bluuebunny/crossref_metadata_2025 huggingface dataset:
Intrathoracic and Intraabdominal Wall Implantation of a Centrifugal Blood Pump for Circulatory Assist
Authors: Wakisaka Yoshinari , Taenaka Yoshiyuki , Chikanari Kenichi , Okuzono Yasuki , Nishimura Takashi , Endo Seiko , Nakatani Takeshi , Takano Hisateru
Published: March 2003

An implantable centrifugal pump (ICP) 320 ml in volume and 830 g in weight has been developed for prolonged circulatory assist. The antithrombogenicity of the ICP is provided by a balancing hole in the center of the impeller. The watertightness and histocompatibility of the ICP are supported by its silicone ring seal and its casing of titanium and acrylic resin, respectively. The total efficiency of the ICP was 30% at a 5 L/min flow rate and a 100 mm Hg head. The heat generation, watertightness, and anatomical fitting of the ICP were assessed in an intrathoracic implantation in a goat (66 kg) and in an intraabdominal wall implantation in a goat (70 kg). Warfarin was given for anticoagulation in each experiment to keep the prothrombin time around 1.7 times that of the control. The temperatures of the pump surface, the pleura, and the room were measured every 3 h. Anatomical fitting was evaluated by pathological observation after the termination of the experiment. The ICP could run for 40 days in the chest cavity and for 11 days in the abdominal wall. The temperature of the motor remained about 1.8°C higher than the reference in both experiments. The ICP was completely covered by a layer of smooth fibrous tissue. The moisture content of the seals remained normal. Although a small amount of atelectasis was found in the lingula, neither lung adhesion nor necrotic change of the chest wall was observed. The inflammation of the surrounding tissue including foreign body reaction and thermal burn was minimal. In conclusion, the ICP has satisfied in vivo testing of its watertightness, exothermicity, and anatomical fitting.
Eccentric Roller Type Total Artificial Heart Designed for Implantation
Authors: Sueshiro Masafumi , Fukunaga Shintaro , Hirai Shinji , Sueda Taijiro , Matsuura Yuichiro
Published: March 2003

In the process of developing a completely implantable total artificial heart system, we have made an eccentric roller type total artificial heart and evaluated it by means of a mock circulatory system and by an acute animal experiment. The actuator of the artificial heart consists of 2 cylindrical drum type rollers which squeeze 2 blood chambers. The blood chambers are made of silicone rubber and are torus in shape. There is no valve used in this artificial heart. The artificial heart appears to be a nearly circular cylinder, approximately 10 cm in length and 8 cm in diameter. In the Donovan mock test, the artificial heart worked at a roller speed of 100–125 rpm with flow rates of 2.5–3.0 L/min for the right side and 3.2–3.8 L/min for the left side, respectively. The electric power consumption was 19.0–24.7 W. Our artificial heart is characterized by an ejection of blood alternatively in the pulsatile mode without need for reversing the motor. In the ex vivo evaluation, circulation of an adult sheep was maintained with this artificial heart for 4 h.
Effect of Pressure‐Flow Relationship of Centrifugal Pump on In Vivo Hemodynamics: A Consideration for Design
Authors: Tagusari Osamu , Yamazaki Kenji , Litwak Philip , Antaki James F. , Watach Mary , Gordon Lisa M. , Kono Kunihisa , Mori Toshio , Koyanagi Hitoshi , Griffith Bartley P. , Kormos Robert L.
Published: March 2003

Abstract We have been developing centrifugal pumps for an implantable left ventricular assist device. We manufactured 2 prototype centrifugal pumps (PI, PII). These two have similar designs except for the PII having a volute casing and a large output port. To determine the differences in the hydraulic characteristics between the PI and PII, we carried out in vitro and in vivo experiments. In vitro study showed that the PII had a shallower H‐Q curve than that of the PI, and the PII required a pump speed faster than the PI for the same flow rate and pressure head. On the other hand, in vivo study showed that the PII demonstrated a flow pulsatility greater than that of the PI at 1,900 rpm and 8 L/min although no significant change was observed at low pump speeds (≤1,500 rpm). This greater pulsatility consisted of a large discharge according to the small differential pressure during the systolic phase and a small discharge according to the large differential pressure during the diastolic phase. In contrast, the PI, having the steeper H‐Q curve, showed a small discharge in the systolic phase and a large discharge in the diastolic phase. These results showed that pulsatility synchronized with the native heart beating depended on the slope of the H‐Q curve. As a result, the slope of the H‐Q curve is important to determine the component of pulsatility synchronized with native cardiac output. Regarding the slope of the H‐Q curve, a pump having a volute casing and a large outlet port demonstrates a shallow slope in the H‐Q curve. In conclusion, we suggest that a centrifugal pump for use in left ventricular aortic bypass should be designed considering the effect on the native heart pulsatility.
Hemodynamics and Survival of Patients with Acute Renal Failure Treated by Continuous Dialysis with Two Synthetic Membranes
Authors: Jones Colin H. , Goutcher Eddie , Newstead Charles G. , Will Eric J. , Dean Steven G. , Daviso Alex M.
Published: March 2003

