In this study, a bearing and motor system of the right heart pump was designed for a continuous flow total artificial heart. We evaluated the performance of the motor in the winch examination. Also, we examined the influence of the gap between the stator and the rotor under the constant drive voltage condition. The gap was changed from 1.0 mm to 2.5 mm. The motor with larger gap has higher rotational speed coefficient, and lower torque coefficient. On the other hand, the motor with smaller gap has lower rotational speed coefficient and higher torque coefficient. In shaft output, we could not find significant difference with the operational range. The motor with larger gap has lower efficiency when the torque is larger than 5.0 mNm. The motor with larger gap has higher efficiency when the torque is smaller than 5.0 mNm.

We have developed a new ultra-miniature axial flow blood pump to realize the Valvo pump that is implanted at the aortic valve position. The new ultra-miniature axial flow blood pump has a diameter of 24.5 mm and a length of 24.5mm, and the volume of the blood pump is 11.5 ml. the axial flow blood pump uses passive magnetic bearing for levitating in an axial direction and hydrodynamic bearing for a radial direction. The axial flow blood pump employs a ceramics inner housing to restrict edge-current loss. The axial flow blood pump was evaluated in vitro using 33 % glycerin solution. The axial flow blood pump had a pump outflow of 2.5 l/min against differential pressure of 50 mmHg at a motor rotational speed of 19000 rpm with an input energy of 9.5 W. Further studies are required including improvement of efficiency and miniaturization of the pump.

Sensor less estimation of pressure and pump flow has been an important subject for developing artificial hearts. However, estimated values are often incorrect influenced by the change in blood viscosity that changes with various factors. Therefore, viscosity estimation is essential for accurate estimation of pressure and flow. In previous study, we proposed viscosity estimation with table estimation method and in vitro study was performed using helical flow pump. However, dispersion was found with nonlinear characteristic of motor. In this study, we tried to improve viscosity estimation with modification of motor having linear characteristics. As a result, standard deviations of estimated viscosity reduced from 0.51 to 0.20. Consequently, dispersion of estimated pressure and flow could be reduced.

We have studied about titanium(Ti) micro porous scaffold for applying inflow and outflow's necking parts of VAD. To promote early new ingrowth of vascular intima, we developed an additional surface modification process for making the hydrophilic treatment.

Bulk Ti specimens were incubated into hydrogen peroxide solution for 48h in adequate temperature. After soaking the collagen solution on specimens' surface, top surface were fixed by the isocyanate-benzene solution.

Specimens were studied for the hydrophilic evaluation by measuring the contact angle, the quantification of collagen matrix, and the cell adhesion studies. Specimens showed fine hydrophilic properties, much fixation of collagen compared to the bulk control, and positive cell adhesion level than the control group. These results indicated the possibility of this treatment for the blood contacting devices as the promotive scaffold.

In a therapeutic situation with thin catheter using ultrasound, the inducing method with the catheter, which comes from inside to outside of human body, is essentially necessary. In the experiment, we formed two foci with opposite phase with 6 mm distance in 60 mm from the 2D array transducer (with 256 elements, frequency 1 MHz, and 120 mm curvature radius). According to the linear displacement of the foci in the azimuth direction, a catheter (diameter 0.2 mm) set between the two foci was bent with the maximum displacement of 0.19 mm as the cantilever law. From the result, we have confirmed the possibility to manipulate a thin catheter in the perpendicular position from ultrasound elements.

We have been developing a computer-controlled infusion system of cardiovascular drugs (vasodilator, inotropes, diuretics, volume-expander) to automatically optimize arterial pressure (AP), cardiac output (CO), and pulmonary wedge pressure (PCWP) in heart failure (HF). In our previous developments, CO and PCWP were measured through thoracotomy, which was impractical in clinical settings. Inotropes were inevitably infused, which was not in line with HF guidelines. We made the system less invasive and clinically feasible. Methods: CO and PCWP were estimated and monitored less-invasively utilizing transthoracic-echocardiography. Control algorithm was revised in accordance with the guidelines. We applied the system to 9 HF dogs. Results: Once activated, our system immediately started infusions of vasodilator/diuretics in all animals. Inotropes was not used in 3, and used at minimal doses in 6 animals that were intolerant of vasodilators. Hemodynamic variables were controlled to their targets accurately. Conclusion: Advanced system may be useful in managing patients with HF.

Background: Rho-kinase mediated vasoconstriction plays a key role in pulmonary hypertension (PH). We evaluated the acute effect of Rho-kinase inhibiter, Fasudil, on pulmonary artery input impedance (Z) in Sugen/Hypoxia rats. Method: We measured pulmonary artery pressure (PAP) and flow under irregular pacing and estimated Z in 3 weeks PH rats (n=6). Result: Fasudil significantly decreased PAP (50.5±6.4 vs 38.2±3.2 mmHg, p<0.01) and resistance (56.5±7.0 vs 39.9±5.2 mmHg/ml/sec, p<0.01), whereas increased compliance (1.82±0.4 vs 2.5±0.8 10^-3×ml/mmHg, p<0.05). Conclusion: Rho-kinase inhibitor equally lowers the gain of Z regardless of frequency examined.

