Effect of Left Ventricular Assistance on Sympathetic Tone

To determine the effect of left ventricular assist device (LVAD) pumping on sympathetic tone, renal sympathetic nerve activity (RSNA) was detected in acute animal experiments.

Our TH-7B pneumatically driven, sac-type ventricular assist device was used in 7 adult mongrel dogs. RSNA was detected by the use of bipolar electrodes attached to the left renal sympathetic nerve. RSNA was amplified and integrated by use of an R-C integrator circuit. The area of the integrated nerve discharge per unit time was calculated in the computer system and expressed as RSNA per unit time.

During LVAD pumping, RSNA decreased with increase in blood pressure, with an increase in pulmonary artery flow, and with a decrease in left atrial pressure. These data suggest that LVAD has an effect on the sympathetic nervous system which is mediated by the aortic and cardiopulmonary baroreflex system.

Estimation of the following Cardiac Output Using Sympathetic Tone and Hemodynamics for the Control of a Total Artificial Heart

A sympathetic neurogram is potentially useful for the development of a real time total artificial heart (TAH) control system. We used sympathetic tone and hemodynamic derivatives to estimate the following cardiac output in acute animal experiments using adult mongrel dogs. Moving averages of the mean left atrial pressure and mean aortic pressure were used as parameters of the preload and afterload, respectively. Renal sympathetic nerve activity (RSNA) was employed as a parameter of sympathetic tone. Equations for the following cardiac output were calculated using multiple linear regression analysis of the time series data. A significant correlation was observed between the estimated and following measured cardiac output. These results suggest the potential usefulness of the sympathetic neurogram for the real time TAH automatic control system.

Vagal Nerve Activity and the High Frequency Peak of the Heart Rate Variability

For the Quality of life (QOL) of patients with an artificial heart system, monitoring an information of the cardiovascular control system may be important. We have been evaluating the autonomic nervous system for that purpose. Recently, fluctuations in hemodynamic parameters including heart rate variability (HRV) were evaluated by means of spectral analysis and nonlinear mathematical analysis. Respiratory wavers in HRV were thought ro reflect ongoing information of the parasympathetic nerve activity. Is it true? In order to confirm this hypothesis, we recorded vagal nerve activity directly in the chronic animal experiments. Six healthy adult goats were anesthetized with Halothene inhalation and thoracotomy were performed by the fourth lib resection during mechanical ventilation. Arterial blood pressure, right and left atrial pressures were continuously monitored with the catheter insertion. Cardiac output was measured by the electromagnetic flowmeter attached to the ascending aorta. After the chest was closed, incision was made to the left neck and left vagal nerve was separated. Stainless steel electrodes were inserted into the vagal nerve and fixed by the plasticizer. After the incision was closed, the goats were transferred to the cage and extubated after waking. Hemodynamic parameters and vagal nerve activity were measured in the awake condition. The results showed that clear observation of the autonomic nerve discharges were embodied by this experimental system. The vagal nerve discharges were synchronized with heart beat and respiration. The vagal nerve tonus was significantly influenced by the hemodynamic alteration. However in some condition, the respiratory wave was not always consistent with tonus of the vagal nerve activity, thus suggesting that we should check another information to evaluate the parasympathetic tone. We must continue this study to evaluate an autonomic nerve during artifical heart circulation.

Mayer Waves in Dogs with Total Artificial Heart

To assess the effect of a total artificial heart (TAH) on the autonomic nervous system a power spectral analysis of the hemodynamics in a TAH animal was done by the maximum entropy method. Two pneumatically driven sac-type ventricular assist devices were implanted as total biventricular bypass (BVB) in adult mongrel dogs to compare the differences between natural heart and TAH. Once the BVB was pumping, the natural heart was electrically fibrillated to constitute the BVB-type TAH model. In the arterial pressure waveform in animals with TAH, respiratory waves were not changed (97.7±24.6%) though Mayer waves were significantly decreased (47.5 ± 22.6%) compared with the animal with a natural heart. These results suggest that prosthetic hemodynamics in the TAH animal affect fluctuations in the cardiovascular system.

Monitoring System for the Totally Implantable Ventricular Assist System by Use of Sensors for Virtual Reality

For the development of the totally implantable artificial organs, it is an important problem to monitor the conditions of the implantable devices, especially when used in clinical cases. In this study, we used position sensors for the 3-dimensional (3-D) virtual reality (VR) system monitor an implantable artificial heart. The sensors used in the experiments were 3-space Fastrak (Polhemus, USA). The position sensors using electro-magnetic forces were attached to the inner actuating zone. Sensitivity of the position sensors was in the order of around 0.8 mm. By use of these VR position sensors, we could easily detect the six degrees of freedom as x,y,z, and pitch, yaw, roll of these sensors. Experimental evaluation using a model circulation loop and healthy adult goats was performed. Experimental results suggest that our newly developed implantable sensors for monitoring the implantable artificial heart system were useful for sensing driving condition, thus possibly useful for the implantable devices for clinical usage.