Synthetic membranes are not identical and have specific interactions that may be harmful or beneficial. We have investigated the incidence of hypotension and the outcome of acute renal failure (ARF) in ventilated patients treated by continuous venovenous dialysis with 2 different synthetic membranes. In Study 1, the mean arterial pressure (MAP) and systemic vascular resistance (SVR) were monitored during the first 12 min of dialysis with polyacrylonitrile (PAN). In Study 2, the MAP and survival rates were compared in patients randomly assigned to either PAN or polysulfone. No subjects were receiving angiotensin converting enzyme inhibitors. In Study 1, the MAP decreased due to a reduction in the SVR during the first 6 min of dialysis but returned to the baseline value by 12 min in 22 patients during 27 dialysis treatments. In Study 2, the MAP was lower than the baseline value at 6 min during 233 dialysis treatments in 133 patients randomly assigned to PAN or polysulfone membranes (PAN group, 81.5 ± 15 to 78.7 ± 15.6 mm Hg, p =0.001; and polysulfone group, 81.3 ± 15.4 to 80.0 ± 15.7 mm Hg, p =0.06). Severe reductions in the MAP were seen during 13.2% of the PAN and 7.2% of the polysulfone treatments (χ2, p =NS). The age, APACHE II score, MAP, inotrope requirement, and primary diagnosis did not differ according to membrane material in a total of 197 consecutive patients (PAN, n =97; polysulfone, n =100). Patient survival was 29% (PAN) and 27% (polysulfone). In multivariate analysis, APACHE II score, inotrope requirement, and liver failure were significant determinants of survival. In conclusion, PAN and polysulfone membranes were not different with respect to hypotensive reactions or survival in critically ill patients undergoing continuous venovenous hemodialysis.
Spontaneous Gas Bubbling in Microporous Oxygenators
Authors: Karichev Zia R. , Muler Alexander L. , Vishnevsky Michael E.
Published: March 2003

Abstract: During operation of the microporous membrane oxygenators at some conditions, gas microbubbles penetrate into the blood. This effect, so‐called spontaneous bubbling, takes place even when the blood pressure is higher than the gas pressure. This phenomenon was confirmed experimentally both in a model cell with hydrophobic microporous hollow fibers being used in the oxygenators and in in vitro tests on the actual microporous hollow fiber oxygenator. We proposed a mechanism of spontaneous gas bubbling into liquid that contains dissolved gases. Because of a partial pressure gradient, the dissolved gases and water vapors are transported from blood into the gas pore. This causes Stefans gas flow directed from the liquid‐gas interface. Because of the high hydraulic resistance of the micropores, gas pressure at the meniscus increases up to gas bubbling. A mishandled priming of the oxygenator as well as the blood pressure pulsation caused by the roller pump operation contribute to spontaneous gas bubbling in the microporous oxygenators. The flow and pressure in the hydrophobic pores were calculated for various gases.
Influence on Blood of Plasticized Polyvinyl Chloride: Significance of the Plasticizer
Authors: Zhao Xiaobin , Courtney James M.
Published: March 2003

An investigation has been made of the significance of the level of the plasticizer di‐(2‐ethylhexyl)‐phthalate at the surface of plasticized polyvinyl chloride for interactions with blood components. Plasticized polyvinyl chloride before and after treatment with methanol to reduce the plasticizer surface level was assessed in terms of fibrinogen and albumin adsorption with unplasticized polyvinyl chloride acting as a control. As the plasticizer surface level decreased, fibrinogen adsorption decreased almost linearly while albumin adsorption increased initially before decreasing slightly. The investigation indicates that reduction in the amount of plasticizer at the surface improves the blood compatibility of plasticized polyvinyl chloride, and the influence on blood is due primarily to the plasticizer rather than the polyvinyl chloride itself.
Chaotic Dynamics in Circulation with Tohoku University Vibrating Flow Pump
Authors: Nitta Shin‐ichi , Yambe Tomoyuki , Kobayashi Shin‐ichi , Hashimoto Hiroyuki , Yoshizawa Makoto , Mastuki Hidetoshi , Tabayashi Kou‐ichi , Takeda Hiroshi
Published: March 2003

For the development of a totally implantable ventricular assist system (VAS), we have been developing the vibrating flow pump (VFP), which can generate oscillated blood flow with a relative high frequency (10–50 Hz) for a totally implantable system. In this study, the effects of left ventricular assistance with this unique oscillated blood flow were analyzed by the use of nonlinear mathematics for evaluation as the whole circulatory regulatory system, not as the decomposed parts of the system. Left heart bypasses using the VFP from the left atrium to the descending aorta were performed in chronic animal experiments using healthy adult goats. The ECG, arterial blood pressure, VFP pump flow, and the flow of the descending aorta were recorded in the data recorder during awake conditions and analyzed in a personal computer system through an A–D convertor. By the use of nonlinear mathematics, time series data were embedded into the phase space, the Lyapunov numerical method, fractal dimension analysis, and power spectrum analysis were performed to evaluate nonlinear dynamics. During left ventricular assistance with the VFP, Mayer wave fluctuations were decreased in the power spectrum, the fractal dimension of the hemodynamics was significantly decreased, and peripheral vascular resistance was significantly decreased. These results suggest that nonlinear dynamics, which mediate the cardiovascular dynamics, may be affected during left ventricular (LV) bypass with oscillated flow. The decreased power of the Mayer wave in the spectrum caused the limit cycle attractor of the hemodynamics and decreased peripheral resistance. Decreased sympathetic discharges may be the origin of the decreased Mayer wave and fractal dimension. These nonlinear dynamic analyses may be useful to design optimal VAS control.
Stability and Velocity in Incomplete Spinal Cord Injured Subject Gaits
Authors: Karčnik Tomaž , Kralj Alojz
Published: March 2003