There are no publications on CANS activity in different types of exercise by means of non-invasive CANS measurement like Heart rate variability. The purpose of this study is to examine cardiac autonomic nervous system (CANS) activity during two different types of exercise. Young male volunteers were participated in this experiment which was approved by Osaka Electro-Communication University Ethical Comittee.5 minute resting heart rate monitoring trials were performed before and after the exercise trials. An exercise trial gradually adds and then reduces physiological load between 60W and 200W. Another exercise trial made the subjects provided with constant physiological load at about 125W. Our results show that alterations of CANS activity between the trials are definitely different. Especially, it should be appriciated that, from our results, heart rate modulation with not only CANS activity but also catecholamine may be measured with non-invasive method.

Spiral reentry is thought that the abnormal excitation propagation during Ventricular tachycardia (VT) and fibrillation (VF). It was reported that intracellular calcium (Cai) rise just before VT develop VF which phanomenon is called "Cai burst". However interaction between Cai burst and VF initiation were still unclear. In this study, analyze between spatial heterogeneous Action Potential Duration (APD) and Cai amplitude during VT. Simultaneous optical mapping Vm/Cai was performed with Langendorff-perfused rabbit hearts during pacing and VF induced cross-field stimulation protocol. APD and Cai amplitude maps were constructed during pacing and VT both. APD and Cai amplitude altered spatially which magnitude increase each beat in VT. Cai amplitude alternans were larger than APD alternans. This results spatially discordant APD alternans and reentry generation. This results suggested that functional block line emerged alternans in VT is mechanisms of reentry generation.

Previous computer simulation research suggested "Phase shift" that the position of spiral reentry could be changed by low energy electrical point stimulus at the spiral reentry center. But the mechanisms of phase shift was still unclear. The objectives of this research was optical mapping image analysis of phase shift phenomenon using "phase variance" method. The optical mapping system was constructed by high-speed video camera, fluorescent dye (main wavelength=520 [nm]), micro-electrodes, Langendorff-perfused rabbit heart specimen and optically recorded (1000 [fps], 512x512 [pixels]).Image data was image processed to phase variance map, and analyzed with distance and interval map. Previous mechanisms of phase shift was explained that pair annihilation of two phase singularity and switched to another one. But our research found the new phase shift mechanisms that was the same rotational direction phase singularity were fused together.

The left ventricle (LV) plays an important role in pumping blood throughout the body. The LV motion is attributed to an electrophysiological mechanism, i.e. cardiac conduction system and excitation propagation, and mechanical mechanisms, i.e. contraction of the cardiac muscle fibers. In a sinus rhythm, the excitation propagates through the LV due to the electrophysiological stimulus of the heart muscle cells with a constant rhythm. However, in an arrhythmia, the stimulus rhythm becomes inconstant, and some arrhythmia with a severe abnormality results in a reduction of cardiac function. So far, although some computational studies considering the electrophysiological change during arrhythmia have been done, little is known about the effect of coupling mechanism between electrophysiological dynamics and the entire LV kinematic behavior. In this study, an electrophysiological-mechanical integrated LV model is developed, and the effects of the excitation propagations in both the normal and arrhythmia conditions on the LV kinematics are investigated.

Heart rate variabilities have been utilized as means to assess the autonomic activity. However, large individual variations prevent from consistent quantitative interpretation. This paper introduces personalized indices to concur the difficulty. Drug induced (Atropine and Propranolol) distinct physiologic states have been made and ECG data were obtained from 14 normal subjects. Personalized relative indices rLF, rHF, rLF/rHF, rMF and average/variance of HR have been utilized for the classification. An improved dichotomous classification scheme achieved average classification sensitivity of 0.91 and specificity 0.97 showing the effectiveness of proposed personalized indices.

Electrical excitation in the heart is initiate from a sinoatrial node located in the right atrium. The sinoatrial node is physiological pacemaker in normal heart. One of the mechanisms of supraventricular arrhythmia such as atrial fibrillation is a premature excitation conduction initiated from a pulmonary vein. To establish a method to determine the location of the premature excitation is required for ablation therapy in clinically. The purpose of this study is to develop the method to find the location of the premature excitation in the atria. Our developed system is able to convert 12-lead electrocardiogram to vectorcardiogram and analyze vector loops corresponding to excitation propagation in the heart. Using developed system, we analyzed electrocardiograms recorded from healthy persons and patients with implantable pacemaker. As a result, two groups were classified according to magnitude and direction of maximum P loop.