• Journal of Chest Surgery
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• v.30 no.2
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• pp.125-130
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• 1997

Separating the patient from hypothermic cardiopulmonary bypass(CPB) before achieving adequate rewarming often results in afterdrop, which can predispose to electrolyte disturbances, arrhythmia, hemodynamic alterations, and shivering-induced increase of oxygen consumption. In an attempt to find an adequate end point temperature of rewarming after hypothermic CPB, 50 pediatric cardiac surgical patients were r ndomly assigned for end point temperature of rewarming of 35.5$^{\circ}C$ (Group 1) or 37t (Group 2), rectal temperature. Thereafter the rectal temperature was measured half, one, four, eight, and 16 hour after arrival to the intensive care unit(ICU), with heart rate and blood pressure. Additionally the rectal temperature was compared with esophageal temperature during CPB, and axillary temperature luring stay in the ICU. Nonpulsatile perfusion with a roller pump was used in all patients and a membrane or bubble oxygenator was used for oxygenation. Both groups were comparable with respect to age, sex, body surface area, total bypass time, and rewarming time. There was no afterdrop in both groups, and there were no statistical differences in the rectal temperatures between two groups. There were also no statistical dilyerences with respect to the heart rate and blood pressure between two groups. At the end of rewarming the esophageal temperature was higher than the rectal temperature. The axil ary temperature measured in ICU was always lower than the rectal temperature. No shivering was noted in all patients. In conclusion, with restoration of rectal temperature above 35.5$^{\circ}C$ at the end of CPB in pediatric patients, we did not observe an afterdrop.

• Journal of Chest Surgery
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• v.30 no.3
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• pp.287-292
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• 1997

.Itrial fibrillation is one of the most common cardiac arrhythmias requiring treatment. About 60% of patients with mitral valvular disease have atrial fibrillation and one third of patients with atrial fibrillation may have the past history of thromboembolic events. Between April 1994 and June 1995, 20 patients with organic heart diseases combined with atrial fibrillation underwent open heart surgery including Cox-maze 111 procedure. There were 6 men and 14 women with an average age of 48 years (range, 31 to 66 years). Nineteen patients had valvular heart diseases and 1 ventricular septal defEct (VSD). Mean duration of atrial fibrillation was 36 months (:42 months) (range, 1 to 132 months). T e past medical history of thromboembolic events was positive in 7 patients (35%) and left atrial thrombus was detected in 9 patients (45%). The concomitant procedures were mitral valve replacement (MVR) and aortic valve replacement (AVR) in 5 patients, MVR in 4, MVd and tricuspid annuloplasty(TAP) in 4, mitral valvuloplasty(Mln) in 3, Mln and Tln in 1, MIW and coronary artery bypass surgery in 1, AVR in 1, and patch closure of VSD in 1. Mean aortic cross-clamping time was 175 minutes (range, 116 to 270 minutes). Atrial fibrillation recurred in 16 patients (80%) during the early postoperative period, but, recurrent atrial fibrillation was converted to regular rhythm at postoperative forty-first day in average. There was no early or late death in this series of 20 patients and postoperative complications were inappropriate tachycardia in 5 patients (25%), low cardiac output syndrome in 3 (15%), aggravated hemiplegic in 1, and acute renal failure in 1. Mean follow-up interval of patient was 16.5 months (range, 10.5 to 24 months) and all patients are currently in regular rhythm. Seventeen patients (85%) are in sinus rhythm and 3 (15%) in junctional rhythm. Right atrial contraction was detected in 95% of patients and left atrial contraction in 63% on postoperative transthoracic echocardiogram. The surgical treatment of atrial fibrillation concomitant with open heart surgery is warranted in the recent clinical setting of improved myocardial protection technique, considering the untoward side-effects of atrial fibrillation.