Development of Total Artificial Heart with Economical and Durability Advantages

To develop a total artificial heart (TAH) pump system, we created a design paying particular attention to durability and cost. We adopted a pneumatically driven sac type artificial heart, where the configuration of the sac was decided according to the methodology of flow visualization. Its configuration is almost round to achieve as little stagnation as possible and a low turbulent flow. The main body of the sac was made using polyvinyl chloride (PVC) paste. The paste was poured into an external mold, and heated in a hot air drying oven. Coating was performed using polyurethane. The basic performance of this pump system was tested using a model circulation circuit, and a fitting study through acute animal experiment, using a healthy adult goat, was carried out. As for the TAH produced experimentally, a pump output exceeding 5.0 l/min in the model circulation circuit was provided. Implantation in the internal pleural cavity of a healthy adult goat, 55 kg in weight, proved possible and quite easy in comparison. It is thought that a more refined design in the connector part is desirable. Furthermore, a chronic experiment with the TAH will be carried out, and examination will need to be repeated in the future.

Can the Artificial Heart Make the Circulation Become Fractal?

In order to analyze the hemodynamic parameters in prosthetic circulation as an entity and not as decomposed parts, non linear mathematical analyzing techniques, including the fractal dimension analyzing theory, were utilized. Two pneumatically actuated ventricular assist devices were implanted, as biventricular bypasses (BVB), in chronic animal experiments, using four healthy adult goats. For the comparison between the natural and prosthetic circulation in the same animals, the BVB type complete prosthetic circulation model with ventricular fibrillation, was adopted. All hemodynamic parameters with natural and prosthetic circulation were recorded under awake conditions, and calculated with a personal computer system. Using the non-linear mathematical technique, the arterial blood pressure waveform was embedded into the return map as the beat-to-beat time series data and fractal dimension analysis were performed to analyze the reconstructed attractor. By the use of the Box counting method, fractal dimension analysis of the hemodynamics was performed. Return map of the hemodynamics during natural and artificial circulation showed fractal characteristics, and fractal dimension analysis of the arterial blood pressure revealed the fact that lower dimensional fractal dynamics were evident during prosthetic circulation. Fractal time series data is suggested to have robustness and error resistance, thus our results suggest that the circulatory regulatory system with an artificial heart may have these desired characteristics.

Strange Hemodynamic Attractor Parameter with 1/R Total Artificial Heart Automatic Control Algorithm

To evaluate the automatic control algorithm of the total artificial heart (TAH) as an entity, and not just as parts, a non-linear mathematical analyzing technique including chaos theory was utilized. Chronic experiments on the biventricular bypass type artificial heart implantation were performed in healthy adult goats after the natural ventricles were removed. Hemodynamic time series data were recorded under the awake standing condition with TAH 1/R and fixed driving. Time series data were recorded on a magnetic tape and analyzed on a personal computer system with an A-D converter. Using the nonlinear mathematical technique, the time series data were embedded into the phase space and the Lyapunov numerical method was carried out for the quantitative evaluation of the sensitive dependence on the initial condition of the reconstructed attractor. Calculation of the largest Lyapunov exponents suggested that the reconstructed attractor of the left pump output during TAH 1/R control was a larger dimensional strange attractor, a characteristic pattern of deterministic chaos. A total system indicating chaotic dynamics was thought to be a flexible and intelligent control system. Thus, our results suggest that 1/R TAH control may be suitable for the biventricular assist type total artificial heart.

Development of Intracoronary Local Adhesive Delivery Technique

Acute coronary occlusion may occur in weak coronary atherosclerotic lesions, including dissection, ulceration or thrombus. In some cases of occlusion “bail-out” is performed by using recently developed New Devices. However, these have not yet completely solved the problem to this end, we designed a new method of coronary revascularization, the Intracoronary Local Adhesive Delivery Technique, utilizing antithrombotic and absorbable adhesive injected locally into the fragile and morbid arterial wall using a drug delivery PTCA catheter more flexible than the existing New Devices. This adhesive strengthened and hardened the lesions. In this study, we examined the efficacy of making an adhesive cylinder in arteries of similar size to the coronary, through acute animal experiments using the existing clinical adhesives and drug delivery PTCA catheters and 12 femoral arteries of adult goats. We were successful in forming firm tunnels along the inside of six arteries, infused with approximately 0.04 ml Cyanoacrylate. These tunnels were observed with intravascular ultrasound (IVUS) imaging and evaluated microscopically. These results suggest the feasibility of this method as a new approach for making synthetic resinous stents.

