Biomedical subjects

Makoto Yoshizawa

Publications and source records attributed to Makoto Yoshizawa.

At least 19 recordsLinked to original sources

PubMed2006

Intravascular two-dimensional tissue strain imaging.

Our goal is to achieve the precise quantitative imaging of tissue elasticity in clinical settings. In the present study, we measured basic ultrasonic characteristics of atherosclerosis by two-dimensional (2D) intravascular tissue velocity imaging. Radio-frequency (RF) signal from a clinically used IVUS apparatus was digitized at 500 MSa/s and stored in a workstation. First, the correlation coefficient between two consecutive frames was calculated in the rotational direction and the rotational disuniformity was corrected to obtain the maximum correlation coefficient. Then, the polar coordinate images were converted into rectangular coordinate images and the images were divided into 64 by 64 square shaped regions of interest (ROIs). The correlation and displacement of the ROIs between the consecutive two frames were calculated by template matching method. Two-dimensional tissue velocity was defined as the vectors of displacement of ROI with 0.7 and more correlation. IVUS studies were performed in directional coronary atherectomy (DCA) procedures. The specimens excised by DCA were stained with Elastica-Masson's trichrome staining and CD68 immunochemical staining. Eleven cases (including two no re-flow cases and one perforation case) were intraoperatively observed by IVUS and the specimens obtained by DCA were observed by optical microscopy. The specimen from homogeneous 2D strain was collagen dominant fibrosis and the specimen from a lesion with complex vectors contained CD68 positive cells and degenerated collagen fibers, which indicated the plaque was vulnerable.

Algorithms↗

PubMed2006

Virtual reality pencil and paper tests for neglect: a protocol.

Hemispatial neglect is a common disorder that can occur after a lesion in the right hemisphere. Its main characterization is the difficulty in processing visual stimuli emanating from the space contralateral to the lesion. Pencil and paper tests (such as target cancellation, line bisection, or drawing copy) are used to diagnose neglect. We propose using virtual reality technology and haptic force feedback to enhance pencil and paper tests. Our system can track the patients' eye-gaze and their hand movements. Also, the efficiency of several techniques used to decrease the neglect in different sensory spaces are investigated.

Computer Simulation↗

PubMed2005

Automated drug delivery system to control systemic arterial pressure, cardiac output, and left heart filling pressure in acute decompensated heart failure.

Pharmacological support with inotropes and vasodilators to control decompensated hemodynamics requires strict monitoring of patient condition and frequent adjustments of drug infusion rates, which is difficult and time-consuming, especially in hemodynamically unstable patients. To overcome this difficulty, we have developed a novel automated drug delivery system for simultaneous control of systemic arterial pressure (AP), cardiac output (CO), and left atrial pressure (Pla). Previous systems attempted to directly control AP and CO by estimating their responses to drug infusions. This approach is inapplicable because of the difficulties to estimate simultaneous AP, CO, and Pla responses to the infusion of multiple drugs. The circulatory equilibrium framework developed previously (Uemura K, Sugimachi M, Kawada T, Kamiya A, Jin Y, Kashihara K, and Sunagawa K. Am J Physiol Heart Circ Physiol 286: H2376-H2385, 2004) indicates that AP, CO, and Pla are determined by an equilibrium of the pumping ability of the left heart (SL), stressed blood volume (V), and systemic arterial resistance (R). Our system directly controls SL with dobutamine, V with dextran/furosemide, and R with nitroprusside, thereby controlling the three variables. We evaluated the efficacy of our system in 12 anesthetized dogs with acute decompensated heart failure. Once activated, the system restored SL, V, and R within 30 min, resulting in the restoration of normal AP, CO, and Pla. Steady-state deviations from target values were small for AP [4.4 mmHg (SD 2.6)], CO [5.4 ml x min(-1) x kg(-1) (SD 2.4)] and Pla [0.8 mmHg (SD 0.6)]. In conclusion, by directly controlling the mechanical determinants of circulation, our system has enabled simultaneous control of AP, CO, and Pla with good accuracy and stability.

