a hepatic support apparatus using isolated liver cells suspensions was tested in dogs with surgically induced acute hepatic insufficiency.
Experimental acute hepatic failure was produced in 15 dogs by a two-stage procedure consisting of a portal vein-inferior vena cava (end-to side) anastomosis followed in 3 to 4 weeks by ligation of the proper hepatic artery.
Seven animals received infusions of parenteral fluid alone to serve as controls, from which serial blood samples were collected during the observation period. The remaining 8 animals were subjected to a 3-hours liver support treatment with isolated rabbit liver cells, beginning 9 hours after the operation.
Liver support apparatus:
1)Plate type, with NUCLEOPORE membrane filter (NMF): The cell suspension enclosed with NMF (pore size: 0.6um) was constantly agitated by means of pulsation flow pump. (NMF allows plasma to pass through freely and, therefore, is used for plasmapheresis as well.)
2) Hollow fiver type, with polyvinyl alcohol membrane (PVA):
Volume of cell suspension, 40ml.
Controls showed an average survival time of 18 hours whereas all animals with perfusion with liver support showed prolongation of survival, with suppression of ammonia elevation in those surviving for more than 24 hours.
The longest survival achieved in the treated group was 26 hours. The data indicate that the provides some clinical benefit in the management of hepatic insufficiency.

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The present experiment was disigned to evaluate metabolic abilities of a prototype for a hybrid artificial liver. The module utilizing polyacrylonitrile hollow fiber (Asahi Medical Co., Tokyo.) was employed for the prototype. The hepatocytes which were obtained from dog were sealed into the perfusate site of the module. The metabolic activity of the module was examined by an invitro perfusion technique. The following results were obtained that oxygen was cunsumed, ammonia decreased remarkably, urea-N and glucose increased slightly, and some amino asids changed in each individual range. These support the usefulness of the module for developing a hybrid artificial liver.

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A new ammonia adsorption system was developed using silicate complex (TTY 500) and evaluated by means of in vitro and in vivo study. In vitro study evidenced that ammonia adsorption rate was 72.2%. In vivo study showed that serum ammonia in hepatic failure dogs decreased during the hepatic assist.
Direct hemoperfusion with charcoal coated by polyurethane (AAC) was carried out for the hepatic failure dogs. Satisfactory blood biocompatibility was obtained. The AAC-DHP group (4 dogs) at this prognosis was compared to the control group (17 dogs). During DHP there was significant decrease in serum tryptophan but no significant difference between both groups in survival time.

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There have been few reports of objective evaluation methods for artificial liver support due to unknown hepatic toxins and difficulties of producing reversible hepatic failure model.
It is considered that the plasma cross circulation (PCC) will be extended the evaluation method for artificial liver support observing the influence against donor's liver, because the PCC is the method to depend on the donor's liver for the antidotal and metabolic functions.
We tried to conduct the PCC for donor dogs and hepatic failure dogs using various kinds of adsorbents in order to evaluate the adsorbability of adsorbent for unknown hepatic failure substances.
Results showed high biochemical levels after the circulation until the next day, and then gradually decreasing to the normal values within 10days all most of non-treated group. However groups treated with charcoal, XAD-7 and complex system (charcoal+resin) were all normal on the forth day after PCC. Furthermore, same results were obtained by high performance liquid chromatogram of each plasma and histological findings.
Thus, prognosis of donor reveals the efficiency of artificial liver support used on PCC.

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A double filtration type artificial liver support system composed of two different sized hollow fibers is being developed as the treatment of hepatic failure in our clinic.
Our previous system had been utilized successfully for animal experiments and clinical use. Bilirubin and transaminase in serum had been reduced prominently and there were no remarkable changes in the electrolytes. However, the reduction of ammonia was not enough.
Therefore we made a new system which has a noncoating activated charcoal and ammonia absorber (AMSORBA). This model worked excellently in reduction of bilirubin and ammonia. The serum ammonia decreased from 175 to 44.3μg/dl, 75%. Only problem of this system is its complicity. Further study should be done to make this system less complicated.
In brief, our artificial liver presents the realistic possibility of evolving into a specific treatment for the management of hepatic failure.

