• Journal of Chest Surgery
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• v.28 no.11
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• pp.1038-1044
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• 1995

We have been used cryopreserved homograft valves for right ventricular outflow tract[RVOT reconstruction since November 1993. The homograft valves were harvested from the hearts of brain dead patients or hearts of transplant recipients. There were 12 male and 10 female patients. Their ages ranged from 5 months to 13 years[mean age,39.2 $\pm$ 37.4 months and the weight ranged from 5 to 48kg [mean weight, 13.7$\pm$ 9. l kg . The diagnoses included pulmonary atresia with ventricular septal defect [n=14 , tetralogy of Fallot[n=4 , truncus arteriosus[n=3 , and double outlet right ventricle with pulmonic stenosis[n=l .Monocuspid homograft patches were used for RVOT widening or REV[reparation l`etage ventriculaire operations in 4 patients. We also used homograft as valved conduits for RVOT reconstruction in 17 patients and left ventricular outflow tract reconstruction in anatomically corrected transposition in 1 patient. Among them size-reducing technique [converting a tricuspid valved conduit into a bicuspid valved conduit were applied to six patients for the correction of size mismatching. The mean follow-up period was 10.6 $\pm$ 5.4 months. There was one operative death[4.5% due to bleeding and one reoperation for removal of vegetation on the homograft leaflet. Postoperative echocardiography documented no significant homograft insufficiency and RVOT obstructions.In short-term, the homograft valves provide excellent hemodynamic characteristics, even though further studies are necessary to evaluate the long-term results.

• International Journal of Vascular Biomedical Engineering
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• v.1 no.1
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• pp.41-47
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• 2003

The patency rates of small diameter vascular grafts are disappointing because of the formation of thrombus and intimal hyperplasia. Among the various factors influencing the success of graft surgery, the compliance and the size of a graft are believed to be the most important physical properties of a vascular graft. Mismatch of compliance and size between an artery and a graft alters anastomotic flow characteristics, which may affect the formation of intimal hyperplasia. Among the hemodynamic factors influencing the development of intimal hyperplasia, the wall shear stress is suspected as the most important one. The wall shear stress distributions are experimentally measured near the end-to-end anastomosis models in order to clarify the effects of compliance and diameter mismatch on the hemodynamics near the anastomosis. The effects of radial wall motion, diameter mismatch and impedance phase angle on the wall shear rate distributions near the anastomosis are considered. Compliance mismatch generates both different radial wall motion and instantaneous diameter mismatch between the arterial portion and the graft portion during a flow cycle. Mismatch in diameter seems to be affecting the wall shear rate distribution more significantly compared to radial wall motion. The impedance phase angle also affects the wall shear rate distribution.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.11
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• pp.1585-1596
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• 2002

The objectives of the present study are to numerically and experimentally investigate the steady and pulsatile flow phenomena in the circular tubes, to quantitatively compare the flow characteristics of Newtonian and non-Newtonian fluids, and to find meaningful hemodynamic information through the flow analysis in the human blood vessels. The particle image velocimetry is adopted to visualize the flow fields in the circular tube. and the results from the particle image velocimetry are used to validate the results of the numerical analysis. In order to investigate the blood flow phenomena in the circular tube. constitutive equations, which are suitable to describe the rheological properties of the non-Newtonian fluids. are determined, and the steady and pulsatile momentum equations are solved by the finite volume prediction. The velocity vectors of the steady and pulsatile flow in the circular tube obtained by the particle image velocimetry arc in good agreement with those by the numerical analysis. For the given mass flow rate. the axial velocity profiles of the Newtonian and the non-Newtonian fluids appear differently. The pulsatile flow phenomena of the Newtonian and the non-Newtonian fluids are quite different from those of the steady flow.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.2
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• pp.153-159
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• 2012

Bypass anastomosis is frequently adopted for surgical treatments of stenosed coronary arteries. Optimal coronary bypass grafting should be investigated to improve the patency in arterial bypass techniques. The objective of this study is to analyze the effects of Y-grafting bypasses and T-grafting bypasses for various bifurcation and anastomotic angles. In order to find the optimal geometric configuration, the hemodynamic characteristics are obtained and compared with each other for different geometries. We found that both the left anterior descending artery (LAD) and left circumflex artery (LCX) blood flows were distributed evenly when the bypass grafting angle and bifurcated angle were $30^{\circ}$ and $15^{\circ}$, respectively,.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.1 s.244
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• pp.87-94
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• 2006

This paper presents the hydrodynamic design and performance analysis method for a miniaturized centrifugal blood pump using three-dimensional computational fluid dynamics (CFD) code. In order to obtain the hydraulically high efficient configuration of a miniaturized centrifugal blood pump for cardiopulmonary circulation, a well-established commercial CFD code was incorporated considering detailed flow dynamic phenomena in the blood pump system. A prototype of centrifugal blood pump developed by the present design and analysis method has been tested in the mock circulatory system. Predicted results by the CFD code agree very well with in vitro hydraulic performance data for a centrifugal blood pump over the entire operating conditions. Preliminary in vivo animal testing has also been conducted to demonstrate the hemodynamic feasibility for use of centrifugal blood pump as a mechanical circulatory support. A miniaturized centrifugal blood pump developed by the hydraulic design optimization and performance prediction method presented herein shows the possibility of a good candidate for intra and extracorporeal cardiopulmonary circulation pump in the near future.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.585-590
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• 2001

