• 대한의용생체공학회:의공학회지
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• 제25권1호
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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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• 제1권1호
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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.

• 대한기계학회논문집B
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• 제38권8호
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• pp.715-720
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• 2014

좌심실보조장치(LVAD)가 심실부하감소에 미치는 영향을 극대화 하기 위해, 심실보조장치 치료를 위한 최적의 심부전 심각도 단계를 찾는 것은 중요하다. 우리는 심부전 정도에 따른 LVAD 의 박동효율을 이론적으로 예측하였다. 우리는 혈관시스템의 6 컴파트먼트의 Wind-kessel 모델과 연동된 심실의 삼차원 유한요소모델을 사용하였다. 이 모델을 이용하여, LVAD 치료 하에서 심부전의 정도에 따라 심실의 수축성 ATP 소모율, 좌심실압력, 심박출량, 심박출 분획, 1 회심박출량 등과 같은 심장응답을 예측하였다. LVAD 치료 중에 에너지학적 부하조건을 암시하는 수축성 ATP 소모율은 5 단계 심부전 조건에서 가장 크게 감소하였다. 따라서, 우리는 LVAD 를 회복으로의 가교로서 고려하고 있을 때, 심부전 5 단계에서 LVAD 치료를 시작하는 것이 가장 적절하다는 결론을 내린다.

• Journal of Chest Surgery
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• 제53권5호
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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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• 제55권3호
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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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• 순환기질환의공학회 2001년도 제1회 학술대회 초록집
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• pp.16-17
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• 2001

• Journal of Chest Surgery
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• 제29권7호
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• pp.689-699
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• 1996

신개발한 전기 유압식 심실 보조장치의 생 체 내 성능 테스트와 상기 심실보조장치를 이용한 좌심실 보 조가 자연심장 좌심실의 기능에 미치는 영향을 평가하기 위한 동물실험을 고안하였다. 총 성숙 면양 8마리가 실험에 사용되었으며 이중 7마리로부터 자료 수집이 가능하였다. 심실 보조시 간은69분부터 7일 사이로 심실보조장치는 자연심장의 박동수범위 내에서 동기식 및 비동기식 방식 모 두 만족스럽게 작동하였으며, 좌심방 내의 음압의 발생 없이 주어진 정상 좌심방압 내에서 분당 4리터 이상의 보조 혈류량을 얻을 수 있었다. 심실보조 개시 3일 이후부터 혈중 유리혈색소의 급격한 증가를 보여 상당량의 용혈이 진행되고 있음 을 시사하였다. 또한 심실보조 후 혈액 남의 부동형 고분자판막(floating type polymer valve)에 소량의 혈 전이 발견되어 혈액적 합성 및 혈전저항성 면에 있어 보다 많은 연구 및 개선의 여지가 있음을시사하였 다. 심실보조시작후의 혈역학의 변화는혈류보조량분당2.0∼2.5리터 사이에서 자연심장의 박동수및 박출량과 좌심실 분당작업량(left ventricular minute work), 심내막 생육력비 (endocardial viability ratio), 흔합 정맥혈 및 관상동맥 정맥혈 산소량은 증가하는 소견을 보였으며,반대로 좌심실압 및 좌심방압과 좌심실압 변화율(left ventricular dp/dt)은 감소하는 소견을 보였다. 이중 심박출량의 변화 외에는 모두 통계적으로 유의한 차이를 보여 효과적 인 좌심실의 탈부하가 이루어지고 있음을 입증하였다. 또한 동기식 심실보조시 심내막 생육력비 및 관상정맥혈의 산소량은 비동기식 심실보조시와 비교할 때 역시 통계적으로 유의한 차이를 보여 동기식 심실보조에 의한 반박동(counterpulsation)이 심근의 관 류량을 증가시키며 따라서 손상된 심근의 회복에 유리 함을 시사하였다.

• Clinical and Experimental Pediatrics
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• 제50권11호
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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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• 제56권3호
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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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• 제57권3호
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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.