• Journal of Biomedical Engineering Research
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• v.25 no.1
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• pp.65-70
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• 2004

In this paper, we described 23 cases of animal experiment with our pneumatic ventricular assist device and new durability-improvement method. The blood pump consists of blood housing, and back plate made by the injection molding of isoplast, and the diaphragm fabricated by dipping of polyurethane solution onto the aluminum mold. Its volume was 75 $m\ell$ and in-vitro test showed that maximum output was 4.5 $\ell$/min at the 100 mmHg. The adult female sheep with weight of 50 ＋ 10 kg were employed for tile in-vivo experiments and the mean blood flow was sustained at 3.0 1/min. 4 animals survived more than 15 days and the longest survival time was 28 days. In the prior 10 cases, the major causes of death were the tearing of diaphragm at the diaphragm to blood housing junction. By the new mesh and alumina ball milling methods, the durability was enhanced, and its qualitative and quantitative improvement was proved via the in-vivo and in-vitro methods. Animal experiments demonstrated that all the physiologic parameters a ere maintained within the permissible ranges and no thrombus formation was observed through the visual and blood test. The in-vivo experiments demonstrated our pneumatic ventricular assist device to he one month's bridge to transplantation device.

• Advances in biomechanics and applications
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• v.1 no.1
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• pp.23-40
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• 2014

This paper examines the blood chamber of a left ventricular assist device (LVAD) under static loading conditions and standard operating temperatures. The LVAD's walls are made of a temperature-sensitive polymer (ChronoFlex C 55D) and are covered with a titanium nitride (TiN) nano-coating (deposited by laser ablation) to improve their haemocompatibility. A loss of cohesion may be observed near the coating-substrate boundary. Therefore, a micro-scale stress-strain analysis of the multilayered blood chamber was conducted with FE (finite element) code. The multi-scale model included a macro-model of the LVAD's blood chamber and a micro-model of the TiN coating. The theories of non-linear elasticity and elasto-plasticity were applied. The formulated problems were solved with a finite element method. The micro-scale problem was solved for a representative volume element (RVE). This micro-model accounted for the residual stress, a material model of the TiN coating, the stress results under loading pressures, the thickness of the TiN coating and the wave parameters of the TiN surface. The numerical results (displacements and strains) were experimentally validated using digital image correlation (DIC) during static blood pressure deformations. The maximum strain and stress were determined at static pressure steps in a macro-scale FE simulation. The strain and stress were also computed at the same loading conditions in a micro-scale FE simulation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.8
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• pp.715-720
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• 2014

In order to maximize the effect of left ventricular assist device (LVAD) on ventricular unloading, the therapy should be begun at appropriate level of heart failure severity. We predicted pumping efficacy of LVAD according to the severity of heart failure theoretically. We used 3 dimensional finite element model of ventricle coupled with 6 Wind-kessel compartmental model of vascular system. Using the computational model, we predicted cardiac responses such as contractile ATP consumption of ventricle, left ventricular pressure, cardiac output, ejection fraction, and stroke work according to the severity of ventricular systolic dysfunction under the treatments of continuous LVAD. Contractile ATP consumption, which indicates the ventricular energetic loading condition decreased maximally at the $5^{th}$ level heart-failure under LVAD therapy. We conclude that optimal timing for LVAD treatment is $5^{th}$ level heart-failure when considering LVAD treatment as "bridge to recovery".

• Journal of Chest Surgery
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• v.53 no.5
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• pp.306-309
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• 2020

A 59-year-old man presented for possible durable ventricular assist device (VAD) implantation. He had previously been diagnosed with congenitally corrected transposition of the great arteries, a ventricular septal defect, an atrial septal defect, pulmonary valve stenosis, and aortic valve regurgitation. In the previous 22 years, he had undergone palliative cardiac surgery 3 times. VAD implantation as a bridge to transplantation was planned. Owing to severe adhesions, mesocardia, a left ascending aorta, and moderate aortic regurgitation, we performed VAD implantation and aortic valve closure via a dual left thoracotomy and partial sternotomy.

• Journal of Chest Surgery
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• v.55 no.3
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• pp.197-205
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• 2022

Background: The integrated design of the HeartMate 3 (Abbott Laboratories, Chicago, IL, USA) affords flexibility to place the pump within the pericardium or thoracic cavity. We sought to determine whether the presence of a left ventricular assist device (LVAD) in either location has a meaningful impact on overall patient outcomes. Methods: A retrospective cohort study was conducted of all 165 patients who received a HeartMate 3 LVAD via a median sternotomy from November 2014 to August 2019 at our center. Based on operative reports and imaging, patients were divided into intrapleural (n=81) and intrapericardial (n=84) cohorts. The primary outcome of interest was in-hospital mortality, while secondary outcomes included postoperative complications, cumulative readmission incidence, and 3-year survival. Results: There were no significant between-group differences in baseline demographics, risk factors, or preoperative hemodynamics. The overall in-hospital mortality rate was 6%, with no significant difference between the cohorts (9% vs. 4%, p=0.20). There were no significant differences in the postoperative rates of right ventricular failure, kidney failure requiring hemodialysis, stroke, tracheostomy, or arrhythmias. Over 3 years, despite similar mortality rates, intrapleural patients had significantly more readmissions (n=180 vs. n=117, p<0.01) with the most common reason being infection (n=68/165), predominantly unrelated to the device. Intrapleural patients had significantly more infection-related readmissions, predominantly driven by non-ventricular assist device-related infections (p=0.02), with 41% of these due to respiratory infections compared with 28% of intrapericardial patients. Conclusion: Compared with intrapericardial placement, insertion of an intrapleural HM3 may be associated with a higher incidence of readmission, especially due to respiratory infection.

