Artificial Heart System Research Articles

An Artificial Heart System for Testing and Evaluation of Cardiac Pacemakers

The usability assessment of a pacemaker is a complex task where the dedicated programmer for testing programmed algorithms is necessary. This paper provides the outcomes of development and complex testing of the artificial cardiac system to evaluate the pacemaker’s functionality. In this work, we used the modular laboratory platform ELVIS II and created graphical user interface in LabVIEW programming environment. The electrical model of the heart allows signals generation (right atrium, right ventricle) and the monitoring of the stimulation pulses. The LabVIEW user interface allows to set the parameters of the generated signals and the simulation of the cardiac rhythm disorders as well as the monitoring and visualization of the pacemaker behavior in real-time. The results demonstrate the capability of proposed system to evaluate the paced and sensed pulses. The proposed solution allows the scientists to test the behavior of any cardiac pacemaker for its pre-programmed settings and pacing mode. In addition, the proposed system can simulate various disorders and test cardiac pacemakers in different working modes.

Development of the single ventricle heart mathematical model based on the equation of forced oscillations

Not only protozoa being the simplest organisms have a single ventricle heart. Artificial heart systems used in cardiac surgery can be also of the single-ventricle design. Besides, there is a “single-ventricle heart condition”, i.e. a complex of defects in the structure of the heart that may occur in some human individuals and that may be found with different occurrence rate and severity. This defect should be attributed to an uneven development and malformation of some individual heart segments in the prenatal period. Single Ventricle belongs to the category of congenital heart defects. The latter greatly increases the scientific interest in studying the features of mathematical models of the single-ventricle heart condition. Herein, we offer our study on some issues of the smoothness of sewing of the exact solutions of a mathematical model of a single-ventricle heart based on the equation of forced oscillations.

Histological investigation of the titanium fiber mesh with one side sealed with non-porous material for its application to the artificial heart system.

In this study, we investigated tissue-inducing characteristics of a titanium fiber mesh disk with one surface sealed with a non-porous material. We used sintered titanium fiber mesh (Hi-Lex Co., Zellez™, Hyogo, Japan) having a titanium fiber diameter of 50µm and volumetric porosity of the titanium fiber mesh of 87% with an average pore size of 200µm. The titanium fiber mesh is disk-shaped with a dimeter of 5mm and a thickness of 1.5mm. One side of the titanium fiber mesh disk was sealed with silicone rubber adhesive that has no venomousness and the sealed titanium fiber mesh disks were implanted in rats under the skin of the dorsal region, and they were extracted in the 4th and 12th postoperative weeks. We investigated the distribution of capillaries; also we estimated the extent of the spread of oxygen from capillaries using the diffusion equation. Microscopic observation showed that the distribution of capillaries was mainly confined to the area around the sealed titanium fiber mesh disk and that connective tissue inside the sealed titanium fiber mesh disk seemed to be in a poor condition. From estimation of the extent of the spread of oxygen from capillaries, an area in which oxygen was poorly supplied may exist in the center of the sealed titanium fiber mesh disk. In conclusion, for application of the sealed titanium fiber mesh to an artificial heart system, the thickness of the titanium fiber mesh is an important factor for keeping the inside tissue in a healthy condition.

Current state of total artificial heart therapy and introduction of the most important total artificial heart systems.

Due to the declining instances of organ donation, total artificial heart (TAH) therapy is of increasing importance for the management of end-stage biventricular heart failure. We introduce the currently most important established and novel TAH systems (SynCardia, CARMAT, ReinHeart, BiVACOR), report clinical outcomes and discuss technical requirements for the successful implementation of TAH therapy as an alternative to cardiac transplantation.

Develoment and clinical application of artificial heart and circulatory support systems based on progressive medical-engineering collaboration

Develoment and clinical application of artificial heart and circulatory support systems based on progressive medical-engineering collaboration

Prototype of Total Artificial Heart System

Prototype of Total Artificial Heart System

Thermal State of Implantable Mechatronic Unit for Pulsative Total Artificial Heart

One of the important problems of implantable artificial heart systems development is ensuring of their continuous work during of all time of implantation in the limited heat transfer conditions. Temperature of the mechatronic unit housing shouldn't exceed forty degrees Celsius, and the overheating to forty-two degrees Celsius is admissible only in short-time modes. For the solution of this problem the numerical simulations of a thermal condition of implantable part of artificial heart mechatronic unit was carried out and based on results of the solution of a stationary task of heat conductivity. For the solution a stationary task of heat conductivity the finite-element analysis system ANSYS Workbench was used. The Finite-element model parameters are the following: number of nodes 642263 nodes, number of hexahedral finite-elements 363231, average length of the rib 1mm. Modeling was carried out for various power of thermal losses: 5, 8, 10 watts for which thermal stream density are 1500, 2400 and 3000 watts per square meter, respectively. The increasing of power of thermal losses from 5 to 10 watts increases the maximum temperature of surface of the mechatronic unit housing by only 6 degrees from thirty-three to thirty-nine degrees Celsius. The carried-out simulation of the established thermal state at various power of thermal losses showed lack of an overheat of a surface of the mechatronic unit housing above critical temperature during the continuous work for a long time and principle possibility of application of the developed design as implantable system.