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Plasma exchange using cellulose acetate hollow fiber (CAHF) filter has been developed and applied to patients with acute hepatic failure.
A prototype module of plasma separator, which is an improved cellulose acetate hollow fiber (Plasmaflo, PF-O2), was utillized for plasma exchange.
5L of plasma exchange was performed within 3 hrs. The concentration of various plasma proteins including HBs-Ag, HBc-Ab and immune complex in filtrated plasma was almost same as those in plasma obtained by centrifugal method.
4 out of 8 patients with fulminant hepatic failure were survived. Even in fatal cases, the prolongation of survival time was shown to be possible by daily repeated plasma exchange. The supplementation of hepatic synthetic detects appeares to be possible by intensive plasma exchanged.
However, detoxification of toxic substances with large pool size appears to be insufficient by 5L of daily plasma exchange in fatal cases.
These chinical results indicated that the daily repeated plasma exchange with hollow fiber filter is effective in treatment of acute hepatic failure.

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Recently plasma exchange have been thought effective in the treatments of collagen diseases and diseases with autoimune antibodies. We also have treated two patients with SLE, a paraquat intoxication patient, and three patietns with acute liver failure with plasma exchange.
We used fresh frozen plasma of about 3L for one plasma exchange treatment.
In result, renal function was improved in a patient with SLE.
Paraquat intoxication patient was prevented from increase of pulmonary fibrosis. But three patients with acute liver failure were died.

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The performance of new valves (c-c Björk Shiley valve, OmniScience valve, Ross valve) has been assessed in the hydromechanical simulation. Each valves hydrodynamic performance are compared at pressure gradient in steady flow, valve leakage, and difference of output in pulsatile flow.
OminiScience valve is better than Lillehei Kaster valve in all hydromechanical tests.
The performance of c-c Björk Shiley valve is almost same as Björk Shiley valve. The cusps of Ross valve is suspected to be hard to move simultaneously. At the point of leakage, there are no markedly difference between tested valves except Ross valves high profile type.
Because there are small hydromechanical difference between these valves, when we select the valve to inplant clinically, we must consider not only hydromechanical performance, but thrombogenicity, durability, and the patient life.

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St. Jude Medical cardiac valve prosthesis is a mechanical artificial valve of completely central flow type and has more favorable hemodynamic features than any other artificial cardiac valves in conventional use, e. g., Starr-Edwards ball valves. It is durable, has minimal risk of causing hemolysis and thromboembolism and can therefore be anticipated to prove great clinical value.

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The hydrodynamic characteristics of Ionescu-Shiley pericardial xenograft has been evaluated in a pulse duplicator system.
Encouraged by the good assesments, we have started a clinical application of the Ionescu-Shiley pericardial xenogragt.
60 valves have been implanted in 51 patients in the 13 months period between August 1979 to October 1980. Operative mortality was 11.8%.
The overall mean peak systolic pressure gradient in the aortic position was 13.0mmHg with the size 21mm valve and 13.0mmHg with the size 23mm valve.
The calculated orifice area in the aortic position was larger than that of the Hancock xonograft model 250.
There have been no thromboembolic episode, no valve dysfunction and no valve infection.
The hemodynamic characteristics of the Ionescu-Shiley pericardial xenograft is satisfactrily, and we will continue of our clinical use of this valve.

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Artificial valves have been successfully transplanted in valvular heart diseases by open heart surgery. The characteristics of artificial valves as stenosis was studied from view point of fluid dynamics. 23 papers published from 1966-1980 were studied which described the relationship between pressure loss and flow across the valve in in vitro experiments. The pressure loss (ΔP) and the flow across the valve was obtained from the pressure-flow curve in figures or in the tables from these papers. The velocity was calculated from flow and external diameter (D) of the valve. Pressure loss coefficient λ was calculated using the following equation. λ=ΔP/1/2ρU²where Δ² P is the pressure drop (dyn/cm²), ρ is fluid density (g/cm³) and U is the flow velocity (cm/sec). Pressure loss and velocity was obtained from 3 different points at the same curve.
The shape of artificial valve was assumed to be like an orifice in a pipe. The relationship between the pressure loss coefficient λ and the cross-sectional area ratio (total occlusion, 100%) are commonly known for the orifice.
Cross-sectional area ratio of artificial valve was derived from pressure loss coefficient λ. The average value of crosssectional area ratio of stenosis was 58 (54-64)% in artificial valves. The value in xenograft (Hancock) valve was 63% and was not so small in comparison with other mechanical valves.