We have defined 2 indices describing gait kinematic and dynamic stability. We assessed their values in the gaits of 5 different paraparetic subjects. The indices are correlated to the gait velocity to prove the close relationship between overall gate velocity and stability. Based on stability analysis and certain kinematic parameters, some possible ways of increasing the average gait velocity are explained.
Detection of the Cardiac Function by Fractal Dimension Analysis
Authors: Yambe Tomoyuki , Nanka Shun‐suke , Kobayashi Shin‐ichi , Tanaka Akira , Owada Naoki , Yoshizawa Makoto , Abe Ken‐ichi , Tabayashi Kouichi , Takeda Hiroshi , Nishihira Tetsuro , Nitta Shin‐ichi
Published: March 2003

Nonlinearity in circulation control attracts attention because nonlinearity is thought to be essential in the function of the living body. Many investigators have pointed out that the analysis of heart rate variability in particular is important in the analysis of autonomic nerve and cardiac function evaluation. Heart rate variability shows nonlinear behavior. However, until the present, many reports have been premised on linearity; linear correlation by frequency analysis has been used by many studies. However, in terms of this methodology, there is a problem applying it to the nonlinear living body. Therefore, fractal and chaos methodology has been used. The ascertainment of cardiac function has become important in allowing the clinical stage of a ventricular assist system to be successful. The purpose of this study was cardiac function evaluation by a methodology that was premised on nonlinearity. Chaos and fractal theory was used as a nonlinear dynamic theory. As a methodology of measurement, the volume of the left ventricle was used rather than an electrocardiogram, the waveform of arterial blood pressure. The volume was measured using acoustic quantification (AQ) ultrasonic echocardiography. Using these methodologies, the time series of many patients were analyzed. For example, drug administration was attempted in this study, and it was found that some drugs like ACE inhibitors showed a significant effect upon nonlinear dynamics in the cardiovascular system. The result, which attempted cardiac function evaluation by these various methodologies, is reported.
Modeling Lipid Uptake in Expanded Polytetrafluoroethylene Vascular Prostheses and Its Effects on Mechanical Properties
Authors: Mantovani Diego , Vermette Patrick , Fiset Michel , Guidoin Robert , Laroche Gaétan
Published: March 2003

Abstract: The radial transport across the wall of expanded polytetrafluoroethylene (ePTFE) arterial prostheses has a significant effect on lipid uptake observed in prostheses implanted in humans, which has been postulated to be one of the causes associated with implant failure. The goal of this study was to stimulate radial transport on a lipidic dispersion across the wall of an ePTFE prosthesis and investigate its effects on the circumferential mechanical properties of the prosthesis. An in vitro model was developed to simulate the lipidic radial transport across the wall. Lipids contained in a phosphatidylcholine dispersion were used as the transported molecules. Lipid concentration profiles were obtained after exposing commercial ePTFE prostheses to various transmural pressure and/or lipidic concentration gradients. Phospholipids gradually accumulated up to the external reinforcing wrap of the prosthesis, which clearly acted as a rigid barrier against lipid infiltration. Tensile tests performed on the virgin samples showed that the wrap was much more rigid than the microporous part of the prosthesis. After the lipid simulation, the rigidity of the wrap decreased with respect to what was observed for the virgin prosthesis. Finally, some clinical implications of this phenomena are discussed.
Vitamin E Modified Cellulose Membrane
Authors: Sasaki Masatomi , Hosoya Noriyuki , Saruhashi Makoto
Published: March 2003

Abstract: There has been a demand for hemodialysis membranes of better biocompatibility, the use of which would reduce the incidence of complications in patients who have been under long hemodialysis treatment. We developed a surface modification technique consisting of forming efficiently a synthetic polymer layer on the inside of the regenerated cellulose hollow fiber without impairing fiber performance. Our newly developed membrane has excellent biocompatibility by modifying the inner surface and by immobilizing vitamin E (α‐tocopherol), which serves as an antioxidant, to the modified surface.
Novel Online Infusate‐Assisted Dialysis System Performs Microbiologically Safely
Authors: Weber Christoph , Groetsch Wolfgang , Schlotter Sandra , Mitteregger Regina , Falkenhagen Dieter
Published: March 2003

Abstract: Administration of adequate amounts of commercial infusion fluids renders modern convective dialysis modalities, such as hemodiafiltration, labor‐intensive and costly. Preparation of infusate by cold sterilization of dialysis fluid, which is abundantly available, and its immediate (online) use, in contrast, enables a large volume fluid exchange in a cost‐effective manner. Recent developments aimed at more hygienic and user‐friendly online systems with increased operational flexibility. As a result the novel ONLINEplus system does not only provide online prepared infusate for convective dialysis therapy, but also for priming and rinsing of the extracorporeal blood circuit, for intradialytic bolus administration, and for re‐infusion of patients' blood as well. Production of infusate from potentially impure dialysis fluid containing endotoxins and other pyrogens raises severe concerns of affecting the patients' well‐being. To assess its safety, the online system was challenged with microbially contaminated dialysis fluid. Despite high levels of microbial counts (7.5 × 104± 105 CFU/ml), endotoxin concentration (14.1 ± 7.7 IU/ml and 9.265 ± 3.000 IU/ml, as measured turbidimetrically and chromogenically, respectively) and cytokine‐inducing activity (20,827 ± 3,082 pg IL‐1Ra/Mio WBC), we failed to detect contaminants in the final infusate during a 5 week laboratory testing period. In addition, infusate samples complied consistently with the European Pharmacopeia test for sterility. The present online system is comprehensive, operates user‐friendly, and provides microbiologically safe infusate in large quantities. In this way, both patients and dialysis staff will benefit from improved dialysis therapy and reduced treatment‐related labor burden, respectively. Moreover, convective dialysis modalities will become less expensive.
Tracing an Unhandled Suspect Lesion Through a Gamma Probe
Authors: Dâmaso R.S. , Zagury M.S. , De Campos T.P.R.
Published: March 2003

