Kazuhiko Atsumi

Chitin is an effective material for sutures.

Chitin is an absorbable suture material with suitable mechanical properties. Tissue reaction is not specific and the good healing which ensued provided evidence for a satisfactory biocompatibility. Toxicity tests, including acute toxicity, pyrogenicity, mutagenicity were negative in all respects. The chitin suture was absorbed in about four months in rat muscles. The persistence of the tensile strength of the chitin was better than Dexon (TM) or catgut in bile, urine and pancreatic juice but weakening occurred early in the presence of gastric juice. Application in 132 patients proved satisfactory. Adverse effects were nil.

Can total artificial heart animals control their TAH by themselves? One year survival of a TAH goat using a new automatic control method (1/R control).

A total artificial heart (TAH) goat survived for 360 days on the new automatic control method (1/R control), in which the cardiac output of the TAH can be controlled through the cardiovascular center by making it function by reflecting the beta-adrenergic reaction in peripheral vascular resistance. This is thought to be the only long-term, real-time, measurable parameter by which information on the activity of the cardiovascular center can be received directly by the TAH system. In this goat, the hemodynamic parameters (RAP, AoP, and so forth) were kept within physiologic limits when control was stable, and the cardiac output was automatically increased in response to exercise, not unlike that in the natural heart. There were no abnormal blood chemical or hormone data except at end stage. Based on these results 1/R can be considered a physiologic control method for a TAH.

Development of transcutaneous energy transmission system for totally implantable artificial heart

A transcutaneous energy transmission system (TETS) was composed of a couple of coils, which formed a transformer across the skin, a driving circuit, and a rectifying circuit. By using coreless coils and a high driving frequency (100–160 kHz), more than 25 W of electric power could be transmitted with 78.5% of maximum efficiency (dc to dc). In animal experiments, the primary coil temperature during operation was under 39°C on thermograms. After 10 months of implantation of a secondary coil coated with epoxy resin, it was wrapped by a thin capsule of connecting tissue. No obvious tissue reaction was recognized.

Cytogenetic effects of argon laser irradiation on Chinese hamster cells.

The cytogenetic effects of argon laser light on V79 Chinese hamster cells were studied. Irradiation with a defocused continuous beam from an argon laser at doses of 100 to 400 J/cm2 had dose-related cytostatic and cytocidal effects. Cell cycle analysis by flow cytofluorometric measurement indicated that argon laser irradiation induced a temporary block at the G2 + M phase. The survival curve after laser irradiation was exponential without an initial shoulder and the D0 value (34% lethal dose) was calculated as 170 J/cm2. A significant increase in sister chromatid exchange was observed after laser irradiation. Laser irradiation also induced chromatid and chromosome aberrations, most of which were breaks and gaps. These chromosomal changes are probably not an artifact of the experimental procedures such as the use of phenol red and antibiotics or spontaneously emitted uv light. No mutation at the Na+/K+-dependent ATPase locus was induced by argon laser irradiation. Although the mechanism by which an argon laser beam induces cytogenetic damage remains to be investigated, the possible involvement of hyperthermia seemed to be excluded.

Over 500 Days’ Survival of a Goat with a Total Artificial Heart with 1/R Control

The 1/R control was developed to provide control over the output of a total artificial heart (TAH) by the central nervous system by using the peripheral vascular conductance (1/R) the vasodilatation in for the control signal. The physiologic stability of the 1/R control algorithm was tested by using goats with TAH. To apply the 1/R control equation to TAH in goats, real-time and continuous measurements of cardiac output, aortic pressure, and right atrial pressure were performed throughout the survival period. Left atrial pressure was also measured, to prevent lung edema. Under the 1/R control, 532 days’ survival was obtained in a goat with a TAH. Findings over the course of the experiment showed no hemodynamic or metabolic abnormality. Autopsy findings showed macroscopically no congestion in the liver. The experiment demonstrated the physiologic stability of the 1/R control algorithm for an extended period. Improvement of methods for measurement, such as the development of feasible techniques for the noninvasive measurement of the required hemodynamic parameters, will make it possible to use 1/R control in practice, especially for a totally implantable TAH system.

Fabrication of a jellyfish valve for use in an artificial heart

For a valve to be fabricated seamlessly into an artificial heart (AH) blood pump, a jellyfish valve has been developed, in which a thin membrane is fixed at the center of a valve seat having several spokes to protect against prolapse of the membrane. The valve is superior in performances to a Björk-Shiley valve, and reveals good blood compatibility. The valve would be very useful not only for AH animal study, but for future clinical use in infants to adults. Several institutions are already trying the valve. In this paper, the fabrication of the jellyfish valve is introduced, and in vitro and in vivo results summarized. A computer aided design (CAD) system was developed to cut a male wax mold of the valve seat. The input parameters to the CAD are diameter, height, thickness of rim, number of spokes, width and thickness of spokes, etc. Jellyfish valves with diameters of 4 to 27 mm have already been fabricated for many types of AHs and assist pumps.

