• Journal of Chest Surgery
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• v.9 no.2
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• pp.207-214
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• 1976

Operations for cardiac valvular disease has been progressed in various ways. Since 1949 when Lord Russel operated mitral stenosis by closed technique at Johns Hopkins Hospital then much progress has been achieved and that nowadays severely diseased cardiac valve has been replaced by prosthetic valve, which is almost ideal in hemodynamic aspect, but still it has many problems such as thromboembolism, destruction of red blood cell, pressure gradient, and disturbance of left ventricular function, so in case of delicate situations, valve replacement should be decided carefully. Besides prosthetic valve, there are some kinds of reconstructive procedures and these have been resulted in better prognosis than prosthetic valve replacement in selected cases. So, authors have reviewed 61 Cases of cardiac patients who have been operated reconstructive valvular surgery by cardiopulmonary bypass, at Yonsei University, from Jan. 1963 to Mar. 1976. Out of 61 cases, 9 patients were replaced by prosthetic valve and rest of the patients were operated upon in various reconstructive procedures such as commissurotomy, valvotomy, valvuloplasty, and annuloplasty. Twenty cases of congenital heart diseases with valvular lesion, which had been operated for valvular lesion were also included in this statistics. Out of 9 cases of prosthetic valvular replacement five cases of prosthetic valvular replacement was done combined with other reconstructive procedures after attempted valvuloplasty. Comparative prognosis of both procedures are somewhat variable by reporters, average 19% of mortality after reconstructive surgery and 38% of mortality after prosthetic valve replacement in long term results. Most common cause of death in postoperative period was low output syndrome in both cases. It seems that good preoperative evaluation and proper reconstructive surgery will afford good prognosis in selected cardiac valvular diseased patient.

• Journal of Chest Surgery
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• v.32 no.11
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• pp.1017-1022
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• 1999

Background: An increasing number of elderly are referred for open heart surgeries(OHS). These patients are assumed to have significantly increased morbidity and mortality because of compromised functional reserves in their vital organs. We reviewed the results of OHS patients who were 70 years old or older. Material and Method: Thirty six consecutive septuagenarians underwent OHS from 1995 to 1997. Operations were coronary artery bypass grafting(CABG) in 26 including 3 left main surgical angioplasty, valve replacement in 7, MVR+CABG in 2, and ASD closure+TAP in 1. Statistical tests were carried out to compare survivor group with nonsurvivor group in respect to risk factors including NYHA functional class, LVEF, emergent operation, IABP support, CPB/ACC time, ventilator time cardiac index, ICU stay and hospital stay for operative mortality. Result: Operative mortality rate and postoperative complication were 16%(6/36) and 50%(18/36). One-year and 3-year actuarial survival rates were 76%. Nine patients(25%) had major complications including third-degree A-V block(2), respiratory failure(1), stroke(3), renal failure requiring dialysis(3) and postoperative hemorrhage(2). The causes of death were pneumonia(1), bleeding(1), acute renal failure(1), low cardiac output(1), third-degree A-V block(1), and ventricular tachycardia(1). The univariate analysis of mortality shows that NYHA class IV, LVEF<40%, lesser values for C.I, and longer time for ventilatory support were associated with the risk factors(p value=0.03, 0.001, 0.007, and 0.014). The emergent operation, CPB/ACC time, IABP support, ICU stay and hospital stay were not significant. Conclusion: We conclude that cardiac operation can be performed in septuagenarians with acceptable outcomes when done in patients with normal to moderately depressed left ventricular function and adequate functional reserves in their vital organs.

• Journal of Chest Surgery
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• v.48 no.6
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• pp.407-410
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• 2015

A two-month-old infant presented with coarctation of the aorta, severe left ventricular dysfunction, and moderate to severe mitral regurgitation. Through median sternotomy, the aortic arch was repaired under cardiopulmonary bypass and regional cerebral perfusion. The patient was postoperatively supported with a left ventricular assist device for five days. Left ventricular function gradually improved, eventually recovering with the concomitant regression of mitral regurgitation. Prompt surgical repair of coarctation of the aorta is indicated for patients with severe left ventricular dysfunction. A central approach for surgical repair with a back-up left ventricular assist device is a safe and effective treatment strategy for these patients.