Animals↗

PubMed2005

Dysfunctional baroreflex regulation of sympathetic nerve activity in remitted patients with panic disorder. A new methodological approach.

BACKGROUND: Many researchers have studied the abnormalities of autonomic nervous system (ANS) such as decreased heart rate variability, which is a risk factor for sudden cardiac death, in patients with panic disorder (PD). However, no consistent abnormality has been uncovered to date. One of the reasons for this controversy may be due to the fact that most of these conventional studies have analyzed each physiological variable independent of other indices. We examined the ANS in PD patients using a new method which can more directly investigate the function of the baroreflex by examining the relation between the blood pressure (BP) and heart rate (HR). METHODS: During rest and audiovisual stimulation (AS) as mental stress such as being exposed to video imaginary of experiences such as driving motor vehicles, cardiovascular parameters, HR and BP were consecutively measured in 13 remitted PD patients and twenty aged and gender-matched normal controls (NC). In this study, to assess the cardiovascular ANS function (baroreflex) in PD we used the power spectrum analysis as usual and the mean of lag time (tau) between the Mayer wave components, which was closely related to sympathetic nerve activity of vasomotor, of HR and BP variability as a new trial. RESULTS: The PD patients and NC did not differ with regard to the power spectrum analysis of the heart rate. We found that tau in the PD group was significantly shorter than that in the NC both before and after AS, especially before. CONCLUSIONS: These findings suggest that remitted PD patients may have a dysfunctional baroreflex regulation of sympathetic nerve activity.

Acoustic Stimulation↗

PubMed2005

Development of the pulsation device for rotary blood pumps.

A rotary blood pump (RP) is desirable as a small ventricular assist device (VAD). However, an RP is nonpulsatile. We tried to develop a device that attaches a pulse to the RP. We also tried to develop a pulse-generating equipment that was not air-pressure driven. The ball screw motor was considered a candidate. The application of a small-sized shape memory alloy was also attempted. An electrohydraulic system was adopted, and actuator power was connected to the diaphragm. The diaphragm was placed on the outer side of the ventricle. Most RPs that have been developed all over the world drain blood from the ventricle. The wave of a pulse should be generated if a pulse is added by the drawn part. The output assistance from the outer side of the ventricle was attempted in animal experiments, and the device operated effectively. This device can be used during implantable operation of RP. This may serve as an effective device in patients experiencing problems in peripheral circulation and in the function of internal organs.

Animals↗

PubMed2005

Non-blood contacting electro-hydraulic artificial myocardium (EHAM) improves the myocardial tissue perfusion.

Artificial heart (AH) and ventricular assist devices (VAD) are widely used in the clinical setting to assist severe heart failure patients. The concept of direct cardiac compression (DCC) has been in use for several decades and has advantages over intravascular VAD. The process involves compressing the dysfunctional heart from its epicardial surface to avoid the thromboembolic events and decrease the complications and mortality. An Electro-hydraulic Artificial Myocardium (EHAM) system was designed and fabricated by Tohoku University. This system may assist cardiac contraction and create pulsatile blood flow. The aim of this study was to clearly define the hemodynamic efficiency of the EHAM system in myocardial tissue perfusion during its application in acute animal experiment. Eight healthy adult goats were used; left lateral thoracotomy was performed and the chest was opened by the resection of the 4th and 5th ribs. Hemodynamic parameters including ECG, blood pressure and cardiac output were continuously monitored. Myocardial tissue perfusion was measured by using Omega flow laser fiber attached to the surface of the heart. During the EHAM compression, and increase in blood pressure and myocardial tissue perfusion was observed in all animals when compared with pre-assisted mode. To conclude, EHAM effectively improves myocardial tissue perfusion and increases the pressure on the initiation of direct cardiac compression immediately. Thus it can be a potentially valuable adjunct in the management of severe heart failure.

Animals↗

PubMed2005

Diagnosis and rehabilitation of hemispatial neglect patients with virtual reality technology.

