and Method: From January 2004 to July 2006, we reviewed the records of patients who received AVP therapy for vasodilatory shock following heart surgery using CPB. Vasodilatory shock was defined as a mean arterial pressure lower(MAP) than 70 mmHg, a cardiac index greater than 2.5 $L/min/m^2$, peripheral vascular resistance lower than 800 $dyn/s/cm^5$, and vasopressor requirements. The hemodynamic responses of patients who received AVP therapy for vasodilatory shock after cardiac surgery were analyzed retrospectively. Result: One hundred ninety nine open cardiac surgery patients were consecutively included in this study. Twenty two patients(11.1%) met criteria for vasodilatory shock. Despite the administration of high dose catecholamine vasopressor, all patients were hypotensive with a mean arterial pressure less than 70 mmHg. AVP therapy increased MAP from $53.3{\pm}7.4\;to\;82.0{\pm}12.0$ mmHg at 1 hour (p<0.001) and decreased other vasopressor requirements from $25{\pm}7\;to\;18{\pm}6$ at 1 hour(p<0.001) and individually maintained it for 12 hours. Conclusion: Our date suggest that AVP may be a safe and an effective vasopressor in patients with vasodilatory shock. In patients exhibiting vasodilatory shock after heart surgery, replacement of AVP increases blood pressure and reduces catecholamine vasopressor requirements.

• Journal of Chest Surgery
• /
• v.31 no.8
• /
• pp.739-748
• /
• 1998

Background: It has been well documented that transient occlusion of the coronary artery causes myocardial ischemia and finally cell death when ischemia is sustained for more than 20 minutes. Extensive studies have revealed that ischemic myocardium cannot recover without reperfusion by adequate restoration of blood flow, however, reperfusion can cause long-lasting cardiac dysfunction and aggravation of structural damage. The author therefore attempted to examine the effect of postischemic reperfusion on myocardial ultrastructure and to determine the rationales for recanalization therapy to salvage ischemic myocardium. Materials and methods: Young Holstein-Friesian cows(130∼140 Kg body weight; n=40) of both sexes, maintained with nutritionally balanced diet and under constant conditions, were used. The left anterior descending coronary artery(LAD) was occluded by ligation with 4-0 silk snare for 20 minutes and recanalized by release of the ligation under continuous intravenous drip anesthesia with sodium pentobarbital(0.15 mg/Kg/min). Drill biopsies of the risk area (antero-lateral wall) were performed at just on reperfusion(5 minutes), 1-, 2-, 3-, 6-, 12-hours after recanalization, and at 1-hour assist(only with mechanical respiration and fluid replacement) after 12-hour recanalization. The materials were subdivided into subepicardial and subendocardial tissues. Tissue samples were examined with a transmission electron microscope (Philips EM 300) at the accelerating voltage of 60 KeV. Results: After a 20-minute ligation of the LAD, myocytes showed slight to moderate degree of ultrastructural changes including subsarcolemmal bleb formation, loss of nuclear matrix, clumping of chromatin and margination, mitochondrial destruction, and contracture of sarcomeres. However, microvascular structures were relatively well preserved. After 1-hour reperfusion, nuclear and mitochondrial matrices reappeared and intravascular plugging by polymorphonuclear leukocytes or platelets was observed. However, nucleoli and intramitochondrial granules reappeared within 3 hours of reperfusion and a large number of myocytes were recovered progressively within 6 hours of reperfusion. Recovery was apparent in the subepicardial myocytes and there were no distinct changes in the ultrastructure except narrowed lumen of the microvessels in the later period of reperfusion. Conclusions: It is likely that the ischemic myocardium could not be salvaged without adequate restoration of coronary flow and that the microvasculature is more resistant to reversible period of ischemia than subendocardium and subepicardium. Therefore, thrombolysis and/or angioplasty may be a rational method of therapy for coronarogenic myocardial ischemia. However, it may take a relatively longer period of time to recover from ischemic insult and reperfusion injury should be considered.