Abstract: This article describes the efforts of the authors in developing a handheld gamma detection probe and addresses a tentative surgical protocol for tracing an unhandled suspect lesion through an albumine‐aggregate 99Tcm tracer operative mapping. The electronic and software design for the system is discussed as well as its electronic and nuclear calibration. A phantom model mimicking a breast was built in order to help in the calibration of the system. Earliest results in an external detection procedure using the model and a 0.3 ml tracer sample (7 MBq activity) are presented.
Development of Anthropomorphic Upper Limb Prostheses with Human‐like Interphalangian and Interdigital Couplings
Authors: Da Cunha Fransérgio Leite , Schneebeli Hans‐Jörg Andreas , Dynnikov Vladimir Ivanovitch
Published: March 2003

Abstract: This article presents a model for the couplings of the movements between the phalanges and fingers in a hand when they execute certain functions. It also shows the importance of knowing these couplings, suggests methods for obtaining them, and discusses how to apply them to the construction of artificial upper limbs, highlighting the important mechanical aspects for achieving such a goal. Thus, it gives support for projects of upper limb prosthesis with anthropomorphic characteristics.
Pathological Mineralizations: Calcifications and Si‐Bearing Particles in Soft Tissues and Their Eventual Relationship to Different Prostheses
Authors: Leyva Ana Gabriela , Maguid Sandra Liliana , Rodriguez de Benyacar Maria Angelica , Lazaro Maria Alicia , Cocco Jose Maldonado , Citera Gustavo
Published: March 2003

Abstract: Polarizing microscopy (PM), scanning electron microscopy (SEM), x‐ray dispersive analysis (EDAX), x‐ray diffraction (XRD), and infrared spectrometry (IR) were used to study the following pathological mineralizations: calcifications and silicon(Si)‐bearing mineralizations in cerebral tissue from an epileptic child; traces of Si‐bearing particles in periprosthesic mammarian tissue, and calcifications in capsular mammarian tissue from a patient with a silicone gel mammarian implant, and 2 calcium‐bearing compounds, a typical apatitic calcification, and a nonphosphorous‐bearing calcification in arterial tissues. In this tissue we also found Si‐bearing particles due to an artifact from glassware.
Importance of Uniform Heparin Coating on Biopolymers
Authors: Da Luz Moreira Patrícia , Wada Maria Lucia Furlan , Novello Waldyr P.
Published: March 2003

Abstract: Cardiopulmonary surgeries need connectors for extracorporeal circulation. The patient's blood in contact with the tube surfaces modifies its plasmatic proteins, promotes platelet aggregation, and activates the complement system, unleashing thrombus formation. Thus, it becomes necessary for an anticoagulant to keep the circuit free from these events. Heparin is the anticoagulant used even after reports about its disadvantages. Platelet adherence seems to be very dependent on the quality from the surfaces that can promote cellular proliferation, aggregation, and thrombosis. In this study, we compare the quality of the heparin‐coated and uncoated surfaces. We used a blood cell culture and scanning electron microscopy (SEM) to visualize the platelet aggregation. It was concluded that there are groove areas that permit platelet adherence, and if they are not coated totally by the heparin, aggregation still occurs although in lower scale than on the uncoated tubes.
Electrolyzed Strong Acid Aqueous Solution Irrigation Promotes Wound Healing in a Burn Wound Model
Authors: Nakae Hajime , Inaba Hideo
Published: March 2003

Abstract: The purpose of the study was to understand the effectiveness of electrolyzed strong acid aqueous solution (ESAAS) for acceleration of epithelialization in a rat burn wound model. Eighteen anesthetized Sprague‐Dawley rats received 30% total body surface area third‐degree burns, and 2 days after injury, the wound eschars were removed. Rats were divided into 3 groups: Group 1, no irrigation; Group 2, irrigation with physiological saline; and Group 3, irrigation with ESAAS. Wounds were observed macroscopically until they were fully epithelialized, and epithelialized wounds were examined microscopically. Epithelialization of the wounds occurred significantly early in the rats treated with ESAAS (p < 0.05). Proliferation of associated lymphocytes and macrophages was more extensive in all rats that underwent irrigation than it was in control rats. ESAAS irrigation may promote tissue growth in burn wounds.
Ex Vivo Biocompatibility of Avidin‐Agarose: A New Device for Direct Adsorption of Biotinylated Antibodies from Human Whole Blood
Authors: Bosch T. , Lennertz A. , Duhr C. , Fink E. , Samtleben W.
Published: March 2003

Abstract: Radioimmunotherapy using radiolabeled antitumor antibodies (RAA) is limited by the toxicity of unbound antibodies in the circulation. Removal of excessive antibodies by affinity‐adsorption could therefore allow the administration of increased dosages of RAA while decreasing their adverse effects. Recently, avidin‐agarose (AA) minicolumns were used in animal experiments for the removal of biotinylated antibodies from whole blood exploiting the high affinity binding of biotin to avidin (pK 1015 M−1). This study was performed to evaluate the ex vivo biocompatibility of AA minicolumns with human blood. Ten ml AA minicolumns were perfused online ex vivo in the single pass mode with fresh blood from 8 healthy donors at a flow rate of 6.25 ml/min. The anticoagulation consisted of 0.5 IU heparin plus 0.0–2.1 mg citrate per ml of blood. In Part 1 of the study (40 min perfusion, n = 4), the optimal anticoagulation was found to be 0.5 IU heparin plus about 1 mg citrate per ml of blood. In Part 2 of the study, four 80 min test‐runs were performed. No signs of hemolysis were found, and the thrombogenicity of the AA gel was negligible. Cell counts and column inlet pressures remained constant; toward the end of the 80 min test‐runs, some activation of blood cells (elastase, β‐thromboglobulin), the complement system (C3a, C5a) and the plasmatic coagulation (thrombin‐antithrombin complex) was detectable. A moderate initial bradykinin release rapidly subsided to very low levels. In summary, AA minicolumns showed good biocompatibility upon contact with human whole blood and merit further investigation in a closed‐loop system for a potential application of direct tumor antibody removal by hemoperfusion.
Effects of Reduced Pulse Pressure to the Cerebral Metabolism During Prolonged Nonpulsatile Left Heart Bypass
Authors: Nishinaka Tomohiro , Tatsumi Eisuke , Nishimura Takashi , Taenaka Yoshiyuki , Imada Kyoko , Takano Hisateru , Koyanagi Hitoshi
Published: March 2003