• Journal of Chest Surgery
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• v.41 no.5
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• pp.568-572
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• 2008

Background: Minimally invasive surgery is currently popular, but this has been applied very sparingly to cardiac surgery because of some limitations. Our study evaluated the safety and efficacy of atrial septal defect (ASD) closure through a video-assisted mini-thoracotomy. Material and Method: Fifteen patients were analyzed. Their mean age was $31{\pm}6$ years. The mean ASD size was $24{\pm}5mm$ and there were 3 cases of significant tricuspid regurgitation. The working window was made through the right 4th intercostal space via a $4{\sim}5cm$ inframammary skin incision, CPB was conducted with performing peripheral cannulation. After cardioplegic arrest, the ASDs were closed with a patch (n=11) or direct sutures (n=4), and the procedures were assisted by using a thoracoscope. There were 3 cases of tricuspid repair and 1 case of mitral valve repair. The mean CPB time and aortic occlusion time were $160{\pm}47\;and\;70{\pm}26 $minutes, respectively. Result: There was no mortality, but there were 3 minor complications (one pneumothorax, one wound dehiscence and one arrhythmia). The mean hospital stay was $5.9{\pm}1.8$ days. The mean follow-up duration was $10.7{\pm}6.4$ months. The follow-up echocardiogram noted no residual ASD or significant tricuspid regurgitation. Three patients suffered from pain or numbness. Conclusion: This study showed satisfactory clinical and cosmetic results. Although the operative time is still too long, more experience and specialized equipment would make this technique a good option for treating ASD.

• Journal of Chest Surgery
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• v.29 no.10
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• pp.1095-1101
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• 1996

From July 1983 to June 1995, 95 consecutive patients with mitral stenosis were treated surgically in the Department of Thoracic and Cardiovascular Surgery, Chonbuk national University Hospital, mitral valve replacement(MVR) in 62 patients and open mitral commissurotomy(OMC) in 33 patients. Mitral stenosis combined with coronary artery disease, with aortic valve disease, or wish mitral valvular Insufficiency, were excluded from this study. Surgical procedures for mitral stenosis were evaluated, according to complication, reoperation, mor- tality, nd functional change at mid- and long-term postoperative period. Cardiothoracic ratio in the MVR group was greater than the OMC group(0.59 $\pm$0.07 in MVR, 0.53 $\pm$0. 07 in OMC, p<0.05), but other variables(age, sex, MYHA functional classification, EKG finding, echocardiographic finding) did not show significant difference between two groups in the preoperative periods. Even though pathologic valvular lesion(Sellor's pathologic type m: 35 in MVR, 13 in OMC) and valvular calcification(35 in MVR, 11 in OMC) were severe in the MVR group(p=0.001) at intraoperative observation, OMC was possible in 11 patients(23.9%) among 46 patients with valvular calcification and in 13 patients(27.1 %) among 61 patients with Sellor's pathologic type IH . There was no significant difference in early and late mortality, actuarial survival(75% in MVR, 87.6% in OMC at 12 year), but early and late hemorrhagic, thromboembolic complications in the MVR group were greater than in the OMC. Functional changes in NYHA functional classification, EKG lEnding, cardiothoraclc ratio, and echocardiographic finding(EF, LVIDS, LWDd, LAD) did not differ between two groups in mid- and long-term postoperative periods. We conclude that our efforts for preservation of the native valve would be continued, because hemorrhagic and thromboembolic complications in the MVR were greater than in the OMC, and OMC was possible even in patients with severely stenotic and calcified mitral valve, although there was no sis-nificant difference in the functional change, mortality, and survival between the M VR and OMC.

• Journal of Chest Surgery
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• v.31 no.7
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• pp.679-683
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• 1998

From June 1995 to May 1997, we have implanted 52 Sorin Bicarbon mechanical valves in 41 patients. They were 16 men and 25 women, and their mean age was 47.4${\pm}$14.8(range; 18∼74 y.o.). 35(27 mm∼31 mm) were in mitral position, 15(19 mm∼25 mm) in aortic position, and 2(31 mm) in tricuspid position. 3 CABGs and a tumor excision were taken concomittantly. 35 patients were primary operation, and 6 were re-do operations. By intraoperative transesophageal doppler echocardiography, transvalvular peak/mean pressure gradient was 6.1${\pm}$2.7/2.4${\pm}$1.4 mmHg in mitral position and 27.6/10.7 mmHg in aortic position. The effective valve opening area in mitral position was 3.2${\pm}$0.6 cm2. Follow-up was total 508.6 patient-months, and mean follw-up was 12.7${\pm}$9.2 months. NYHA class was improved from 2.6${\pm}$0.6 to 1.2${\pm}$0.3 in average postoperatively. During that period, there was no operative death. 2 late non-valve related deaths were occurred. One was died of COPD, and the other was possible acute myocardial infarction. Among 7 postoperative complications, one valve related complication(minimal paravalvular leakage) was noticed. In conclusion, Sorin Bicarbon mechanical valve is believed one of the safe choice in clinical settings. It showed excellent hemodynamic and mechanical functions, and very low postoperative valve related complications in short term clinical experience.