Peristaltic hemodynamics of a new pediatric circulatory assist system for Fontan circulation using shape memory alloy fibers

Fontan procedure is one of the common surgical treatments of congenital heart diseases. Patients with Fontan circulation have single ventricle in the systemic circulation with the total cavopulmonary connection. We have been developing a pulmonary circulatory assist device using shape memory alloy fibers for Fontan circulation with total cavopulmonary connection. It consisted of the shape memory alloy fibers, the diameter of which are 100 µm. The fibers could wrap the ePTFE conduit for Fontan TCPC connection from the outside. We designed the sequential motion control system for sophisticated pulmonary hemodynamics by the pulsatile flow generation. In order to achieve pulsatile flow assistance in pulmonary arterial system, we fabricated a mechanical structure by sequential contraction of shape memory alloy fibers. Then, we developed a sequential contraction controller for the assist system, which could reproduce the wall contractile velocity at 6.0 to 20.0 cm/sec. We examined hemodynamic characteristic of its function using a mock circulatory system, which consisted of two overflow tanks representing venous and pulmonary arterial pressures in Fontan circulation. As a result, the pulmonary circulation assist device with sequential contraction could achieve effective promotion of the pulsatility in pulmonary arterial flow.

Controlling methods of a newly developed extra aortic counter-pulsation device using shape memory alloy fibers

Diastolic counter-pulsation has been used to provide circulatory augmentation for short term cardiac support. The success of intra-aortic balloon pump (IABP) therapy has generated interest in long term counter-pulsation strategies to treat heart failure patients. The authors have been developing a totally implantable extra aortic pulsation device for the circulatory support of heart failure patients, using 150 µm Ni-Ti anisotropic shape memory alloy (SMA) fibers. These fibers contract by Joule heating with an electric current supply. The special features of our design are as follow: non blood contacting, extra aortic pulsation function synchronizing with the native heart, a wrapping mechanical structure for the aorta in order to achieve its assistance as the aortomyoplsty and the extra aortic balloon pump. The device consisted of rubber silicone wall plates, serially connected for radial contraction. We examined the contractile function of the device, as well as it controlling methods; the phase delay parameter and the pulse width modulation, in a systemic mock circulatory system, with a pneumatically driven silicone left ventricle model, arterial rubber tubing, a peripheral resistance unit, and a venous reservoir. The device was secured around the aortic tubing with a counter-pulsation mode of 1:4 against the heartbeat. Pressure and flow waveforms were measured at the aortic outflow, as well as its driving condition of the contraction phase width and the phase delay. The device achieved its variable phase control for co-pulsation or counter-pulsation modes by changing the phase delay of the SMA fibers. Peak diastolic pressure significantly augmented, mean flow increased (p<0.05) according to the pulse width modulation. Therefore the newly developed extra aortic counter-pulsation device using SMA fibers, through it controlling methods indicated its promising alternative extra aortic approach for non-blood contacting cardiovascular circulatory support.

Deep venous thrombosis among disaster shelter inhabitants following the March 2011 earthquake and tsunami in Japan: a descriptive study

Objectives

A retrospective analysis of data collected during subject screening following Japan's March 2011 earthquake and tsunami was performed. We aimed to determine the incidence of deep venous thrombosis (DVT) among screened subjects and to identify risk factors associated with the development of DVT as independent variables.

Methods

Calf ultrasonography was undertaken in 269 subjects living in 21 shelters in Miyagi prefecture during the one-month period immediately following the March 2011 disaster. Information regarding the health and risk factors of subjects was collected by questionnaire and assessment of physical signs.

Results

Of the 269 evacuees screened, 65 (24%) met the criteria for calf DVT. We found lower limb trauma, reduced frequency of urination and sleeping in a vehicle to be independent positive predictors of DVT.

Conclusions

Evacuees had an increased risk of developing DVT, associated with tsunami-related lower limb injury, immobility and dehydration.

Examination of mitral regurgitation with a goat heart model for the development of intelligent artificial papillary muscle

Annuloplasty for functional mitral or tricuspid regurgitation has been made for surgical restoration of valvular diseases. However, these major techniques may sometimes be ineffective because of chamber dilation and valve tethering. We have been developing a sophisticated intelligent artificial papillary muscle (PM) by using an anisotropic shape memory alloy fiber for an alternative surgical reconstruction of the continuity of the mitral structural apparatus and the left ventricular myocardium. This study exhibited the mitral regurgitation with regard to the reduction in the PM tension quantitatively with an originally developed ventricular simulator using isolated goat hearts for the sophisticated artificial PM. Aortic and mitral valves with left ventricular free wall portions of isolated goat hearts (n=9) were secured on the elastic plastic membrane and statically pressurized, which led to valvular leaflet-papillary muscle positional change and central mitral regurgitation. PMs were connected to the load cell, and the relationship between the tension of regurgitation and PM tension were measured. Then we connected the left ventricular specimen model to our hydraulic ventricular simulator and achieved hemodynamic simulation with the controlled tension of PMs.