Victims of a stroke or an accident with damage on the parietal lobe can suffer from hemispatial neglect. This disorder is characterized by misperception of the space contralateral to the damaged area. Paper and pencil tests, such as line bisection tests, are used to diagnose hemispatial neglect. Unfortunately, they fail to quantify the degree of the neglect. Moreover, the neglect has different manifestations in each sensorial space and frame of references. In order to diagnose disorders of spatial recognition and analyze the neglected area in visual and somatic spaces, we developed a 3D-haptic virtual reality system coupled with an eye-tracking device. The haptic interface was used to interact with virtual objects. The virtual world can use the eye-gaze information to let patients overcome the neglect. We tested the system at a rehabilitation center and observed different approaches between normal subjects and hemiplegics patients. The first group was getting close to the target and then slowed down to grab it, whereas the later group proceeded by trial and error. The feature of trajectories of the hand in the 3D space could be used to determine the degree of the motion handicap. However, more specific virtual worlds are needed for efficiently extracting the feature of the patients.

Adult↗

PubMed2004

A Japanese-Russian collaborative study on aging and atherosclerosis.

In Russia, the average life span is decreasing. This phenomenon has not been previously observed in the western hemisphere during periods of relative peace. Although this trend can be attributed to various causes, the available statistics suggest that approximately 55% of the total mortality in Russia at the present time is due to cardiovascular events. Similarly, cardiovascular events are also increasing in Japan and are associated with changes in eating habits. A Japanese-Russian international collaborative study was therefore initiated to investigate this. Data on 102 normal Russian subjects were obtained from a total of 345 patients treated at the Smolensk State Medical Academy outpatients' clinic. The data on the Japanese patients were collected at Tohoku University, Tohoku Rosai Hospital, and Fukuda Denshi Company. Sixty-seven healthy male Japanese volunteers were compared with 44 healthy male Russian patients. In this study, Vasera VS1000 (Fukuda Denshi, Tokyo) was utilized to measure pulse wave velocity (PWV). Linear regression analysis was performed, and the results showed that brachial-ankle PWV (baPWV) was significantly higher in the Russian compared with the Japanese study group. With regard to aging, PWV was found to increase both in the Japanese and Russian subjects, with a significant increase in the latter group during their 40s compared with the Japanese, and with this tendency being carried forward into the 50s. This may be the principal cause for the higher incidence of cardiovascular events reported among Russians. Furthermore, when a straight line regression analysis was performed, the zero axis intercept in both cases showed almost the same value. These results indicated that the PWV may be almost the same in Japanese and Russian populations at the time of birth. In conclusion, at the time of birth, there is no difference in the atherosclerotic status of Japanese and Russian infants. However, over time atherosclerosis becomes more apparent and progresses significantly in the case of Russian subjects. This finding is observed through the analysis of PWV. The present authors intend to continue their study aimed at preventing the further development of atherosclerosis through medical intervention.

Aging↗

PubMed2004

Brachio-ankle pulse wave velocity and cardio-ankle vascular index (CAVI).

In order to diagnose arteriosclerosis in any part of the body, pulse wave velocity (PWV) measurement is a useful approach. However, it is considered that the technique of PWV measurement should be simplified. A new method for measuring PWV has therefore been proposed in Japan. The PWV of the brachial artery (ba) and the ankle was measured by applying air pressure with the aid of a volume plethysmograph. Comparisons between the baPWV measurement method and the conventional method are currently being performed. Since satisfactory results have been obtained to date, baPWV has gained popularity throughout Japan. Since this method measures PWV in the arm and foot, it may be said that aortic PWV is not reflected though a large amount of past PWV measurements. BaPWV is influenced by blood pressure. With the baPWV technique, blood pressure compensation is not carried out. Furthermore, the pulse pressure is measured by air pressure; therefore any stimulus that exerts pressure on an artery may influence these results. Due to these reasons, a cardie-ankle vascular index (CAVI) has been proposed in which the pressure wave form indicating the closing of the aortic valve appears in the form of an arterial pressure wave after a fixed delay time. This delay is the time difference between the actual closing of the aortic valve and the measuring point. Prior to the introduction of baPWV, PWV was measured in the carotid artery and foot. As in traditional PWV, baPWV uses the delay time, but between the brachial artery and the ankle artery. However, the carotid artery differs from the brachial artery, and the measured value differs depending on whether the arteriosclerosis is present in the carotid artery or the brachial artery. CAVI is calculated from the ECG, PCG, brachial artery waveform and ankle artery waveform using a special algorithm. This new method represents a breakthrough in the diagnosis of atherosclerosis.