Abstract: We investigated changes in the cerebral metabolism with long‐term reduced pulse pressure. Nine goats underwent pulsatile left heart bypass (LHB) for 2 weeks while awake, and nonpulsatile LHB was subsequently conducted for 4 weeks. The average pulse pressure during nonpulsatile LHB (13, 10, 11, and 11 mm Hg at the 1st, 2nd, 3rd, and 4th nonpulsatile LHB week, respectively) was significantly lower than that during pulsatile LHB (36 mm Hg). There were no significant differences in either arterio‐jugular venous oxygen differences (AJDO2) and cerebral oxygen extraction ratio between the 2nd pulsatile LHB week and the 1st, 2nd, 3rd, and 4th nonpulsatile LHB weeks. The arterio‐jugular venous glucose differences, jugular venous‐arterial lactate differences (JAD Lactate), and lactate oxygen indexes (JAD Lactate/AJDO2) also remained unchanged during the entire course of the experiments. In conclusion, the cerebral metabolism during nonpulsatile LHB did not change compared to that during pulsatile LHB.
Totally Implantable Ventricular Assist System that Can Increase Brain Blood Flow
Authors: Yambe Tomoyuki , Owada Naoki , Kobayashi Shin‐ichi , Tanaka Akira , Yoshizawa Makoto , Abe Ken‐ichi , Tabayashi Kouichi , Takeda Hiroshi , Hashimoto Hiroyuki , Nitta Shin‐ichi
Published: March 2003

Abstract: In the clinical usage of the ventricular assist device (VAD), multiple organ failure becomes an important problem. To improve the clinical record of the VAD, another organ function may be vitally important. For that reason, we have been developing a VAD system aiming at improving another organ's function. Development of the vibrating flow pump (VFP), which can generate a very unique flow pattern from 10 Hz to 50 Hz, was ongoing in our Institute. In order to evaluate brain blood flow and oxygen consumption, HbO2 was measured with a NIRO monitoring device in healthy adult goats. Four goats were anesthetized with halothane inhalation; then left thoracotomy was performed for the left heart bypass. HbO2 of the brain was measured by recording of the hemodynamic variables during left heart assistance with the VFP system. During left heart bypass with the VFP system, hemodynamic parameters stayed within normal range, and satisfactory pump output was easily obtained. Pump output stayed within 20–40% bypass to evaluate the effect of high frequency oscillated assist flow on brain blood flow during the same cardiac output. Interesting results were observed during the experiments. During 30 Hz drive of the VFP left heart assistance, HbO2 suggested that brain blood flow significantly increased compared with another drive frequency assistance during the same total cardiac output. These results suggest that we can control the brain blood flow with a totally implantable VAD system such as the VFP system.
A New Intracardiac Microaxial Pump: First Results of a Multicenter Study
Authors: Autschbach R. , Rauch T. , Engel M. , Brose S. , Ullmann C. , Diegeler A. , Mohr F.W.
Published: March 2003

Abstract: As coronary artery bypass grafting (CABG) surgery in the beating heart technique is progressing, new devices have been developed to overcome hemodynamic instabilities while tilting the heart for exposure of back wall vessels. A new device for in heart biventricular intracorporeal circulation was applied in 42 patients undergoing CABG surgery (Group 1). The control group consisted of 38 patients operated on using a conventional cardiopulmonary bypass setup (Group 2). The study protocol of the prospective, randomized multicenter study was approved by the local ethics committees. Patients were included following inclusion criteria and patient informed consent. Mean age, procedure time, mean arterial pressure (MAP), and hemolysis by means of plasma free hemoglobin (fHb) were assessed preoperatively, perioperatively, on postoperative Days 1 to 3, at discharge, and at a 3 month follow‐up. The mean age was 62.1 (range 59–74) years (Group 1), 62.7 (range 48–72) years (Group 2); procedure time was 112 min ± 31.9 min (Group 1), 137.4 min ± 36.2 min (Group 2); and 2.3 ± 0.6 (Group 1), 2.2 ± 0.7 (Group 2), vessels were revascularized. The flow on pump was 3.7 (2.5/4.4) L/min (Group 1), 4.9 (3.6/6.2) L/min (Group 2) which resulted in a MAP of 69.8 (4.0/143) mm Hg (Group 1), 58.3 (5.3/94) mm Hg while assessing the vessels of the back wall. Hemolysis defined by fHB was lower than 20 mg/dl at all times pre‐ and postoperatively. Intraoperative maximum values were up to 100 mg/dl in 4 patients (2 in Group 1 and 2 in Group 2). Body mass index was 26.4 ± 2.6 (Group 1), 27.9 ± 3.2. New York Heart Association Class was II to III in both groups. There were no pump related life threatening or severe adverse events. Beating heart procedures with ICC can be reliably and safely achieved. As the device is easy to use, it may deserve a more widespread use in the future.
Progress and Future Perspectives in Mechanical Circulatory Support
Authors: Sezai Yukiyasu
Published: March 2003