A new control method depending on primary phase angle of transcutaneous energy transmission system for artificial heart

A new control method for stabilizing output voltage of the transcutaneous energy transmission system for artificial heart is proposed. This method is primary side, is outside of the body, which is not depending on a signal transmission system from the implanted device. The impedance observed from primary side changes from inductive to capacitive and the output voltage decreases drastically when the output current is large and the coupling factor is higher than that of the optimal condition. In this case, the driving frequency should be changed to higher so that the phase angle of the primary impedance is zero degree. The preliminary examination showed that this control method can enhance the output voltage limit to twice and the feasibility of the primary side control.

Template for preparation of papers for IEEE sponsored conferences & Symposia

Rotary blood pumps which have contact-less suspension are small, durable and widely used for left ventricular assist devices (LVADs). In order to design a total artificial heart (TAH) with rotary blood pumps, two pumps one for each ventricle, are controlled independently. Some of the challenges for the development of a TAH includes the requirement of a small size and the anatomical fitting of inlets and outlets which should be arranged closely on the circumference in the same direction. And they should be combined into a unit. In this paper, a helical flow total artificial heart (HFTAH) combing two centrifugal pumps with helical inlet in face is proposed in order to achieve a smaller TAH. To examine the pump performance, a preliminary test model for left ventricle was built, the size of the pump was 69.0mm in diameter and 45.0mm height. The size of the impeller was 44.0mm in diameter and 23.0mm height including a 15.0mm-height hydrodynamic bearing. The pump was externally driven by a direct current motor. 5.0L/min flow rate against 100mmHg pressure difference was obtained, where the total power consumption was 5.0W, the system efficiency was 23% with a rotational speed of 2070rpm. In this system, maximum pressure head, flow rate and efficiency were 420mmHg, 15.0L/min and 26%, respectively. In acute animal experiments with three healthy adult goats, the total biventricular bypass assist system using the pumps was able to maintain the maximum aortic flow at approximately 5.0L/min, and the pulmonary arterial flow at approximately 4.6L/min, the mean aorta pressure was 105mmHg, and the mean pulmonary artery pressure was 51mmHg. The development of the control method is undergoing, and a driving system and the pump aiming at the chronic animal experiments will be developed.

Structural design of a newly developed pediatric circulatory assist device for Fontan circulation by using shape memory alloy fiber

Total cavopulmonary connection (TCPC) is commonly applied for the surgical treatment of congenital heart disease such as single ventricle in pediatric patients. Patients with no ventricle in pulmonary circulation are treated along with Fontan algorithm, in which the systemic venous return is diverted directly to the pulmonary artery without passing through subpulmonary ventricle. In order to promote the pulmonary circulation after Fontan procedure, we developed a newly designed pulmonary circulatory assist device by using shape memory alloy fibers. We developed a pulmonary circulatory assist device as a non-blood contacting mechanical support system in pediatric patients with TCPC. The device has been designed to be installed like a cuff around the ePTFE TCPC conduit, which can contract from outside. We employed a covalent type functional anisotropic shape memory alloy fiber (Biometal, Toki Corporation, Tokyo Japan) as a servo actuator of the pulmonary circulatory assist device. The diameter of this fiber was 100 microns, and its contractile frequency was 2-3 Hz. Heat generation with electric current contracts these fibers and the conduit. The maximum contraction ratio of this fiber is about 7% in length. In order to extend its contractile ratio, we fabricated and installed mechanical structural units to control the length of fibers. In this study, we examined basic contractile functions of the device in the mock system. As a result, the internal pressure of the conduit increased to 63 mmHg by the mechanical contraction under the condition of 400 msec-current supply in the mock examination with the overflow tank of 10 mmHg loading.

Sensorless control for a sophisticated artificial myocardial contraction by using shape memory alloy fibre

The authors have been developing an artificial myocardium, which is capable of supporting natural contractile function from the outside of the ventricle. The system was originally designed by using sophisticated covalent shape memory alloy fibres, and the surface did not implicate blood compatibility. The purpose of our study on the development of artificial myocardium was to achieve the assistance of myocardial functional reproduction by the integrative small mechanical elements without sensors, so that the effective circulatory support could be accomplished. In this study, the authors fabricated the prototype artificial myocardial assist unit composed of the sophisticated shape memory alloy fibre (Biometal), the diameter of which was 100 microns, and examined the mechanical response by using pulse width modulation (PWM) control method in each unit. Prior to the evaluation of dynamic characteristics, the relationship between strain and electric resistance and also the initial response of each unit were obtained. The component for the PWM control was designed in order to regulate the myocardial contractile function, which consisted of an originally-designed RISC microcomputer with the input of displacement, and its output signal was controlled by pulse wave modulation method. As a result, the optimal PWM parameters were confirmed and the fibrous displacement was successfully regulated under the different heat transfer conditions simulating internal body temperature as well as bias tensile loading. Then it was indicated that this control theory might be applied for more sophisticated ventricular passive or active restraint by the artificial myocardium on physiological demand.