Ankle↗

PubMed2004

Addition of rhythm to non-pulsatile circulation.

The development of a rotary blood pump (RP) is desirable as it can be used as a small ventricular assistance device (VAD). However, a RP does not generate any pulse. It may be physiologically better for the patient if the RP could generate a pulse. We have attempted to develop a device that produces a pulse in the RP. Intra-aortic balloon pumping (IABP) is effective in producing a pulse. However, the IABP cannot be implanted inside the body. Therefore, an attempt was made to develop pulse-generating equipment that was not driven by air pressure. The ball screw motor was considered as a possible candidate. In the future, we plan to apply small shape memory alloys. An electrohydraulic system was adopted, and actuator power output was connected to the diaphragm. The diaphragm was placed outside the ventricle. Most RPs developed throughout the world drain blood from the ventricle. The pulse wave should be generated if a pulse is added by the part from which blood is being drawn. In this study, animal experiments were conducted and the output assistance was tested from outside the ventricle. The device operated effectively in the animal experiment. The RP can easily be equipped with this device at the time of performing the implant operation. For a patient with problems of peripheral circulation and the internal organ function, it may prove to be an effective device.

Animal Experimentation↗

PubMed2004

Open-loop analysis of transfer characteristics from blood pressure to heart rate using an effectively total artificial heart.

It is desirable for the dynamic behavior of the drive rate of the artificial heart to be as similar as possible to that of the recipient's heart rate (HR) before implantation. This requires a model which can simulate the behavior of HR on the basis of only the information measured with the limited number of approvable implanted sensors. This article provides a linear time series model for explaining the behavior of HR only with aortic pressure and right atrial pressure. This could be obtained from open-loop analysis using a total artificial heart, which was introduced for measuring HR in vivo and for eliminating its effect on blood pressure. The model was identified in a goat equipped with a special biventricular assist device called the effectively total artificial heart (ETAH). The ETAH was introduced to make an open loop and awake situation in the animal with almost intact autonomic nerves, which could enhance the accuracy and reliability of the identification of the model. The adequacy of the proposed model was ascertained in several data sets measured in two goats, which were different from the data set used for identification. Most of the mean estimation errors were less than 3 beats/min and auto-correlation analysis showed approvable statistical appropriateness. However, it was clarified through comparison with the 1/R control method that the proposed model has a few problems still to be solved before its future implementation as an automatic controller of the TAH.

Animals↗

PubMed2004

Development of an implantable undulation type ventricular assist device for control of organ circulation.

It is well known that a rotary blood pump (RP) is effective as a small ventricular assist device (VAD). It might be still more effective if pulsation was available. The undulation pump (UP), which is a type of small RP, can also produce pulsation. In Japan, a development project for an implantable type UP ventricular assist device (UPVAD) is now advanced. Six universities and some companies together have been in charge of the development project for 5 years. In this study, the influence which the UP under development has on circulation in internal organs was investigated. Goats with the same weight as an average Asian person were used for the experiment. The left chest cavity was opened after resection of the fourth rib and the heart was approached. A cannula was inserted in the left ventricle from the apex. An outflow cannula was inserted into the left descending aorta. Heart muscle was excised using a newly developed puncher. The UPVAD was implanted using a left-heart bypass system. The myocardial blood flow, carotid arterial blood flow, and the kidney blood flow were recorded together with an electrocardiogram, blood pressure, and the flow rate. In these animal experiments, the blood circulation dynamic state was stabilized and sufficient support of the left heart was observed. Myocardial blood flow, carotid arterial flow, and a kidney blood flow increase resulting from UPVAD support was observed. Often the problem of multiple organ failure is important at the time of clinical application of a ventricular assist device. Assisting circulation to internal organs is important for prevention of multiple organ failure. It was concluded that the UPVAD might be useful for prevention of multiple organ failure.