• Journal of Chest Surgery
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• v.51 no.1
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• pp.1-7
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• 2018

Background: Sutureless aortic valve replacement (SU-AVR) has been developed as an alternative surgical treatment for patients with symptomatic severe aortic stenosis (AS). The aim of this study was to evaluate the clinical outcomes of SU-AVR through an assessment of hemodynamic performance and safety. Methods: From December 2014 to June 2016, a total of 12 consecutive patients with severe AS underwent SU-AVR. The endpoints were overall survival and valve-related complications (paravalvular leakage, valve thrombosis, migration, endocarditis, and permanent pacemaker implantation). The mean follow-up duration was $18.1{\pm}8.6months$. Results: The mean age of the patients was $77.1{\pm}5.8years$ and their mean Society of Thoracic Surgeons score was $9.2{\pm}17.7$. The mean cardiopulmonary bypass and aortic cross-clamp times were $94.5{\pm}37.3$ minutes and $54.9{\pm}12.5minutes$, respectively. Follow-up echocardiography showed good prosthesis function with low transvalvular pressure gradients (mean, $13.9{\pm}8.6mm\;Hg$ and peak, $27.2{\pm}15.0mm\;Hg$) at a mean of $9.9{\pm}4.2months$. No cases of primary paravalvular leakage, valve thrombosis, migration, or endocarditis were reported. A new permanent pacemaker was implanted in 1 patient (8.3%). The 1-year overall survival rate was $83.3%{\pm}10.8%$. Conclusion: Our initial experience with SU-AVR demonstrated excellent early clinical outcomes with good hemodynamic results. However, there was a high incidence of permanent pacemaker implantation compared to the rate for conventional AVR, which is a problem that should be solved.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.8
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• pp.33-41
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• 2007

The IEEE 802.11 DCF channel access function allows single transmission inside two-hop network in order to avoid collisions and eliminate the hidden and exposed terminal problems. Singular transmission capability causes data frames waiting for the entire roundtrip time in the transmitter neighborhood, and results in increased frame latency and lower network throughput. Real-time and pervasive applications are severely affected for the lower medium utilization; especially with high network traffic. This work proposes a new scheme with the help of Frame Aggregation technique in IEEE802.11n and overcomes the single transmission barrier maintaining the basic DCF functionality. Proposed scheme allows parallel transmissions in non-interfering synchronized slots. Parallel transmissions bypass the conventional physical carrier sense and random Backoff time for several cases and reduce the frame latency and increase the medium utilization and network capacity.

• Journal of Chest Surgery
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• v.43 no.2
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• pp.164-167
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• 2010

Extracorporeal membrane oxygenation (ECMO) during acute respiratory failure due to any cause aids in the recovery of respiratory function. The use of ECMO for acute respiratory failure due to near drowning was reported to be a successful therapeutic option in those patients who do not respond to optimal conventional therapies. We performed veno-venous ECMO for 2 acute respiratory failures due to near-drownings. All cannulations were performed percutaneously via both femoral veins. The 2 patients were successfully weaned off ECMO, but one patient experienced diffuse hypoxic brain damage and a subarachnoid hemorrhage.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.3
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• pp.321-325
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• 2008

Void areas(holes) as an inevitable phenomenon exist in geographic routing of wireless sensor networks, because the unpredictable and harsh nature application environment or uneven energy consumption. Most of the existing schemes for the issue tend to construct a static detour path to bypass a hole. The static detour path may lead to uneven energy consumption of the nodes on the perimeter of the hole; thus it may enlarge the hole. At the same time, traffic would concentrate on the peripheral node of the hole; thus the nodes on the perimeter of the hole tend to be depleted quietly. In previous work, we have proposed a hole geometric model to reduce the energy consumption and packet collisions of the nodes on the hole boundary. This scheme, however, still has the static detour path problem. Therefore, we extend the previous work by constructing a dynamic detour path hole geometric model for wireless sensor networks in this paper. The location of hole detour anchors is dynamically shifted according to Gaussian function, just generating dynamic hole detour paths.