• Journal of Chest Surgery
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• v.36 no.4
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• pp.242-254
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• 2003

Most of the studies conducted have investigated the beneficial effects of ischemic preconditioning on normothermic myocardial ischemia. However, the effect of preconditioning could be attenuated through the use of multidose cold cardioplegia as practiced in contemporary clinical heart surgical procedures. The purpose of this study was to investigate whether preconditioning improves postischemic cardiac function in a model of 25℃ moderate hypothermic ischemic heart induced by cold cardioplegia in isolated rat hearts. Material and Method: The isolated Sprague-Dawley rat hearts were randomly assigned to four groups. All hearts were perfused at 37℃ for 20 minutes with Krebs-Henseleit solution before the baseline hemodynamic data were obtained. Group 1 consisted of preconditioned hearts that received 3 minutes of global ischemic preconditioning at 37℃, followed by 5 minutes of reperfusion before 120 minutes of cardioplegic arrest (n=6). Cold (4℃) St. Thomas Hospital cardioplegia solution was infused to induce cardioplegic arrest. Maintaining the heart at 25℃, infusion of the cardioplegia solution was repeated every 20 minutes throughout the 120 minutes of ischemic period. Group 2 consisted of control hearts that underwent no manipulations between the periods of equilibrium and 120 minutes of cardioplegic arrest (n=6). After 2 hours of cardioplegic arrest, Krebs solution was infused and hemodynamic data were obtained for 30 minutes (group 1, 2: cold cardioplegia group). Group 3 received two episodes of ischemic preconditioning before 30 min of 37℃ normothermic ischemia and 30 minutes of reperfusion (n=6). Group 4 served as ischemic controls for group 3 (group 3, 4: warm ischemia group). Result: Preconditioning did not influence parameters such as left ventricular systolic pressure (LVSP), left ventricular end-diastolic pressure (LVEDP), rate-pressure product (RPP) and left ventricular dp/dt (LV dp/dt) in the cold cardioplegia group. (p=NS) However, preconditioning before warm ischemia attenuated the ischemia induced cardiac dysfunction, improving the LVSP, LVEDP, RPP, and LVdp/dt. Less leakage of CPK and LDH were observed in the ischemic preconditioning group compared to the control group (p<0.05). Conclusion: Ischemic preconditioning improved postischemic cardiac function after warm ischemia, but did not protect cold cardioplegic hearts.

• Journal of Chest Surgery
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• v.36 no.5
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• pp.242-254
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• 2003

Background: Most of the studies conducted have investigated the beneficial effects of ischemic preconditioning on normothermic myocardial ischemia. However, the effect of preconditioning could be attenuated through the use of multidose cold cardioplegia as practiced in contemporary clinical heart surgical procedures. The purpose of this study was to investigate whether preconditioning improves postischemic cardiac function in a model of $25^{\circ}C$ moderate hypothermic ischemic heart induced by cold cardioplegia in isolated rat hearts. Material and Method: The isolated Sprague-Dawley rat hearts were randomly assigned to four groups All hearts were perfused at 37$^{\circ}C$ for 20 minutes with Krebs-Henseleit solution before the baseline hemodynamic data were obtained, Group 1 consisted of preconditioned hearts that received 3 minutes of global ischemic preconditioning at 37$^{\circ}C$, followed by 5 minutes of reperfusion before 120 minutes of cardioplegic arrest (n=6). Cold (4$^{\circ}C$) St. Thomas Hospital cardioplegia solution was infused to induce cardioplegic arrest. Maintaining the heart at $25^{\circ}C$, infusion of the cardioplegia solution was repeated every 20 minutes throughout the 120 minutes of ischemic period. Group 2 consisted of control hearts that underwent no manipulations between the periods of equilibrium and 120 minutes of cardioplegic arrest (n=6). After 2 hours of cardioplegic arrest, Krebs solution was infused and hemodynamic data were obtained for 30 minuts (group 1, 2: cold cardioplegia group). Group 3 received two episodes of ischemic preconditioning before 30 min of 37$^{\circ}C$ normothermic ischemia and 30 minutes of reperfusion (n=6) Group 4 soloed as ischemic controls for group 3 (group 3, 4: warm ischemia group). Result: Preconditioning did not influence parameters such as left ventricular systolic pressure (LVSP), left ventricular end-diastolic pressure (LVEDP), rate-pressure product (RPP) and left ventricular dp/dt (LV dp/dt) in the cold cardioplegia group. (p=NS) However, preconditioning before warm ischemia attenuated the ischemia induced cardiac dysfunction, Improving the LVSP, LVEDP, RPP, and LV dp/dt. Less leakage of CPK and LDH were observed in the ischemic preconditioning group compared to the control group (p<0.05). Conclusion: Ischemic preconditioning improved postischemic cardiac function after warm ischemia, but did not protect cold cardioplegic hearts.