Animals↗

PubMed2004

Component engineering for an implantable system.

Component engineering is important for the development of implantable-type rotary blood pumps (RP). The authors are conducting elementary development of an implantable artificial heart. A sensor system detects information in the living body. An automatic control system performs the drive control. Energy is provided by a transcutaneous energy transmission system (TETS). Various artificial hearts are being created. Miniaturization resulting from an increase in operating frequency is planned. A vibrating flow pump (VFP) has a reduced size of pumping chamber because of the high-speed reciprocating movement. Undulation pump ventricular assist devices (UPVAD) are small, lightweight rotary pumps. VFPs are useful in the medical treatment of multiple organ failure (MOF). UPVADs are planned to be permanent-use RPs. The purposes of these two artificial hearts differ, although they have a common component. The authors are developing TETS by using amorphous fibers, making efficient power transmission possible. Control information input from a micro or nano sensor is realized. A control algorithm has been developed and baroreflex control has been successful. Artificial heart development, fully exploiting component engineering, continues.

Animals↗

PubMed2004

Validity of the adaptive filter for accurate measurement of cardiac output in impedance cardiography.

The purpose of this study was to assess the validity of an adaptive filter, the scaled Fourier linear combiner (SFLC), in the impedance cardiography (ICG). Eight healthy males underwent constant-load bicycle exercise at different intensities from unloaded to near maximal intensity. The stroke volume (SV) and cardiac output (Q) measured by ICG at each condition were compared with those by the CO2 rebreathing method. We found that the noises were greatly reduced in the impedance waveform and that the inflection points, so-called the B- and X-points, were clearly detected even during strenuous exercise using the SFLC. Although a high correlation was observed between Qs measured by the two methods, the mean values of Qs in each method differed significantly and the regression line also differed significantly from the identity line. Likewise, a significant correlation was observed between SVs obtained by the two methods, but a significant difference in the group mean values and a trend of the regression line were observed. These findings suggest that the use of SFLC in ICG improves the performance in eliminating the noises and in detecting the inflection points in the waveform, thereby contributing to the accurate and beat-to-beat measurements of SV and Q especially during exercise.

Adult↗

PubMed2004

Beat-to-beat evaluation of systolic time intervals during bicycle exercise using impedance cardiography.

In order to elucidate the beat-to-beat changes of the systolic time intervals (STI) during exercise, we proposed new techniques relating to an adaptive filter and detection algorithms for B- and X-points in the impedance cardiograph (ICG). Six male subjects underwent a ramp bicycle exercise up to maximum intensity during which an ECG, ICG and phonocardiogram (PCG) were continuously measured. Following the application of an adaptive filter, the scaled Fourier linear combiner (SFLC), to the first derivative (dZ/dt) of the base impedance (deltaZ) and PCG waveforms, the B- and X-points were automatically determined. For the B-point detection we used three criteria: the zero-crossing point (B(zero)), the 15% response point (B15%) of the negative peak of the dZ/dt (dZ/dt(min)) and a new algorithm (B(new)). The X-point was separately determined by using the ICG and PCG waveforms. It was found that the shape of the dZ/dt waveform directly affected the determination of the B- and X-points. The B-points determined using B(zero) and B15%, criteria were sometimes unstable caused by the location of a notch preceding the dZ/dt(min) compared to the B(new). The time difference between the X-points measured by the ICG and PCG was mostly within +/- 20 milliseconds but statistically significant. Although a wide variation was seen in R-R intervals, the STI were more stable. The relationships between HR and STI from rest to maximal exercise showed a gentle curvilinear relationship. It is suggested that the STI can be obtained precisely on a beat-to-beat basis by using the adaptive filter and detection algorithms for the inflection points of the ICG even during maximum exercise.

Adult↗

PubMed2003

Can personality traits predict pathological responses to audiovisual stimulation?