The second and third model of the flow transformed pulsatile total artificial heart.

For the purpose of future total implantation, a new pulsatile total artificial heart, a flow transformed pulsatile total artificial heart (FTPTAH), in which the continuous flow from a single centrifugal pump (CFP) was converted to pulsatile flow by switching two three-way valves that could alternately perfuse the systemic and pulmonary circulation, was proposed, and the data from the prototype model were reported. As the next step, the second model, in which a CFP and a spool valve (SV) driven with a solenoid were fabricated in one piece, was made and tested in a mock circulatory system. The system could send 4.7 L/min of pulsatile output alternately to the pulmonary artery and aorta, with 30 and 100 mmHg afterload, respectively, at 3000 rpm CFP. However, three problems were encountered: the output was not enough, mixture or inversion of venous and arterial blood in the CFP would occur, and heat generation at the solenoid was very severe. To solve these problems, a third model was designed in the current study. To increase pump output, hydrodynamic analysis was performed. The SV was divided into inlet and outlet to control the blood mixture or inversion. To suppress heat generation, each SV was driven back and forth by two solenoids, one on each side of the SV. The model revealed satisfactory results in a mock circulatory system.

The Jellyfish Valve: A Polymer Membrane Valve for the Artificial Heart

The development of a polymer membrane valve for artificial heart blood pumps is very much required, since the mechanical valves, such as the Bjork-Shiley (BS) and Hall valves, used in the present artificial heart (AH) blood pumps have the following problems: 1. A ring thrombus is often formed at the interface between the valve ring and pump housing, because these cannot be fixed seamlessly. 2. Valve failure sometimes occurs at the disc and stent due to a water-hammer effect. 3. Regurgitant and leakage flow generated in the mechanical valve induces hemolysis and the AH patient becomes mildly anemic. 4. The valves are too expensive to popularize the AH as a therapeutic method.

Percutaneous Intradiscal Laser Discectomy

Recently percutaneous discectomy, such as chemonucleolysis with chymopapain [1] and percutaneous nucleotomy with punch [2] or nucleotome, has been developed extensively in Europe and America to provide an alternative to surgery in the treatment of lumbar disc herniation. But percutaneous nucleotomy, as mentioned above, has not been used in our daily therapy because of the limitation of indication, complications and technical problems. The experimental study of percutaneous intradiscal laser discectomy (PILD) has been tried to provide an alternative to percutaneous discectomies which are currently applied. The protocol of our study was composed of five parts. The five parts were as follows: 1) The optimum condition was obtained to vaporizes nucleus pulposus with Nd: YAG laser using sacrificed rabbit and goat lumbar discs. 2) The intradiscal changes in the time course were observed by microscopic evaluation using rabbit lumbar discs. 3) The relationship between intradiscal pressure (IDP) and vertical load in the time course were compared between irradiated discs, normal discs and control discs which were operated by curette. 4) Fibers and needles were developed to diminish heat damage. 5) Preliminary in vivo trial of PILD was performed in anesthetized young goats under X-ray guidance prior to the application for human cases.

Development of a New Circulatory Assist Method with the Combined Effects of Intra-Aortic Balloon Pumping and Counter Pulsation-First Report

Current circulatory assist methods, such as intra-aortic balloon pumping (IABP), are not always adequate to save acute circulatory failure patients. Therefore, a stronger, percutaneously accessible method is required. We found that the combination of IABP and CP generated a profound circulatory assist effect, and we have consequently developed a new assist system in this study. A sac type blood pump with a volume of 20 ml and a single port without a valve, was developed for CP. In the mock circulatory test, a 20 ml stroke volume was obtained using a cannula with a 5 mm diameter under the following driving conditions: air pressure = 200/-100 mmHg; S/D = 50%; pulse rate = 100 bpm. In vivo experiments were performed using four mongrel dogs with body weights of 12-20 kg. A cannula for CP was inserted via the brachial artery or subclavian artery into the aortic root. The pump flow (PF), coronary artery flow (CF), renal arterial flow (RF), and aortic pressure (AP) were measured, and the combined effects of IABP and CP were compared with their individual effects. In the most effective case, a marked increase in diastolic AP (60%), cardiac output (40%), and CF (100%) was obtained by the combination of IABP and CP, which produced a remarkable effect compared with the single use of IABP and CP. There was no negative effect on RF by this assist method. As this new circulatory support system has many circulatory assist effects, and is percutaneously accessible, it will be available for clinical use.