Assessment of synchronization measures for effective ventricular support by using the shape memory alloy fibred artificial myocardium in goats

Thromboembolic and haemorrhagic complications are the primary causes of mortality and morbidity in patients with artificial hearts, which are known to be induced by the interactions between blood flow and artificial material surfaces. The authors have been developing a new mechanical artificial myocardial assist device by using a sophisticated shape memory alloy fibre in order to achieve the mechanical cardiac support from outside of the heart without a direct blood contacting surface. The original material employed as the actuator of artificial myocardial assist devices was 100um fibred-shaped, which was composed of covalent and metallic bonding structure and designed to generate 4-7 % shortening by Joule heating induced by the electric current input. In this study, we focused on the synchronization of the actuator with native cardiac function, and the phase delay parameter was examined in animal experiments using Saanen goats. Total weight of the device including the actuator was around 150g, and the electric power was supplied transcutaneously. The device could be successfully installed into thoracic cavity, which was able to be girdling the left ventricle. The contraction of the device could be controlled by the originally designed microcomputer. The mechanical contraction signal input had been transmitted with the phase delay of 50-200 msec after the R-wave of ECG, and hemodynamic changes were investigated. Cardiac output and systolic left ventricular pressure were elevated with 20% delay of cardiac cycle by 27% and 7%, respectively, although there was smaller difference under the condition of the delay of over 30%. Therefore, it was suggested that the synchronization measures should be examined in order to achieve sophisticated ventricular passive/active support on physiological demand.

Fractal dimension of 40 MHz intravascular ultrasound radio frequency signals

OBJECTIVE

Fully automatic tissue characterization in intravascular ultrasound systems is still a challenge for the researchers. The present work aims to evaluate the feasibility of using the Higuchi fractal dimension of intravascular ultrasound radio frequency signals as a feature for tissue characterization.

METHODS

Fractal dimension images are generated based on the radio frequency signals obtained using mechanically rotating 40 MHz intravascular ultrasound catheter (Atlantis SR Plus, Boston Scientific, USA) and compared with the corresponding correlation images.

CONCLUSION

An inverse relation between the fractal dimension images and the correlation images was revealed indicating that the hard or slow moving tissues in the correlation image usually have low fractal dimension and vice-versa. Thus, the present study suggests that fractal dimension images may be used as a feature for intravascular ultrasound tissue characterization and present better resolution then the correlation images.

Development of an Artificial Myocardium using a Covalent Shape-memory Alloy Fiber and its Cardiovascular Diagnostic Response

The authors have been developing a newly-designed totally-implantable artificial myocardium using a covalent shape-memory alloy fibre (Biometal&#174;, Toki Corporation), which is attached onto the ventricular wall and is also capable of supporting the natural ventricular contraction. This mechanical system consists of a contraction assistive device, which is made of Ti-Ni alloy. And the phenomenon of the martensitic transformation of the alloy was employed to achieve the physiologic motion of the device. The diameter of the alloy wire could be selected from 45 to 250&#956;m. In this study, the basic characteristics of the fiber of 150&#956;m was examined to design the sophisticated mechano-electric myocardium. The stress generated by the fiber was 400gf under the pulsatile driving condition (0.4W, 1Hz). Therefore it was indicated that the effective assistance might be achieved by using the Biometal shape-memory alloy fiber.

An innovative approach to evaluate a cardiac function based on surface measurement

Major function of the heart is to pump blood flow up to all tissues or organs in the body, and it is generally recognized that cardiac function under various diseased conditions are mainly represented by a relationship between blood flow and pressure inside of the heart. In this report, an original proposal of evaluation method on cardiac function is introduced through a simultaneous measurement of various points of cardiac muscular surface. An optical three-dimensional location sensor was employed to measure a displacement change of anatomically specific points on heart surface. Then, changes in strain in each regional surface area were quantitatively obtained. This result indicated similar tendency obtained from echocardiogram. It was also indicated that there was a difference in displacements and phrases between control and arrhythmia. Moreover, strain change in regional area was coincident with a contraction of natural heart. It was found that an attempt to superimpose the data of strain change onto the video images of natural heart was extremely helpful to understand a cardiac function visually.

Dynamic response of the pulmonary circulation in continuous flow artificial heart systems

Pulmonary circulation dynamics is important when considering bi-ventricular assist devices (BiVAD) or total artificial heart (TAH) systems and in investigating the mechanism of atrial collapse in order to design better control algorithms. In this study, we investigated pulmonary circulation dynamics in a continuous flow artificial heart system by performing acute tests on a mature goat. By varying the right pump speed, we were able to observe the dynamic response of the left atrial pressure (LAP) and simulate conditions that result in atrial suction. The results showed a time constant characteristic of a compliance lag in LAP response to changes in right pump output in the TAH configuration. These results may prove useful in the design of a new mock circulatory system that incorporates the dynamics of the pulmonary circulation, and in the improvement of existing control algorithms that prevent atrial wall collapse.

