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Development have been achieved of a new blood pump for next generation Percutaneous Cardio-Pulmonary Support (PCPS) system and a novel surface coating method for silicone membrane hollow fiber by physical adsorption using a copolymer composed of a 2-Methacryloyloxyethyl phosphorylcholine (MPC) unit and a hydrophobic unit. The new blood pump, named the Troidal Convolution Pump (TCP), is based on the principle of a cascade pump and perfused 5 L/min and 350 mmHg at 2450 rpm. The novel copolymer composed of 30% MPC unit and 3-(methacryloyloxy) propyltris (trimethylsiloxy) silane (MPTSSi) unit (PMMSi30) was the most suitable molecular design on a silicone surface. The PMMSi30 coated surface adsorbed 7.2 % as much protein a non-coated surface adsorbed.

The helical flow pump (HFP) is newly developed blood pomp for total artificial heart (TAH). HFP can work with lower rotational speed than axial and centrifugal blood pump. It can be seen reasonable feature to generate pulsatile flow because high response performance can be realized. In this article, pulsatility of HFP was evaluated using mock circulation loop. Pulsatile flow was generated by modulating the rotational speed in various amplitude and heart rate. In the experiment, relationship between Pump flow, pump head, rotational speed amplitude, heart rate and power consumption is evaluated. As the result, complete pulsatile flow with mean flow rate of 5 L/min and mean pressure head of 100 mmHg can be obtained at ± 500 rpm with mean rotational speed of 1378 to 1398 rpm in hart rate from 60 to 120. Flow profiles which are non-pulsatile, quasi-pulsatile or complete flow can be adjusted arbitrarily. Therefore, HFP has excellent pulsatility and control flexibility of flow profile.

To realize a total artificial heart (TAH) with high performance, high durability, good anatomical fitting, and good blood compatibility, the helical flow TAH (HFTAH) has been developed with two helical flow pumps having hydrodynamic levitation impeller. The HFTAH was implanted in goats to investigate its anatomical fitting, blood compatibility, mechanical stability, control stability, and so on. The size of the HFTAH was designed to be 80 mm in diameter and 84 mm wide. The maximum output was 19 L/min against 100 mmHg of pressure head. Eight adult female goats weighting from 45 to 56.3 kg (average 49.7 kg) were used. Under the extracorporeal circulation, natural heart was removed at the atrioventricular groove and the HFTAH was implanted. The HFTAH was driven with a pulsatile mode. The 1/R control was applied when the right atrial pressure recovered. The HFTAH could be implanted with good anatomical fitting in all goats. Two goats survived for more than a week. One goat is ongoing. Other goats did not survive for more than two days with various reasons. In the goats that survived for more than a week, the hydrodynamic bearing was worn and broken, which indicated that the bearing touched to the shaft. The cause was supposed to be the influence of the sucking effect. The potential of the HFTAH could be demonstrated with this study. The stability of the hydrodynamic bearing in a living body, especially the influence of the sucking effect, was considered to be very important and a further study should be necessary.

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.

The authors have been developing a mechano-electric artificial myocardial assist system (artificial myocardium) which is capable of supporting natural contractile functions from the outside of the ventricle without blood contacting surface. In this study, a nano-tech covalent type shape memory alloy fibre (Biometal, Toki Corp, Japan) was employed and the parallel-link structured myocardial assist device was developed. And basic characteristics of the system were examined in a mechanical circulatory system as well as in animal experiments using goats. The contractile functions were evaluated with the mock circulatory system that simulated systemic circulation with a silicone left ventricular model and an aortic afterload. Hemodynamic performance was also examined in goats. Prior to the measurement, the artificial myocardial assist device was installed into the goat's thoracic cavity and attached onto the ventricular wall. As a result, the system could be installed successfully without severe complications related to the heating, and the aortic flow rate was increased by 15% and the systolic left ventricular pressure was elevated by 7% under the cardiac output condition of 3L/min in a goat. And those values were elevated by the improvement of the design which was capable of the natural morphological myocardial tissue streamlines. Therefore it was indicated that the effective assistance might be achieved by the contraction by the newly-designed artificial myocardial assist system using Biometal. Moreover it was suggested that the assistance gain might be obtained by the optimised configuration design along with the natural anatomical myocardial stream line.