Abstract: Progress in several types of artificial organs in the cardiovascular field has significantly contributed to advancements in cardiac surgery. Due to the progress of high technology in fields other than medicine, both cardiac surgery and artificial organs have shown rapid and remarkable advances. In recent years, several types of blood pumps have been developed that are widely used not only as the main pump of cardiopulmonary bypass but also for circulatory support of postcardiotomy cardiogenic shock. In this article, the progress and current status of percutaneous cardiopulmonary support systems and ventricular assist devices (VADs) are described. In addition, new centrifugal and axial pumps, which are compact and implantable clinical use devices, are introduced. I believe that by making developments toward the clinical application of artificial hearts or VADs, not only in Japan but also in cooperation with colleagues at various institutions throughout the world, we will be able to make some contributions to the progress in the field of cardiac surgery. In the 20th century, medical research showed remarkable advances, mainly in medical electronics and pathophysiology. However, in the next century, we have to focus on other research fields, namely artifical organs and gene technology.
An In Vitro Methodology for Evaluating the Mechanical Properties of Aortic Vascular Prostheses
Authors: Quaglini Virginio , Villa Tomaso , Migliavacca Francesco , Carmo Michele , Settembrini Piergiorgio , Contro Roberto , Pietrabissa Riccardo
Published: March 2003

Abstract: The main problem in the replacement of pathological segments of the aorta with vascular prostheses consists of matching the fluid admittance of the host artery and the graft. This mismatch results from the different compliance between natural and prosthetic vessels and from the plastic dilatation of the prosthesis diameter that occurs after implantation. An experimental procedure was set up for evaluating the mechanical properties of aortic vascular prostheses. An MTS 858 MiniBionix testing machine was equipped with a purposely designed testing apparatus, which allows loading a ring‐shaped prosthesis specimen with forces that can be related easily to the transmural pressure acting on the prostheses in vivo. The reference pressure waveforms are simulated from a lumped parameter model of the cardiovascular system. Preliminary tests on 3 different (woven, warp knitted, and carbon‐coated warp knitted fabric) aortic prostheses point out a good reproducibility of the results. The fabric strongly affects the circumferential elasticity and the dimensional stability of the graft. Simulation of hypertension promotes larger diameter dilatation and reduction in compliance. Agreement between in vitro and clinical diameter measurements has been assessed for 8 prosthesis samples and found to be adequate. This method is thus a potentially useful means for preclinical evaluation of compliance of vascular prostheses for the purpose of matching to native vessels.
Laminin Modified Infection‐Preventing Collagen Membrane Containing Silver Sulfadiazine–Hyaluronan Microparticles
Authors: Lee Jong‐Eun , Park Jong‐Chul , Lee Kwang Hoon , Oh Sang Ho , Suh Hwal
Published: March 2003

Abstract: The newly developed laminin modified infection‐preventing collagen membrane consists of a 3 component laminate, comprising 2 outer collagen layers and a central laminin layer. The 2 outer collagen layers (dense and porous layers) were fabricated by air‐drying and freeze drying, respectively, and the laminin layer was formed by a straightforward liquid coating method. In addition, hyaluronan based microparticles containing silver sulfadiazine (AgSD) were incorporated into the 2 collagen layers (AgSD content 50 μg/cm2). Laminin coated collagen surfaces did not promote fibroblast attachment but showed a retarded fibroblast proliferation rate and an increased rate of collagen synthesis versus pure collagen surfaces. In an animal study, a laminin coating on a nonmedicated collagen membrane significantly increased both wound size reduction and vessel proliferation 7 days after application versus polyurethane film. Interestingly, the laminin coated AgSD medicated collagen membrane demonstrated higher wound size reduction and vessel proliferation and lower inflammation than the polyurethane control, suggesting that the laminin AgSD medicated collagen membrane substantially improves dermal wound healing.
Preliminary In Vivo Study of an Intra‐Aortic Impeller Pump Driven by an Extracorporeal Whirling Magnet
Authors: Li Guorong , Zhao Hong , Zhu Xiaodong , Ren Bing
Published: March 2003

Abstract: To achieve the aim of long‐term heart‐assist with a simple implantable device, we have been trying to develop a minimal intra‐aortic impeller blood pump driven by an extracorporeal magnetic device. The purpose of the current study was to evaluate its feasibility by acute in vivo animal tests. The minimal intra‐aortic pump was a cage‐supported rotor‐impeller, 17 mm in diameter with a total length of 30 mm. The driving magnet, mounted extracorporeally, was 55 mm in diameter and 50 mm in length. Seventeen dogs weighing from 28–34 kg were used in the study. After thoracic incision, heparin (50 U/kg) was infused. The impeller pump was inserted into the aortic chamber via a prosthetic vessel and fastened. Thin tubes were inserted into the left ventricular apex and the femoral artery to monitor the left ventricular (LV) and the aortic pressure. After closing the thoracic cavity, the extracorporeal whirling magnet, turned by an electric motor, was placed tightly against the thoracic wall parallel to the intra‐aortic pump. The experiments, each lasting for about 40 min, were successful in 7 animals; the other 10 animals died of bleeding during pump implantation and were excluded from the experiment. The peak systolic pressure of the left ventricle could be considerably decreased by the pump and was reduced to as low as 28 mm Hg at a rotational speed of 9,000 rpm, showing that the simple intra‐aortic impeller was effective in unloading the natural heart. The novel left ventricular assist device (LVAD) concept of an intra‐aortic impeller pump, driven by an extracorporeal magnetic device, is feasible.
On‐Line Parameter Identification of Systemic Circulation Using the Delta Operator
Authors: Kosaka Ryo , Sankai Yoshiyuki , Jikuya Tomoaki , Yamane Takashi , Tsutsui Tatsuo
Published: March 2003