The "Pockemon shock" is the most famous accident in the history of the broadcasting industry in Japan. Based on the experiences of this unfortunate accident from famous animation program "Pocket Monster", this study focused on the psychology and psychosomatics of the patients. A head-mounted display was used as the three-dimensional image presentation device and "Descent", a free software shooting game, was used as the software. Ten healthy adult male volunteers were used in this experiment after obtaining their informed consent. The oxygen metabolic change in the anterior lobe of the brain was measured by near infrared spectroscopy and recorded on an electrocardiogram. The mental scaling tendency of the object was analyzed using the type A behavior pattern and the hostility scaling. The Cook and Medley hostility (HO) scale from the Minnesota multiphasic personality inventory (MMPI) was also used in this experiment. From this scaling methodology, the paranoid scale, cynicism scale, lie scale, social support quality and social support quantity were calculated. All measured time series data were kept in the normal range, and no fatal arrhythmia or epilepsy were observed during experiments. In some cases, the brain oxygen metabolism may completely differ for the objects of Type A and Type B behavior patterns. On the whole, correlation did not become significant in type A scaling and hostility scaling. In a comparison of the percent changes of the HF in HRV with lie scaling, significant negative correlation was observed. The social support quantity was calculated from Cook and Medley, and significant negative correlations were observed with percent changes of LF/HF in HRV. The lie scale and social support quantity are opposite scaling. The sympathetic nervous system and parasympathetic nervous system have an opposite function also. Therefore, our results showed an interesting phenomenon, when considering the relationship between the autonomic function and the pathophysiological reaction to the audiovisual stimulations. As for the photo sensitive epilepsy, it was reported to be only 5-10% for all patients. Therefore, 90% or more of the cause could not be determined in patients who started a morbid response. The results in this study suggest that the autonomic function was connected to the mental tendency of the objects. By examining such directivity, it is expected that subjects, which show morbid reaction to an audiovisual stimulation, can be screened beforehand.

Acoustic Stimulation↗

PubMed2003

Artificial myocardium with an artificial baroreflex system using nano technology.

Where is the place which should be helped in a patient with congestive heart failure? The answer may be contraction of the heart. At Tohoku University, development research of "the artificial myocardium" has been conducted, using a ball screw type electromagnetic motor. Furthermore, super-miniaturization is being attempted at present. Thus, a system with shape memory alloy is being developed. The cooling speed problem was solved by the application of the Peltier element. A drive at a speed equal to that of a heartbeat was realized by the application of this system. At present, a ventricular assist device is used for patients waiting for a heart transplant in Japan. An air driven type system disturbs a patient's QOL remarkably because it is connected to the drive device. With our concept, energy is provided by using the electromagnetic force from outside of the body by the use of transcutaneous energy transmission system. Magnetic shielding by amorphous fibers was used at Tohoku University to improve the total efficiency. A natural heart can alter the cardiac output corresponding to the demand. Artificial internal organs must participate in the system of the living body, too. Tohoku University has developed a resistance based artificial heart control algorithm, which simulated a baroreflex system to cope with every demand. Nano level sensing equipment is now under development at Tohoku University. At present, development is being conducted aiming at an "intelligent artificial myocardium".

Baroreflex↗

PubMed2003

In vivo test of pressure head and flow rate estimation in a continuous-flow artificial heart.

To avoid using sensors with low biocompatibility and low durability in implantable total artificial heart (TAH) systems, the authors previously proposed a new method for estimating instantaneous values of flow rate and pressure head on the basis of voltage, current, and rotational speed in a motor driven centrifugal pump. The previous in vitro experiments showed that the proposed estimator could automatically compensate for the effect of the change in blood viscosity on the estimation accuracy by employing two kinds of autoregressive exogenous models. In this study, validity and reliability of this estimation method were ascertained in an acute animal experiment. In the experiment, two centrifugal blood pumps were implanted into an adult goat as a total artificial heart. Results of estimation were compared with true values when blood viscosity was changed by injecting physiological saline. The results indicated that the system could successfully estimate pressure head by compensating the change of viscosity, although the estimation accuracy of the in vivo estimation was not so high as that of the previous in vitro tests.

Animals↗