• 순환기질환의공학회:학술대회논문집
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• 2001.11a
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• pp.16-17
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• 2001

• Journal of Chest Surgery
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• v.29 no.7
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• pp.689-699
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• 1996

An animal experiment was designed for the evaluation of in vivo performance of the newly developed electrohydraulic type ventricular assist device and its influence on the left ventricular function during pal- satile left ventricular assist. Eight adult sheep were incorporated into the study and data were collected from seven sheep. Total as- sist time ranged from 69 minutes to 7 days. The performance of the device was satisfactory both in asyn- chr nous and synchronous mode within the range of given native heart rate. More than 4 liters of device output could be reached within the range of normal left atral pressure without development of negative pressure in the left atrium. Moderate to severe degree of hemolysis was noted as evidenced by significant increase of plasma free hemoglobin level after 3 days of left ventricular support along with the presence of the small amount of thrombi around the floating disc type polymer valve apparatus reflecting that further study and refinement of the device need to be done in regard of biocompatibility and thromboresistance. The hemodynamics showed increase in heart rate (p < 0.05), cardiac output and left ventricular minute work (p < 0.05) after placement of the device at the flow rate of 2.0∼2.5 Llmin. The left atrial pressure, left ventricular pressure and LV dpldt were decreased after the device placement(p < 0.05). The endocardial viability ratio and oxygen contents of the mixed ven us blood and coronary venous blood were all increased (p < 0.05) after the device placement suggesting effective unloading of the left ventricle was accomplished. The myocardial perfusion was thought improved in synchronous counterpulsation as suggested by sig- nificant increase in endocardial viability ratio and coronary venous blood oxygen content in synchronous assist mode comparing with asynchronous mode.

• Clinical and Experimental Pediatrics
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• v.50 no.11
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• pp.1041-1048
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• 2007

Not a few patients in children and adolescents are suffering from right ventricular (RV) dysfunction resulting from various conditions such as chronic lung disease, left ventricular dysfunction, pulmonary hypertension, or congenital heart defect. The RV is different from the left ventricle in terms of ventricular morphology, myocardial contractile pattern and special vulnerability to the pressure overload. Right ventricular failure (RVF) can be evaluated in terms of decreased RV contractility, RV volume overload, and/or RV pressure overload. The management for RVF starts from clear understanding of the pathophysiology of RVF. In addition to correction of the underlying disease, management of RVF per se is very important. Meticulous control of volume status, inotropic agents, vasopressors, and pulmonary selective vasodilators are the main tools in the management of RVF. The relative importance of each tool depends on the individual clinical status. Medical assist device and surgery can be considered selectively in case of refractory RVF to optimal medical treatment.

• Journal of Chest Surgery
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• v.56 no.3
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• pp.224-227
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• 2023

Median sternotomy is a standard surgical technique used for left ventricular assist device (LVAD) implantation. However, if sternotomy has a prohibitive surgical risk, LVAD implantation can be performed through only left thoracotomy. We managed a patient with end-stage heart failure who had recently undergone coronary artery bypass grafting (CABG) elsewhere. The patient also had a deep sternal wound infection and bacteremia. Because of refractory cardiogenic shock, we performed extracorporeal membrane oxygenation (ECMO). After multiple mediastinal washouts and omental flap placement, ECMO was converted to extracorporeal LVAD (from the left ventricular apex to the descending aorta) through a left thoracotomy. The extracorporeal LVAD was maintained for 18 days and replaced by the HeartMate 3 LVAD. The patient was discharged in good condition 115 days after CABG.

• Journal of Chest Surgery
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• v.57 no.3
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• pp.319-322
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• 2024

Venovenous extracorporeal membrane oxygenation (VV ECMO) is often used in cases of severe respiratory failure, especially in patients considered for lung transplantation. However, because many lung diseases can ultimately result in right heart failure, the treatment of secondary right heart failure can present a challenge when the patient is already under VV ECMO support. In such cases, an oxygenated-right ventricular assist device (OxyRVAD) can be used. OxyRVAD is designed to maintain anterograde blood flow and prevent right ventricular distension. Moreover, the pulmonary arterial cannula can be inserted percutaneously. We report a case in which percutaneous OxyRVAD was successfully implemented to manage right heart failure in a patient with respiratory failure who was on VV ECMO.