Abstract: To develop effective medical care with the artificial heart, we propose a new method, on‐line parameter identification of the systemic circulation using the delta operator which can calculate the time‐varying and unmeasured hemodynamics of the internal human body from some measured data: aortic pressure and total flow in real time. This method consists of first, a dynamic physiological model which is configured with the physiological parameters Ca (aortic compliance) and Rp (total peripheral resistance); and second, a system identification method using the delta operator. In the computer simulation study, we could confirm the effectiveness to identify the physiological parameters. In animal experiments with a left ventricular assist system, the physiological parameters, Ca = 1.8 (ml/mm Hg) and Rp = 0.8 (mm Hg s/ml), could be identified on‐line.
Transcutaneous Functional Electrical Stimulator “Compex Motion”
Authors: Keller Thierry , Popovic Milos R. , Pappas Ion P.I. , Müller Pierre‐Yves
Published: March 2003

Abstract: Research groups in the field of functional electrical stimulation (FES) are often confronted with the fact that existing and commercially available FES stimulators do not provide sufficient flexibility and cannot be used to perform different FES tasks. The lack of flexibility of the commercial systems until now forced various FES research teams to develop their own stimulators. This paper presents a newly developed firmware and graphical programming software for the commercial Compex 2 stimulator which enhances the versatility and capabilities of the stimulator from a medical and therapeutic device to a neuroprosthesis and research tool. The new stimulator, called Compex Motion, can now be used to develop various custom‐made neuroprostheses, neurological assessment devices, muscle exercise systems, and experimental setups for physiological studies. It can be programmed to generate any arbitrary stimulation sequence that can be controlled or regulated by various external sensors, sensory systems, or laboratory equipment. By interconnecting two or more Compex Motion stimulators, the number of stimulation channels can be increased to multiples of four channels, 8, 12, 16, 20, and so forth. The stimulation sequences and the control strategies are programmed and stored on exchangeable credit card‐sized memory chip cards. The stimulator has four biphasic current‐regulated stimulation channels and two general purpose analog input channels that can be configured to measure the output voltage of a variety of sensors such as goniometers, inclinometers, gyroscopes, or electromyographic (EMG) sensors. For real‐time EMG control of the stimulation patterns, an EMG processing algorithm with software stimulation artifact blanking was implemented. The Compex Motion stimulator is manufactured by the Swiss company Compex SA and is currently undergoing clinical trials.
The Vienna Functional Electrical Stimulation System for Restoration of Walking Functions in Spastic Paraplegia
Authors: Bijak Manfred , Mayr Winfried , Rakos Monika , Hofer Christian , Lanmüller Hermann , Rafolt Dietmar , Reichel Martin , Sauermann Stefan , Schmutterer Christoph , Unger Ewald , Russold Michael , Kern Helmut
Published: March 2003

Abstract: An eight‐channel stimulation system, currently intended for stimulation of lower extremities, was developed and is introduced. The major development goals were easy handling, modularity to make the system easily adaptable for other functional electrical stimulation (FES) applications, and a wide stimulation parameter range for application‐specific parameter optimization. For paraplegic stepping, the system worn by the patient consists of 2 four‐channel stimulation modules, a central unit holding the battery and circuitry for power management and communication control, a wireless remote control unit, and a palmtop computer as the main control and input device. A software package for Microsoft Windows supports the design and optimization of stimulation sequences in the rehabilitation center. First tests with patients familiar with FES showed smoother movements during stepping and acceptable good handling. In combination with the PC software, the required stimulation sequences could be created in a very short time.
Stimulation of Nerves Innervating the Dog's Pancreas
Authors: Rozman Janez , Zorko Bojan , Bunc Matjaž , Žitko Mojca
Published: March 2003

Abstract: Our aim was to modulate secretion of insulin and glucagon into the blood of a diabetic but otherwise healthy dog with stimulation of nerves innervating the pancreas. The 33 electrode spiral cuffs were implanted in an adult beagle canine. The first cuff was installed on the vagus nerve, the second one on the splanchnic nerve, and the last one on the pancreatic nerve. To cause insulin‐dependent Type I diabetes, partial dysfunction of the pancreas was induced. Nerves were stimulated using biphasic, rectangular current pulses (10 mA, 200 μs, 20 Hz). Samples from the femoral artery were drawn before the experiment, after 5 min, and 5 min after the stimulation stopped. The results of radioimmunological assay of blood samples showed that in the intact pancreas, stimulation of the vagus nerve caused a considerable increase in insulin secretion, no significant change in glucagon secretion, and a decrease in C‐peptide secretion. Splanchnic nerve stimulation did not cause considerable change in insulin and C‐peptide secretion while considerable increase in glucagon secretion was noticed. Pancreatic nerve stimulation did not considerably change the secretion of any of the three hormones. In the dysfunctioned pancreas, vagal nerve stimulation caused an increase in insulin and glucagon secretion and a minor increase in C‐peptide secretion. Splanchnic nerve stimulation caused a minor decrease in insulin secretion, a considerable increase in glucagon secretion, and a small increase in C‐peptide secretion. Pancreatic nerve stimulation did not cause a considerable change in insulin secretion while a minor increase in glucagon and C‐peptide secretion was observed.
Short‐Term Result of Aortic Valve Replacement with Cryopreserved Homograft Valve in the University of Tokyo Tissue Bank
Authors: Motomura Noboru , Takamoto Shinichi , Murakawa Tomohiro , Yoneda Noriko , Shibusawa Sakiko , Maeda Katsuhide , Suematsu Yoshihiro , Murakami Arata , Nakajima Jun , Kotsuka Yutaka
Published: March 2003