• Journal of Chest Surgery
• /
• v.42 no.2
• /
• pp.175-183
• /
• 2009

Background: Mitral valve abnormalities in the pediatric population are rare. Mitral valve replacement or pediatric mitral lesions can cause problems such as a lack of growth potential. There re only limited experiences with mitral valve repair at any institution, so the purpose of his study is to evaluate the outcomes of mitral valve repair n pediatric patients. Material and Method: Sixty-four consecutive children (28 males and 36 females) with a mean age of $5.5{\pm}4.7$ years underwent mitral valve repair for treating their congenital mitral valve disease between January 1996 and December 2005. The patients were divided into two groups: group 1 (34 patients (53.1%)) had isolated disease (mitral anomaly with or without trial septal defect or patent ductus arteriosus) and group 2 (30 patients (46.9%)) had complex disease (mitral anomaly with concurrent intracardiac disease, except atrioventricular septal defect). Result: The overall in-hospital mortality was 6.3%; group 1 had 5.9% mortality and group 2 had 10.0% mortality. The postoperative morbidity was 18.8%; group 1 and 2 had 14.7% and 23.3% postoperative morbidity, respectively, and there as no significant difference among the groups. The median follow-up was 4.6 years range: $0.5{\sim}12.2$ years). The 10-year survival rate was 95.3%. The 10-year freedom from re-operation rate was 76.1% with 10 re-operations. The majority of the functional classifications were annular dilatation and leaflet prolapse. A mean of $2.1{\pm}1.1$ procedures per patient were performed. The echocardiography that was done at the immediate postoperative period showed a significant improvement in the mitral valve function. The follow-up echocardiographic results were significantly improved. However, mitral stenosis newly developed over time, and there ere significant differences according to the repair strategies. Conclusion: The patients who underwent mitral valve repair for congenital mitral anomalies showed good results. The follow-up echocardiography revealed satisfactory short-term and long-term results. Close follow-up is necessary to detect the development of postoperative mitral stenosis or regurgitation.

• Development and Reproduction
• /
• v.12 no.1
• /
• pp.77-86
• /
• 2008

This study was carried out to investigate the effect of leukemia inhibitory factor (LIF) on the derivation of mouse ES cells from isolated blastomeres. Two-cell stage mouse embryos were obtained from superovulated BDF1 female mice. Collected embryos were cultured to blastocyst stage in culture medium supplemented with 0, 1,000, 2,500 or 5,000 U/mL of LIF. Cultured blastocysts were examined by counting the number of cells in the inner cell mass (ICM) and trophectoderm (TE) using differential staining method. When 2-cell embryos were cultured with 2,500 U/ml of LIF, the cell numbers of ICM significantly increased in comparing with those of the control($21.0{\pm}4.0$ vs. $15.9{\pm}5.0$, P<0.01) and 1,000 U/mL of LIF-containing group ($21.0{\pm}4.0$ vs. $16.6{\pm}4.9$, P<0.05). We used an ES cell establishment medium with 20% Knockout Serum Replacement and 0.01 mg/mL ACTH instead of fetal bovine serum. Establishing efficacy of ES cell lines were the highest in 2,500 U/mL of LIF-containing group as 36.7% (11/30). This culture medium was applied to the culture of isolated blastomeres and to derivate ES cell lines. Three ES cell lines (21.4%) from isolated blastomeres of 2-cell stage embryos were established. In further experiments, we could establish one ES cell line (4.0%) from single blastomere of 4-cell stage embryo. The subcultured ES cells and their embryoid bodies were characterized by analyzing gene expression for undifferentiation and differentiation marker gene using immunocytochemistry and RT-PCR. In conclusion, LIF supplementation in culture medium could increase the cell number in ICM of blastocysts and support derivation of ES cell lines from isolated blastomeres.