• Journal of Chest Surgery
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• v.41 no.2
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• pp.216-222
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• 2008

Background: Prosthetic annuloplasty rings are used for the reconstruction of the mitral valve annulus. However, there is controversy over the best ring to use for reconstruction. In this study, we evaluated the long term result of using a Teflon felt strip as an alternative to commercial rings. Material and Method: From 1996 to 2007, we enrolled 47 patients with pure mitral regurgitation greater than grade III. All patients had an ejection fraction of 40% or more. Patients with congenital heart disease or other valvular heart disease were excluded from this study. They were divided into two groups; the commercial ring group (Group CR) and the Teflon felt ring group (Group TF). Result: There was no mortality. The postoperative echocardiography showed no significant change in the overall ejection fraction (from $58.0{\pm}11.2%\;to\;42.8{\pm}8.4%$). There were no significant differences between the two groups with regard to morbidity, the reoperation rate and recurrence of mitral regurgitation greater than grade II. Conclusion: The long term results from this study showed that posterior mitral annuloplasty using Teflon felt had similar results compared to annuloplasty using commercial rings.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.06a
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• pp.311-318
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• 2005

Transparency on the Total System Performance Assessment (TSPA) is the key issue to enhance the public acceptance for a permanent high level radioactive repository. To approve it, all performances on TSPA through Quality Assurance is necessary. The integrated Cyber R&D Platform is developed by KAERI using the T2R3 principles applicable for five major steps in R&D's. The proposed system is implemented in the web-based system so that all participants in TSPA are able to access the system. It is composed of FEAS (FEp to Assessment through Scenario development) showing systematic approach from the FEPs to Assessment methods flow chart, PAID (Performance Assessment Input Databases) showing PA(Performance Assessment) input data set in web based system and QA system receding those data. All information is integrated into Cyber R&D Platform so that every data in the system can be checked whenever necessary. For more user-friendly system, system upgrade included input data & documentation package is under development. Throughout the next phase R&D, Cyber R&D Platform will be connected with the assessment tool for TSPA so that it will be expected to search the whole information in one unified system.

• Proceedings of the Korean Geotechical Society Conference
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• 1998.05a
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• pp.35-81
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• 1998

Distinct Element Method(DEM) has a great advantage to model the discontinuous behaviour of jointed rock masses such as rotation, sliding, and separation of rock blocks. Geometrical data of joints by a field monitoring is not enough to model the jointed rock mass though the results of DE analysis for the jointed rock mass is most sensitive to the distributional properties of joints. Also, it is important to use a properly joint law in evaluating the stability of a jointed rock mass because the joint is considered as the contact between blocks in DEM. In this study, a stochastic modelling technique is developed and the dilatant rock joint is numerically modelled in order to consider th geometrical and mechanical properties of joints in DE analysis. The stochastic modelling technique provides a assemblage of rock blocks by reproducing the joint distribution from insufficient joint data. Numerical Modelling of joint dilatancy in a edge-edge contact of DEM enable to consider not only mechanical properties but also various boundary conditions of joint. Preprocess Procedure for a stochastic DE model is composed of a statistical process of raw data of joints, a joint generation, and a block boundary generation. This stochastic DE model is used to analyze the effect of deviations of geometrical joint parameters on .the behaviour of jointed rock masses. This modelling method may be one tool for the consistency of DE analysis because it keeps the objectivity of the numerical model. In the joint constitutive law with a dilatancy, the normal and shear behaviour of a joint are fully coupled due to dilatation. It is easy to quantify the input Parameters used in the joint law from laboratory tests. The boundary effect on the behaviour of a joint is verified from shear tests under CNL and CNS using the numerical model of a single joint. The numerical model developed is applied to jointed rock masses to evaluate the effect of joint dilation on tunnel stability.