Quantitative evaluation of the effect of visually-induced motion sickness using causal coherence function between blood pressure and heart rate

To evaluate the effect of visually-induced motion sickness on the human, blood pressure variability (BP) and heart rate variability (HR) of 51 normal subjects watching a 15min-long video image taken by a vibrating handy camera were analyzed. Not only coherence function (K/sup 2/) between BP and HR but also two causal coherence functions: K/sup 2//sub BP-->HR/ from BP to HR and K/sup 2//sub HR-->BP/ from HR to BP were introduced to divide causal linearity of the cardiovascular system regarded as a closed-loop system. K/sup 2/ represents total linearity of the system. K/sup 2//sub BP-->HR/ and K/sup 2//sub HR-->BP/ correspond to the baroreflex system and the mechanical hemodynamics, respectively. The results revealed that K/sup 2//sub BP-->HR/ at the Mayer wave-band (around 0.1 Hz) of the subjects prone to motion sickness decreased gradually and was significantly lower than that of the subjects not prone to in later scenes. This result has never been obtained from conventional methods dealing with a cardiovascular system as an open-loop system.

Effect of the alternative magnetic stimulation on peripheral circulation for regenerative medicine

Regenerative medicine for patients with peripheral atherosclerosis attracts considerable attention around the world. However, ethical problems persist in gene therapy. This study evaluates the effect of alterative magnetic stimulation on peripheral circulation. The effect of magnetic stimulation as a medical treatment was examined using a thermograph for 11 healthy volunteers. The thermograph was used to measure the rise in skin temperature. The experimental results suggested an improvement in the peripheral circulation. The results of our study suggest the effectiveness of alternative magnetic stimulation on atherosclerosis. We intend to extend our study in order to establish a methodology for regenerative medical treatment for patients with peripheral atherosclerosis. Further, we wish to advance the current research in the field of angiogenesis.

Cardio-ankle vascular index (CAVI) for the monitoring of the atherosclerosis after heart transplantation

Atherosclerosis has been reported to progress rapidly after heart transplantation. A quantitative diagnosis is required for the diagnosis of atherosclerosis after heart transplantation. In this study, we compared brachial-ankle pulse wave velocity (baPWV) and cardio-ankle vascular index (CAVI) for the diagnosis. The average values of both baPWV and CAVI in the seven cases after heart transplantation were found to be signif-icantly large in comparison to the average values of the normal healthy people of the same age group. When comparisons were made before and after the heart transplantation in a particular case, CAVI was stable and baPWV changed sharply. A lot of parameters such as blood pressure, blood volume, etc. have been reported to influence baPWV. The results of this study suggested that CAVI was a stable parameter in comparison to baPWV even after heart transplantation. Thus, CAVI may be useful in the diagnosis of arteriosclerosis after heart transplantation.

Chaos analysis of electro encephalography and control of seizure attack of epilepsy patients

In order to evaluate the EEG of patients with epilepsy, chaos analysis was performed for the subdural EEG time series data. The chaos attractor was reconstructed in the phase space and the correlation dimension. KS entropy calculated from the Lyapunov exponents was evaluated. Before the seizure attack, the KS entropy showed a lower value when compared with the time series data recorded during healthy condition. The results of our study suggest that it is possible to predict the seizure attack by the chaos analysis of the EEG signal. Further, we aim at developing an automatic control system for predicting a seizure attack by the use of local cooling of the focus with Peltier elements.

Miniature vibrating flow blood pump using a cross-slider mechanism for external shunt catheter

The prototype of the miniature vibrating flow pump (VFP) is developed for the external shunt catheter. The cross-slider mechanism is applied to vibrate the tube, which causes the pumping effect. This mechanism results in successful development of the miniature and lightweight VFP. By the use of the prototype VFP, the experiment of the basic pump performance is made in detail based on the authorized procedure in the research field of fluids engineering. The typical H-Q curve of VFP, which is the relationship between the pump head and the flow rate, can be obtained. This result suggests that the miniature VFP developed here can be expected to be used as the booster pump for the external shunt catheter in clinical applications.