• Journal of Chest Surgery
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• v.27 no.12
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• pp.989-994
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• 1994

Between January 1986 and August 1993, 11 patients underwent surgical repair of ventricular septal defect [VSD] complicated with myocardial infarction. The ages of patients were ranged from 22 years to 83 years with a mean of 64 years. There were 8 male and 3 female patients. The preoperative cineangiograms of all patients were reviewed to measure both ventricular function and to evaluate coronary artery disease. The mean time interval between occurance of VSD and operation was 13 days. The operations were performed as soon as possible if there were hemodynamic derangement. Postmyocardial infarction VSD were repaired simultaneuously with coronary artery bypass graft in 3 patients, repaired with left ventricular aneurysmectomy in 6 patients, with left ventricular thrombectomy in 1 patient and with mitral valve chordae repair in 1 patient. There was no early death [within 30 days]. There were 6 postoperative complications; one with perioperative myocardial infarction, two with recurred VSD on postoperative 1 and 6 days respectively, two with lower leg embolism associated with intraaortic balloon pump insertion, one with wound infection. Of the complicated patients, 1 patient with lower leg embolism performed left above ankle amputation. Among two patients with recurred ventricular septal defect, one patient is doing well without problem. On follow up echocardiogram, the residual VSD was occluded completely. However another patient was with recurred VSD died 3 months after the operation because of congestive heart failure. Of the long term survivors, all patients are in NEW YORK Heart Association functional Class I or II. Although number of patients were small, our results of surgical closure of postmyocardial infarction VSD were favored to the others. Moreover, seven patients with preoperative cardiogenic shock among 11 were performed early operation after diagnosis of ventricular septal rupture. All of the patients were survived and doing well during the follow up period. Therefore early diagnosis with aggressive preoperative care with intraaortic balloon pumping and early operation seems to be very important for prevention of deterioration of vital organ.

• Nuclear Engineering and Technology
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• v.27 no.3
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• pp.317-326
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• 1995

The oater level control system of the steam generator in a pressurized water reactor and its control Problems are analysed. In this work a stable control strategy Particularly during low Power operation based on the fuzzy control method is studied. The control strategy employs substitutional information using the bypass valve opening instead of incorrectly measured signal at the low How rate as the fuzzy variable of the flow rate during low power operation, and includes the flexible scale adjusting method for fast response at a large transient. A self-tuning algorithm based on the control performance and the descent method is also suggested for tuning the membership function scale. It gives a practical way to tune the controller under real operation. Simulation was carried out on the Compact Nuclear Simulator set up at Korea Atomic Energy Research Institute and its result showed the good performance of the controller and effectiveness of its tuning.

• IMMUNE NETWORK
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• v.13 no.2
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• pp.63-69
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• 2013

IL-12 is a secretory heterodimeric cytokine composed of p35 and p40 subunits. IL-12 p35 and p40 subunits are sometimes produced as monomers or homodimers. IL-12 is also produced as a membrane-bound form in some cases. In this study, we hypothesized that the membrane-bound form of IL-12 subunits may function as a costimulatory signal for selective activation of TAA-specific CTL through direct priming without involving antigen presenting cells and helper T cells. MethA fibrosarcoma cells were transfected with expression vectors of membrane-bound form of IL-12p35 (mbIL-12p35) or IL-12p40 subunit (mbIL-12p40) and were selected under G418-containing medium. The tumor cell clones were analyzed for the expression of mbIL-12p35 or p40 subunit and for their stimulatory effects on macrophages. The responsible T-cell subpopulation for antitumor activity of mbIL-12p35 expressing tumor clone was also analyzed in T cell subset-depleted mice. Expression of transfected membranebound form of IL-12 subunits was stable during more than 3 months of in vitro culture, and the chimeric molecules were not released into culture supernatants. Neither the mbIL-12p35-expressing tumor clones nor mbIL-12p40-expressing tumor clones activated macrophages to secrete TNF-${\alpha}$. Growth of mbIL-12p35-expressing tumor clones was more accelerated in the $CD8^+$ T cell-depleted mice than in $CD4^+$ T cell-depleted or normal mice. These results suggest that $CD8^+$ T cells could be responsible for the rejection of mbIL-12p35-expressing tumor clone, which may bypass activation of antigen presenting cells and $CD4^+$ helper T cells.