Abstract: The short‐term results after aortic root replacement with 11 cryopreserved aortic homografts was examined. Since 1998, the University of Tokyo Tissue Bank has supplied 11 aortic homograft valves. Nine of the recipients were male, and the average age was 51.2 years. Nine out of 11 patients had suffered from a serious condition of native or prosthetic valve infectious endocarditis. All of the patients underwent aortic root replacement, and the blood type between the patient and the homograft was matched in 8 of the patients. Only 1 patient died (9.1%) in the short‐term due to sepsis. The preoperative degree of aortic valve regurgitation in all of the cases was third or fourth while the regurgitation disappeared after the operation in all of them. Thinking of the serious condition of our cases preoperatively, the 9.1% operative mortality was quite acceptable. Long‐term follow‐up is necessary to estimate the quality of the homografts.
Influence of St. Jude Medical Valve in Patients with Aortic Stenosis and Small Aortic Annulus on Cardiac Function and Late Survival Result
Authors: Natsuaki Masafumi , Itoh Tsuyoshi , Okazaki Yukio , Takarabe Kyoumi , Furukawa Koujirou , Rikitake Kazuhisa , Ohtubo Satoshi
Published: March 2003

Abstract: This clinical study analyzes our experience of postoperative cardiac function and long‐term survival rate in patients with aortic stenosis and small‐size St. Jude Medical (SJM) valve. Sixty‐eight patients who underwent aortic valve replacement by SJM valve were divided into two groups by preoperative aortic annulus diameter. Group 1 consisted of 44 patients with small aortic annulus and small‐size SJM valve (19 mm or 21 mm). In Group 1, small SJM standard valves were implanted in 16 patients, and small SJM Hemodynamic Plus (HP) valves were implanted in 28 patients. Group 2 consisted of 24 patients with large‐size SJM standard valve (23 mm or larger). Preoperative left ventricular mass index, left ventricular dimension, the dimension of ascending aorta, and body surface area were significantly smaller in Group 1 than in Group 2. Average age at surgery was older in Group 1 than in Group 2. Effective orifice area index of the SJM valve measured by the manufacturer's data was smaller in Group 1 than in Group 2. Postoperative left ventricular mass indexes of Group 1 (standard valve or HP valve) and Group 2 significantly decreased in comparison with the preoperative mass indexes. Postoperative left ventricular ejection fraction and the peak ejection rate of Group 1 were not different from those of Group 2. The 10 year survival rate of Group 1 was 79%, and the rate of Group 2 was 77%. At 10 years after surgery, freedom from valve‐related complication of Group 1 was 80%, and freedom from complication of Group 2 was 81%. Our results demonstrated that small‐size SJM valve afforded satisfactory long‐term survival rate and valve‐related event‐free rate for elderly patients with small body surface area and small aortic annulus.
A Novel, Valveless Ventricular Assist Device: The FishTail Pump. First Experimental In Vivo Studies
Authors: Feier Horea , Mekkaoui Choukri , Drevet Jean‐Baptiste , Sérée Yves , Richomme Claude , Rolland Pierre‐Henri , Mesana Thierry G.
Published: March 2003

Abstract: This article presents the first in vivo experiments with a new type of valveless ventricular assist device, a wave‐generating pump. Our goal was to evaluate the hemodynamic performance of the pump by comparing it with the Biomedicus BP‐80 centrifugal pump and by sustaining a 3 h long left ventricular assistance. We connected the two pumps in parallel and switched between them. We increased the aspiration by increments of –10 mm Hg at the inlet and measured developed flow, right carotid and femoral pressure, left atrial pressure, and left carotid flow. Then, we let the FishTail perform a 3 h long left ventricular assistance. The mean developed flow on the outlet was higher with the FishTail, with statistical significance, but this difference was not clinically significant. However, we observed an important amount of hemolysis during the ventricular assistance period. Although promising, this novel pumping device needs further prototypes to be clinically applicable.
Long‐Term Results of Valve Replacement with the CarboMedics Prosthetic Heart Valve
Authors: Onoda Koji , Suzuki Tomoaki , Kanemitsu Naoki , Yuasa Uhito , Takao Motoshi , Shimono Takatsugu , Tanaka Kuniyoshi , Shimpo Hideto , Yada Isao
Published: March 2003

Abstract: This study examined the long‐term results of the CarboMedics prosthetic heart valve. Between July 1990 and May 2000, 256 CarboMedics valve prostheses (120 single aortic, 62 single mitral, and 34 double aortic/mitral) were implanted into 216 patients (mean age 57.8 years). The mean follow‐up was 57.7 ± 36 months (maximum 133 months) with a total of 1,038.4 patient years. Patient survival, including operative deaths, was 85.1% at 10 years. Linearized rates for various complications were thromboembolism 0.39% per patient year, bleeding events 0.39% per patient year; prosthetic valve endocarditis 0.29% per patient year, nonstructural dysfunction 0.87% per patient year, and reoperation 0.39% per patient year. There were no valve thrombosis or structural valve failures in this series. The probabilities of freedom from thromboembolism and reoperation at 10 years were 96.3% and 93.1%, respectively. In conclusion, the CarboMedics valve can be used satisfactorily with a low incidence of thromboembolism and valve thrombosis.