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We developed a small, lightweight, low-cost implantable ventricular assist device (VAD) for use in smaller Japanese subjects. The major advantage of this pump is the simplicity of its fabrication. Most parts of the pump were shaped from a transparent acrylic block by a turning process, and the diaphragm was made from a silicon sheet. Since this method of construction did not require any complex processes, we could manufacture many pumps of various shapes. We determined the most efficient shape for the Ebacor VAD using the flow visualization technique. The pump showed an output above 6 liters/min under a driving pressure of 300/-100 mmHg. The pump performance of current VADs is superior to that of the Ebacor VAD, because these pumps are larger. Since the Ebacor VAD is small in size, it can be driven by the driving system of a normal IABP control unit, which many hospitals already have in place. During a 30day continuous driving performance test of this pump, no problems like performance decrements or water and air leakage were observed.

We have produced an eccentric roller type total artificial heart (ERTAH). As the first step in the development of this ERTAH, we conducted simulations such as a numerical simulation, a mock test, and an acute animal experiment using DeBakey roller pumps to analyze the left-right balance during its operation. The next step was redesigning the blood chambers to improve energy efficiency and implanting the ERTAH with an interatrial shunt into an animal for evaluation of the in vivo performance of the device. In the simulations, shunt flow through the bronchial arteries was approximately 500-600mlJmin, and the interatrial resistance was varied from 2.9-7.7 mmHg・min/liter. Redesigning the blood chambers resulted in the mock test in a 20% increase in energy efficiency, about a two-fold increase in cardiac output and improved durability compared to the previous type in the mock test. In the animal experiment the ERTAH operated with a left flow rate of 6.0 liters/min and a right flow rate of 5.4 liters/min. The interatrial shunt flow rate was 250-400m1Jmin. Creating an interatrial shunt is a useful method for balancing the blood flow between the left and right heart of the ERTAH. A decrease in friction resistance and the prevention of backward flow resulted in an increase in energy efficiency, cardiac output, and improved durability, in spite of downsizing the blood chambers., This work was supported in part by a Research Grant for Cardiovascular Disease 10C-2 from the Ministry of Health and Welfare, Japan.

Prevention of cardiac and vascular dysfunction with pretreatment has been accepted as an important factor in heart transplantation. Ginsenosides (GS) have been reported to have some beneficial effects on the cardiac and vascular system. We hypothesized that pretreatment with GS would result in an improvement of functional recovery after a 12 hour (hr) rat heart preservation. A Langendorff apparatus was applied to estimate the cardiac and vascular function in an isolated rat heart preparation. The hearts were preserved in University of Wisconsin solution at 0°C for 12hr, after pretreatment with 0.9% sodium chloride or GS 100 mg/kg, respectively, in control (n = 9) and GS (n = 14) groups. After storage, the cardiac function, myocardial water content, and coronary vasodilatory response were evaluated. The GS group showed a significantly higher recovery percentage of cardiac function compared with the control group: aortic flow 81.4 ± 21.4% versus 57.2 ± 11.0% (p = 0.0052); coronary flow 81.4 ± 14.5% versus 57.2 ± 6.0% (p = 0.0001); ±dp/dt max 72.5 ± 16.1 % and 66.0 ± 16.1 % versus 53.7 ± 4.1 % and 51.4 ± 7.1 % (p = 0.0027 and p = 0.0189) respectively. The GS group showed a lower increase in myocardial water content. With Langendorff perfusion, the endothelial and vascular smooth-muscle cell function were evaluated by an increasing percentage of coronary flow in response to acetylcholine chloride (0.3 × 10-7 mol/liter) and nitroglycerin (0.5 × 10-5 mol/liter). It was significantly higher in the GS group than that in the control group (19.2 ± 8.8% and 28.0 ± 14.1% versus 9.9 ± 4.7% and 14.7 ± 8.1%, p = 0.008 and p = 0.0187, respectively) at the first minute. These results suggest a protective effect on ventricular and coronary vascular function in the rats pretreated with Ginsenosides, indicating potential benefits for long-term heart preservation.

We have developed a practical, low-cost ventricular assist device (VAD) comprising a newly designed blood chamber with a silicone lenticular sac and two silicone tri-leaflet valves (STV), made en bloc. This new VAD is seamless, can be made cost-effectively and assembled with the blood chamber and valve as one body. This novel design should reduce the incident of thrombus formation because of the absence of a junction at the connecting ring and because of the use of flexible silicone materials which have both antithrombogenecity and biocompatibility. In in vitro hemodynamics testing, a batch of 3 consecutively manufactured V ADs with STV s underwent hydrodynamic functional testing. These showed less regurgitation, a lower value of water hammer phenomenon, and a slightly greater pressure gradient across the valves than a mechanical valve (MV) [Björk-Shiley monostrut valve]. The flow and pulsatile efficiency were adequate and similar to that of a VAD with MVs. In in vitro durability and hemolysis tests, a V AD with STV functioned well for 54 days and showed similar hemolytic profiles to a V AD with MVs. In an in vivo acute experiment using an adult sheep, our device was promblem-free providing sufficient output as a left ventricular assist device (LVAD). Although it will be necessary to decrease the pressure gradient across this STV in the future, our device showed efficient performance as a practical and cost-effective V AD for short term use., This work was supported in part by the Tsuchiya Foundation and by a Research Grant for Cardiovascular Diseases (7A-1) from the Ministry of Health and Welfare, Japan

An assistance artificial heart was fabricated with blood compatible polyurethane having 3 different sizes and was evaluated by a series of preclinical experiment in calves. The following results were obtained. 1) The artificial heart was constructed in 3 sizes of 60, 80 and 100 cc in capacity and is activated by a pneumatic heart driver console. 2) The mock circulation revealed that this assistance heart has ejection fraction of 80-95%. 3) Safe use of assistance heart has been confirmed by implantation in 18 calves with intact or failured hearts over a period of 3 months. 4) Weaning could be performed in cases where myocardial necrosis of the left ventricle is induced less than 35% utilizing myocardial injection of 5N-NaOH. However pump dependency develops for a necrosis exceeding 35 %. 5) Thus we concluded that this system can be safely employed for a one month cardiac assistance clinically and at most for a 3 months support in pump dependent cases. 6) The technique was developed to make the instant shift possible within a few minutes from the conventional non-pulsatile bypass assistance to the assistance heart.

A new actuator using a cylindrical linear pulse motor for the artificial heart is proposed with descriptions of the principle of operation, theoretical expression of thrust, and experimental results. The actuator has a simple configuration and its size is much smaller than the ordinary external backup facility using a pneumatic power. The actuator consists chiefly of a linear pulse motor and two rooms of sacs for the right and left ventricles. Some problems have been found to be solved before the actuator can be applied to the actual artificial heart., Article, 信州大学工学部紀要 56: 59-72 (1984)