The hemodynamic characteristics were compared using commercial CFD code for the stenosed coronary and abdominal arteries. Numerical calculations were carried out in the axisymmetric arteries over the stenotic diameter ratios ranging from 0.25 to 0.875 (6 cases) employing the typical physiological flow conditions. In case of the coronary artery, there was only one recirculation zone observed distal to the stenosis throat during the major portion of the period. However, in case of the abdominal aorta, there were complex recirculation regions found proximal and distal to stenosis throat. For both models, the wall shear stresses(WSS) increased sharply in the converging stenosis, reaching a peak just upstream of the throat, and became negative or low values in the post-stenotic recirculation region. As the results, the oscillatory shear index(OSI) was abruptly increased at the stenosis throat. For the coronary stenosis model, the second peak in the OSI was observed distal to the stenosis. The distance between the first peak and the second peak was increased as the degree of the stenosis was raised. On the orther hand, the abdominal stenosis model showed a complex oscillatory behavior in the OSI index and did not showed such a strong second peak. As the degree of stenosis was increased, recirculation regions of the both arteries were extended much longer and flow pattern became more complex.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.10-12
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• 2008

Hemodynamic features of blood flow in the abdominal aorta aneurysm (AAA) are very important, because they are closely related with the rupture of aneurysm to death. It has been considered that the wall shear stress of blood flows influences the formation, growth, and rupture of AAA. On this account, it is important to understand the flow structure of blood in the aneurysm. In this study, the whole velocity field information inside a typical AAA was measured using an in vitro AAA model under the pulsatile flow condition. The vessel geometry was reconstructed based on the computerized tomography (CT) data of a patient. The AAA model was made by using a rapid prototyping (RP) method, based on the reconstructed vessel geometry. Velocity fields in the AAA model were measured at different pulsatile phases using a PIV (particle image velocimetry) system. As experimental results, a large-scale vortex is formed inside the AAA model and the vortices located near the AAA wall are supposed to increase the local pressure and wall shear stress. In this study, the AAA wall stress found to be was one of the most important governing parameters giving rise to the ruptured aneurysm.

• Journal of Trauma and Injury
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• v.22 no.2
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• pp.161-166
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• 2009

Purpose: This study was conducted to analyze chest-trauma patients and the old-aged patients with a traumatic hemopneumothorax. Methods: We reviewed the medical records of 101 chest-trauma patients admitted to the department of cardiovascular and thoracic surgery from June 1999 to November 2008. We evaluated the general characteristics of the chest-trauma patient, especially those of old-aged patients with a traumatic hemopneumothorax. Results: Rib fracture was observed in 99 of the cases, the location distribution was right: left =261: 255, with right being dominant. Rib fractures commonly involved the 4th and the 7th rib. The average number of rib fractures was 5.1, and the average number of rib fractures in the old-aged patients was significantly higher than that in the non-old-aged patients (p=0.04). There were 17 cases of a hemopnuemothorax in old-aged patients, 52 cases in non-old-aged patients. The blood loss through the chest tube for old-aged patients was significantly more than that for the non-old-aged patients, and the initial hemoglobin level was lower in the old-aged patients. Conclusion: Elderly trauma patients are more likely to die after trauma than other age groups. Even with relatively stable vital signs, invasive hemodynamic monitoring and intensive treatment are recommended.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.1
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• pp.39-44
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• 2002

The arterial stenosis related to the intimal thickening of the arterial wall is the main cause of many diseases in human cardiovascular system. Hemodynamic behavior of the blood flow is influenced by the presence of the arterial stenosis. In this study, effects of the pulsatile flow, caused by the periodic motion of the heart, on the blood flow and its interaction with the arterial stenosis are analyzed by the FEM-based computational fluid dynamics. As a result, it was found that the characteristics of the pulsatile flow in the artery with stenosis are quite different from those of the steady flow. And, the pulsatile flow condition affects the wall shear stress, which is one of the most important physiological parameters in the hemodynamics.

• Journal of Korean Critical Care Nursing
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• v.7 no.2
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• pp.14-23
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• 2014

Purpose: The purpose of this study was to provide basic information to develop appropriate nursing guidelines for cardiac telemetry. Methods: This retrospective research was conducted to identify the current usage of cardiac telemetry and considered 1,000 patients hospitalized for telemetry. The collected data were analyzed using IBM (SPSS Statistics for Windows 21.0). Results: Four-hundred and ninety-two patients (49.2%) were diagnosed with arrhythmia and 209 (20.9%) with heart failure. Electrocardiogram (ECG) rhythm changes were detected via telemetry in 464 cases. Major arrhythmias were ventricular tachycardia (183, 39.4%) and bradycardia (99, 21.3%). Interventions after detecting arrhythmia were cardioversion (16, 3.4%), defibrillation (1, 0.2%), and cardiopulmonary cerebral resuscitation (5, 1.1%); other patients were treated conservatively with close observation (381, 82.1%). Conclusion: There was appropriate intervention in 46.4% of the considered cases with the detection of ECG changes before patient notification, which implied that cardiac telemetry could be considered for application to patients with hemodynamic instability. Clear standards and guidelines are required to determine who requires telemetry and when to end the telemetry monitoring.