Histological observation of the titanium mesh and application to the artificial heart system

Histological observation of the titanium mesh and application to the artificial heart system

Design and Analysis of a Halbach Magnetized Magnetic Screw for Artificial Heart

Due to the limited number of the donor hearts, artificial heart (AH) systems are required for the therapy of the terminal heart diseases [1]. Existing electric-drive AHs employ the rotary blood pumps or linear motors, but suffering from blood damage and poor thrust density, respectively [2]. Very recently, the concept of magnetic screw was proposed. The magnetic screw actuator integrated with permanent magnet (PM) brushless machine is capable of converting rotational motion into linear motion and vice versa [3]. Since it offers high force density, wear-free, small size and light weight, magnetic screw actuator has a bright future in AH applications. The purpose of this paper is to propose and analyze a new magnetic screw with the halbach PM array [4], which offers improved force density.

Manifestations of Atrial Tamponade in a Patient Implanted with SynCardia Total Artificial Heart


 
 
 
 
 Implantation rates of the SynCardia Total Artificial Heart (TAH) system is growing owing to the increasing incidence of biventricular heart failure and the limited number of transplantable hearts. Among the complications associated with the device, atrial tamponade is an emergent condition that requires immediate attention. Atrial tamponade occurs when increasing pericardial hemorrhage leads to atrial compression that produces tamponade physiology and compromises cardiac output. Unfortunately to our knowledge, information concerning the early manifestations of tamponade in TAH patients is extremely scarce. Previous reports have focused on decreased cardiac output as an indicator of tamponade. However, other presentations including pulmonary decompensation are largely undescribed. This case provides a valuable account of the early manifestations of atrial tamponade observed prior to diminished cardiac output.
 
 
 
 

ウェアラブル全置換型人工心臓システム用小型空気圧駆動装置の開発

ウェアラブル全置換型人工心臓システム用小型空気圧駆動装置の開発

System overview of the fully implantable destination therapy--ReinHeart-total artificial heart.

Owing to the lack of suitable allografts, the demand for long-term mechanical circulatory support in patients with biventricular end-stage heart failure is rising. Currently available Total Artificial Heart (TAH) systems consist of pump units with only limited durability, percutaneous tubes and bulky external equipment that limit the quality of life. Therefore we are focusing on the development of a fully implantable, highly durable destination therapy total artificial heart. The ReinHeart-TAH system consists of a passively filling pump unit driven by a low-wear linear drive between two artificial ventricles, an implantable control unit and a compliance chamber. The TAH is powered by a transcutaneous energy transmission system. The flow distribution inside the ventricles was analysed by fluid structure interaction simulation and particle image velocimetry measurements. Along with durability tests, the hydrodynamic performance and flow balance capability were evaluated in a mock circulation loop. Animal trials are ongoing. Based on fluid structure interaction simulation and particle image velocimetry, blood stagnation areas have been significantly reduced. In the mock circulation loop the ReinHeart-TAH generated a cardiac output of 5 l/min at an operating frequency of 120 bpm and an aortic pressure of 120/80 mmHg. The highly effective preload sensitivity of the passively filling ventricles allowed the sensorless integration of the Frank Starling mechanism. The ReinHeart-TAH effectively replaced the native heart's function in animals for up to 2 days. In vitro and in vivo testing showed a safe and effective function of the ReinHeart-TAH system. This has the potential to become an alternative to transplantation. However, before a first-in-man implant, chronic animal trials still have to be completed.