Fluctuations of Emax of the left ventricle: effect of atrial natriuretic polypeptide

Recently the circadian rhythm of fluctuations in heart rate variability (HRV) has gained increasing attention, and the use of appropriate treatment corresponding to the circadian rhythm has become an important issue. However, the question has been raised as to whether the rhythm of fluctuation is only limited to HRV, and if a rhythm is also present in the contraction of the heart. The mathematical technique of electrical circuit simulation of the cardiovascular system was used to observe the Emax rhythm. In this study, the therapeutic effect of various drugs, including atrial natriuretic polypeptide (ANP), was confirmed. The effect of inotropic drugs including ANP on Emax was observed, and the results based on an old and a new method of determining Emax . were examined. Furthermore, the chaos analysis of Emax was also made. The time series of Emax showed an increased complexity due to the administration of ANP. In conclusion, it might be important to consider not only the fluctuation of HRV, but also an analysis of the fluctuation in the contraction of the heart.

[Relationship between depression and lipid metabolism in the elderly with hypertension]

In order to examine the relationship between depressive symptoms and the lipid metabolism in the elderly with hypertension, we recruited 311 outpatients aged 65 or older with hypertension and defined depression as patients with 6 or more symptoms on Geriatric Depression Scale short form. We further classified depressed patients into three groups: mild depressed with 6-7 symptoms, moderate depressed with 8-10 symptoms and severe depressed with 11 or more symptoms. Serum total cholesterol, serum HDL cholesterol and serum LDL cholesterol levels were significantly higher in female depressed patients than those in nondepressed patients (TC, 194.6 +/- 30.1 vs 208.0 +/- 32.8 p < 0.01; HDL, 67.3 +/- 19.3 vs 72.3 +/- 16.2 p < 0.01; LDL, 107.6 +/- 26.5 vs 116.0 +/- 29.1 p < 0.05). In male patients, serum lipids were not significantly associated with depressive symptoms but depressed patients were significantly older than nondepressed patients (75.3 +/- 6.2 vs 78.0 +/- 5.9 p < 0.05). Concerning the analysis of the severity of depression, serum total cholesterol and serum LDL cholesterol levels were significantly higher in mildly depressed patients than nondepressed patients in females and the same tendency was seen in male patients. No linear associations were shown between the severity of depression and serum lipids. We concluded that hyperlipidemia may be associated with depressive symptoms in elder patients with hypertension and that it might be related the severity of depression. We need to further investigate the relationship between depression and lipid metabolism in larger population samples.

Automatic monitoring system for artificial hearts using self organizing map

This study presents an automatic monitoring system for artificial hearts. The self organizing map (SOM) was applied to monitoring and analysis of an aortic pressure (AoP) signal measured from an adult goat equipped with a total artificial heart. In the proposed system, two different SOMs were used to detect and classify abnormalities in the measured AoP signal. In the first stage, an ordinary SOM, taught with only normal AoP data, was used for detection of abnormalities on the basis of the quantization error in the real-time monitoring task. In the second stage, a supervised SOM was used for classification of abnormalities. The supervised SOM can be regarded as an ordinary SOM with an extra class vector for solving the classification problem. The class vector is assigned to every node in the second SOM as an output weight learned according to Kohonen's learning rule. The effectiveness of detection and classification of abnormalities using these two SOMs was confirmed.

Recent progress on the vibrating flow pump as a totally implantable ventricular assist device

This study describes the present state of progress in the development of the vibrating flow pump (VFP) ventricular assist system. We have proceeded with development aiming at a totally implantable ventricular assist system with smaller size and lighter weight appropriate for Asians like the Japanese by increasing the drive frequency. An actuator is important for the development of the miniature sized and lightweight artificial heart. We applied a linear motor for the mechanical part at first. The step motor was applied after that. This form may be best if we want the lightweight small sized motor for an actuator. The cross slider form is applied at present. It succeeded in the miniaturization compared with the linear motor. In the VFP-type ventricular assist system, the blood contact parts are a central vibration tube with inflow and outflow chambers. We designed round diaphragms to prevent thrombus formation. In addition, we developed an energy transmission system for total implantation. The VFP creates a high frequency oscillated blood flow. It has a unique flow pattern. Brain blood flow increased although the total flow of the circulation did not change in the frequency of 25 to 30 Hz. The quantitative evaluation of the autonomic nerve function during the left heart assistance with an oscillated blood flow was carried out by spectral analysis. Some influences on an autonomic nerve were observed by the VFP left heart assistance. We will continue development research with the aim of clinical application.

Development of an implantable artificial anal sphincter by the use of the shape memory alloy

In this study, we developed and assessed an artificial anal sphincter driven by an shape memory alloy actuator (AS-SMA). The performance characteristics of the device were analyzed with a measurement system. Assessment showed that the AS-SMA could generate a pressure of 55 mm Hg at an atmospheric temperature of 36 degrees C, and displacement of the SMA actuator was 7.5 mm when the temperature of the SMA plate was 55 degrees C. To evaluate opening and closing, we studied a piglet colostomy model, in which the AS-SMA was implanted around the colostomy in the extraperitoneal space. Flow control tests using living porcine intestine revealed that the AS-SMA could maintain fecal continence against an intestinal pressure of 75 mm Hg. The high pressure zone corresponding to the location of the device was demonstrated in a manometric examination. For 6 days after surgery, we activated the AS-SMA twice a day and observed the bowel movements. The animal experiment indicated that the AS-SMA is able to control the bowel movements of patients with fecal incontinence if several problems, such as burning of tissue around the device and compression injury of the intestine, are resolved.