Fundamental Examination of an Application of Wearable Pneumatic Drive Unit for Pneumatic Total Artificial Heart System

Fundamental Examination of an Application of Wearable Pneumatic Drive Unit for Pneumatic Total Artificial Heart System

Fundus Fluorescein Angiographic Findings in Patients Who Underwent Ventricular Assist Device Implantation

Disruption of microcirculation in various tissues as a result of deformed blood rheology due to ventricular assist device (VAD) implantation causes novel arteriovenous malformations. Capillary disturbances and related vascular leakage in the retina and choroidea may also be seen in patients supported by VADs. We aimed to evaluate retinal vasculature deteriorations after VAD implantation. The charts of 17 patients who underwent VAD implantation surgery for the treatment of end-stage heart failure were retrospectively reviewed. Eight cases (47.1%) underwent pulsatile pump implantation (Berlin Heart EXCOR, Berlin Heart Mediprodukt GmbH, Berlin, Germany); however, nine cases (52.9%) had continuous-flow pump using centrifugal design (HeartWare, HeartWare Inc., Miramar, FL, USA). Study participants were selected among the patients who had survived with a VAD for at least 6 months, and results of detailed ophthalmologic examinations including optic coherence tomography (OCT) and fundus fluorescein angiography (FA) were documented. All of the 17 patients were male, with a mean age of 48.5 ± 14.8 years (15-67 years). Detailed ophthalmologic examinations including the evaluation of retinal vascular deteriorations via FA were performed at a mean of 11.8 ± 3.7 months of follow-up (6-18 months). Mean best-corrected visual acuity and intraocular pressure were found as logMAR 0.02 ± 0.08 and 14.6 ± 1.9 mm Hg, respectively in the study population. Dilated fundoscopy revealed severe focal arteriolar narrowing in two patients (11.8%), and arteriovenous crossing changes in four patients (23.5%); however, no pathological alteration was present in macular OCT scans. In patients with continuous-flow blood pumps, mean arm-retina circulation time (ARCT) and arteriovenous transit time (AVTT) were found to be 16.8 ± 3.0 and 12.4 ± 6.2 s, respectively; whereas those with pulsatile-flow blood pumps were found to be 17.4 ± 3.6 and 14.0 ± 2.1 s in patients (P=0.526 and P=0.356, respectively). FA also revealed a tendency for increased frequency of dye leakage from the optic disc in our study population. Except for remarkable delays in both ARCT and AVTT as well as a tendency for increased frequency of dye leakage from the optic disc, ophthalmologic evaluations revealed no other significant pathology or vascular deterioration in the retina that could be attributed to artificial heart systems.

Experimental validation of the linear drive train for a total artificial heart system

In industrialized countries cardiovascular diseases are the major cause of death. Beside heart transplants, which are a limited option due to the limited number of available human donor hearts, Total Artificial Hearts (TAHs) are the only therapy available for some patients with terminal heart diseases. For various reasons a total implantable artificial heart is desirable, but also sets restrictions in terms of weight and dimensions due to the limited space in the human thorax. Therefore a precise requirement profile is needed for the drive design to provide sufficient force for the blood pump and to avoid oversizing of the drive and to prevent blood damage by overheating.

Magnetic-Field Immunity Examination and Evaluation of Transcutaneous Energy-Transmission System for a Totally Implantable Artificial Heart

Transcutaneous energy transmission (TET) is the most promising noninvasive method for supplying driving energy to a totally implantable artificial heart. Induction-heating (IH) cookers generate a magnetic flux, and if a cooker is operated near a transcutaneous transformer, the magnetic flux generated will link with its external and internal coils. This will affect the performance of the TET and the artificial heart system. In this paper, we present the design and development of a coil to be used for a magnetic immunity test, and we detail the investigation of the magnetic immunity of a transcutaneous transformer. The experimental coil, with five turns like a solenoid, was able to generate a uniform magnetic field in the necessary bandwidth. A magnetic-field immunity examination of the TET system was performed using this coil, and the system was confirmed to have sufficient immunity to the magnetic field generated as a result of the conventional operation of induction-heating cooker.