Automatic detection and classification of abnormalities for artificial hearts using a hierarchical self-organizing map

A hierarchical self-organizing map (SOM) has been developed for automatic detection and classification of abnormalities for artificial hearts. The hierarchical SOM has been applied to the monitoring and analysis of an aortic pressure (AoP) signal measured from an adult goat equipped with a total artificial heart. The architecture of the network actually consists of 2 different SOMs. The first SOM clusters the AoP beat patterns in an unsupervised way. Afterward, the outputs of the first SOM combined with the original time-domain features of beat-to-beat data are fed to the second SOM for final classification. Each input vector of the second SOM is associated with a class vector. This class vector is assigned to every node in the second map as an output weight and learned according to Kohonen's learning rule. Some experimental results revealed that a certain abnormality caused by breakage of sensors could be identified and detected correctly and that the change in the state of the circulatory system could be recognized and predicted to some extent.

Totally implantable ventricular assist system that can increase brain blood flow

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.

[Type A behaviour pattern and hypercholesterolemia in elder patients]

To examine the relationship between type A behavior pattern and hypercholesterolemia, we recruited 109 primary hypercholesterolemic patients without treatment for hyperlipidemia (30 males and 79 females) and then classified them according to Maeda's questionnaire into two groups; type A group (16 males and 35 females, aged 73.1 +/- 8.7) and type B group (14 males and 44 females, aged 71.3 +/- 8.7). We studied serum total cholesterol, serum triglyceride and BMI. Serum total cholesterol was shown significantly higher in type A group than that in type B (233.0 +/- 22.8 vs 223.9 +/- 14.2 p < 0.01) and BMI lower (24.0 +/- 3.9 vs 25.4 +/- 3.9 p < 0.05), however, there was no significant difference in serum triglyceride between two groups (148.96 +/- 8.2 vs 134.0 +/- 48.8). Although there was no significant difference in BMI, serum total cholesterol was significantly higher in the women's group and in the 60s. This study suggests that type A behavior pattern is related to lipid metabolism, however we should take gender and age into consideration to study the relationship between type A behavior pattern and lipid metabolism.

Evaluation of the inner-surface morphology of an artificial heart by acoustic microscopy

The total artificial heart (TAH) is being developed for permanent replacement of the natural heart instead of heart transplantation. The need for detecting the material fatigue in the TAH is increasing in order to guarantee long-term use. In this study, the inner surface morphology of the TAH was evaluated by a specially developed scanning acoustic microscope (SAM) system operating in the frequency range of 100-200 MHz. The inner sac of our TAH consisted of polyvinylchloride coated with polyurethane, and the SAM investigations were performed before and after the implantations in goats. The amplitude images of the SAM demonstrated protein adhesion on the inner surface of the TAH after the animal experiment, and the phase images showed distortion of the wall with spatial resolution of 0.2 microm. These results suggest the feasibility of a high-frequency ultrasound for evaluating the material fatigue of TAH.

Total vascular resistance and blood flow frequency during left ventricular assistance using a vibrating flow pump

A vibrating flow pump (VFP) can generate high frequency oscillated blood flow within 10-30 Hz by the oscillation of its central tube. A totally implantable artificial heart using a VFP is being developed as a unique type of blood pump. In this study, left ventricular (LV) assist circulation was performed using a VFP. The total vascular resistance and driving frequency of the VFP were estimated from their relationship. The effect of oscillation on the vascular system was studied by the frequency analysis method and vascular impedance. Adult goats were anesthetized by halothane using an inhaler and a left fourth thoracotomy was performed. The inflow cannula was inserted into the left ventricle, and the outflow cannula was sutured to the descending aorta. The VFP and a centrifugal pump were set in parallel for alternation and comparison. The driving frequency of the VFP was changed and included 15, 20, 25, and 30 Hz. The hemodynamic parameters were continuously recorded during experiments by a digital audio tape (DAT) data recorder. The internal pressure of the left ventricular cavity and aortic pressure were monitored by the pressure manometers continuously. One hundred percent LV assistance was judged by the separation of LV and aortic pressure. The total vascular resistance was decreased by the start of operation of each pump. The decrease during flow using the VFP was not as large as that using a centrifugal pump (CP). The arterial input impedance during oscillated blood flow by the VFP showed a slow curve appearance. It was similar to the frequency characteristics curve of natural heart beats within the lower frequencies. The study of arterial impedance may be important for the estimation of the reflection of the pulsatile wave from the arterial branch, among other things.

Detection of the cardiac function by fractal dimension analysis

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.