인공심장의 예측 가능한 제어를 위한 실시간 소프트웨어 설계 구조의 개선

실시간 소프트웨어 설계 구조 중의 하나인 시간 구동 구조 (TTA: Time-Triggered Architecture)는 미리 정해진 시간에 따라 특정 태스크를 수행하기 때문에 소프트웨어의 동작을 예측하기 쉽지만 이의 적용을 위해서는 시스템의 시간 제약성을 만족시키는 설계 과정이 필수적이다. 반면 이벤트 구동 구조 (ETA: Event-Triggered Architecture)는 외부의 이벤트가 발생함에 따라 대응되는 태스크를 수행하는 방식으로 소프트웨어의 구조가 직관적이고 이벤트에 대한 반응 시간이 빠르며 확장이 용이하다. 그러나 이 구조는 다양한 이벤트 발생 상황에 대한 시스템 동작의 예측이 어려워서 높은 안전도가 필요한 시스템 구현에 많이 사용되고 있지 않다. 많은 관련 연구에서 높은 안전도가 필요한 안전 지향 시스템에 TTA를 적용 할 것을 권장되지만, 실제 구현에 있어서는 이의 적용에 필요한 실시간성 분석에 많은 노력이 소요되고, 소프트웨어 공학기술 적용에 대한 인식 부족으로 TTA의 적용이 많지 않은 실정이다. 본 논문은 인간의 생명과 직결되어 이에 따른 실시간성과 안전성이 요구되는 인공심장 제어 시스템에 내장된 소프트웨어 구조를 TTA 기반으로 개선한 연구를 기술한다. 본 연구에서는 인터럽트 측정 소프트웨어를 구현하여 기존에 내장된 실시간 소프트웨어가 가진 태스크의 시간적 속성을 파악하고 RMA (Rate-Monotonic Analysis) 실시간 분석 기법을 통해 시스템의 실시간성을 만족할 수 있도록 설계를 개선하였다. 또한, 이를 바탕으로 인공심장 제어 소프트웨어의 구현을 개선하여 다양한 실험을 통해 개선된 TTA 기반의 소프트웨어를 탑재한 인공심장 시스템은 시스템의 동작 예측도를 획기적으로 높여주면서 기존의 인공심장 시스템과 동일하게 동작함을 확인하였다. Time-Triggered Architecture (TTA), one of real-time software design paradigms which executes tasks in timely manner, has long been advocated as being better suited in fore-sighting system behavior than event-triggered architecture (ETA). To gain this valuable feature of TTA, however, precise task designing process is mandatory. Alternatively, ETA tries to execute tasks whenever paired events are occurred. It provides intuitive and flexible basement to add/remove tasks and, moreover, better response time performance. However ETA is difficult to analyze because system behavior might be different depending on the order of interrupts detected by the system. Many previous researches recommended TTA when developing safety-critical real-time systems, but cost problem of task designing process and insufficient consensus for applying rigorous software engineering practice are still challenging in practice. This paper describes software refactoring process which applying TTA approach into ETA based embedded software in artificial heart system. We implemented dedicated interrupt monitoring program to capture existing tasks' real-time characteristics. Based on the captured information, proper task designing process is done. Real-time analysis using RMA (Rate-Monotonic Analysis) verified that new design guarantees timeliness of the system. Empirical experiments revealed that revised design is as efficient, when measured in terms of system's external output, as the old design and enhances predictability of the system behavior as well.

Development and clinical application of the next-generation artificial heart systems

Development and clinical application of the next-generation artificial heart systems

Development of an electrohydraulic total artificial heart system: Improvement of pump unit

AbstractAn electrohydraulic total artificial heart (EHTAH) system has been developed. The EHTAH system consists of diaphragm‐type blood pumps, and electrohydraulic actuator, an internal control unit, a transcutaneous energy transfer system (TETS), a transcutaneous optical telemetry system (TOTS), and an internal battery. The reciprocating rotation of the impeller generates oil pressure that drives the blood pumps at alternating intervals. The blood pumps and the actuator were successfully integrated into the pump unit without oil conduits. As a result of miniaturizing the blood pumps and the actuator, the displacement volume and weight of the EHTAH system were decreased to 872 ml and 2492 g, respectively. Furthermore, the maximum flow rate and efficiency increased up to 12 L/min and 15.4%. The pump units and the EHTAH systems were successfully implanted in 36 calves weighing from 55 to 87 kg. In the longest case, a calf with the pump unit survived for 87 days and a calf with the EHTAH system survived for 70 days. The EHTAH system was powered by the TETS, and was powered every day by the internal battery for 40 minutes. These results indicate that the EHTAH system has the potential to become a fully implantable cardiac replacement system. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(9): 34–46, 2010; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10220

The Current Status of Heart Transplantation and the Development of „Artificial Heart Systems“

In view of the major technical advances in ventricular assist devices (VAD) in recent years, the authors discuss the question whether these "artificial hearts" are still no more than a temporary measure for patients awaiting heart transplantation (HTx), or whether they can already be used as an independent form of long-term treatment. Statistics from Eurotransplant regarding heart transplantations and transplant waiting lists in Germany are presented. Technical developments in cardiac support systems, the variation in results depending on the indication, and the findings with respect to quality of life are all discussed on the basis of a selective review of the literature and the authors' own clinical experience. The waiting list for heart transplantation in Germany has grown to a record size of nearly 800 patients, while fewer than 400 hearts are transplanted each year. Technical advances have improved outcomes in VAD therapy, but the outcome depends on the patient's preoperative condition. The physical performance of patients who have received VAD is comparable to that of HTx patients; nonetheless, HTx patients have a better quality of life. Chronic VAD therapy has become a clinical reality. Because of the greater number of patients awaiting HTx, many will not receive their transplants in time. When the decision to treat with VAD is made early, it can be used as an alternative form of treatment with a comparable one-year survival (>75%).