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Six prosthetic valves have been assessed on the hydraulic efficiency and dynamic performances. Evaluation parameters are the Pressure Gradient at steady flow, and the Energy Loss and the Performance Index at pulsatile flow. H-K valve had the best hydrodynamic efficiency among the valves tested.

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This study was made as the basic research for the developement of the new tri-leaflet valve prosthesis in aortic position. On the basis of the analysis of the opening characteristics of normal aortic valve, non-stented tri-leaflet valve prosthesis was produced with polyether-urethan-urea. The basic geometry of the leaflet is the ellipsoid of revolution. The optimum tilt angle of the free margin of the leaflet was studied through stress analysis and hydrodynamic simulation. From the result of this study, it became evident that non-stented trileaflet valve should have a tilt angle at 20 degree, and it seems to be one of the fundamental parameters of the leaflet geometry.

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In this study, a new type of flexible stented tri-leaflet valve (FSV) was designed, constructed and tested under the steady flow as well as pulsatile flow conditions in a mock circulation system. Flexible stent was made of 1.3mmφ spiral spring of which material was 0.3mmφ stainless steel wire. Polyurethane leaflets were produced by the dipping method and sewed up on the Dacron cloth-woven stent. Functional evaluation of the valve was carried out on the following terms; a) Flow rate v. s. pressure gradient characteristic, b) Leakage flow at 100cmH₂O, c) Performance index at the steady flow, d) Systolic energy loss, e) Diastolic energy loss and f) Performance index at the pulsatile flow, and compared with the same size and the same form of rigid stented tri-leaflet valve (RSV). FSV showed the increasing of valve area and the better forward performances at high flow rate than RSV because the flexible scent extended outward on the aortic wall. Leakage flow of the valves showed to be less than 7.5cc/s, which did not depend on the type of stent and the orifice diameter but only on the quality of the leaflets manufactured. In any case, the high efficacy of the flexible stent was observed, which gave some suggestions concerning with the development of stented Xenograft valves.

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In heart valve replacement, a prosthetic valve is often sutured to the annulus with the deflection angle between valve axis and flow axis, because of the deformed annulus. The present study will describe our results of hemodynamic tests regarding pressure gradient characteristics, as prosthetic valves were tilted with deflection angle.
Three types of prosthetic valves (i. e. Carpentier-Edwards (CE) valve, Björk-Shiley (BS) valve, and St. Jude Medical (SJM) valve) were compared. Pressure gradient of the CE valve was much greater than the other two types of valves. When the right coronary cusp of the CE valve was directed to flow axis (≤20°), the pressure gradient significantly decreased. As the BS valve had a tilting disk, the pressure gradient was significantly changed by the direction (≤20°) of tilting disk. The SJM valve exhibited about 30% lower pressure gradient than the BS valve. In contrast with the other two types of valves, deflection (≤20°) of the SJM valve axis had no effect on pressure gradient. These hemodynamic differences were considered to be caused by their mechanical structures. In conclusion, we have found that fluid dynamic tests with the deflection of valve axis from the flow axis was very useful to evaluate hemodynamic properties of the prosthetic valve.

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Flow characteristics of five types of prosthetic valves were evaluated with pulsatile flow.
Valves tested were the Starr-Edwards valve, the Björk-Shiley valve, the Hall-Kaster valve, the S. J. M. valve and the Hancock xengraft.
Aluminium micro-leaves were mixed into the water of the pulse duplicating system. Flow characteristics of the valves were observed and photographed in each phase by 16mm movie and 35mm black and white film.
The Starr-Edwards valve caused extensive stagnation of flow.
The Björk-Shiley valve and the Hall-Kaster valve produced turblance flow with similar direction. The stagnation at the small aperture side of the Hall-Kaster valve was smaller than that of the Björk-Shiley valve. The S. J. M. valve showed two stagnation near the central portion arround the hinge. The Hancock xenograft showed central jetting flow and the stagnation caused by the cusp.

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In this study, a new type of fan-shaped trileaflet prosthetic valve was designed, constructed and tested under the steady flow as well as the pulsatile flow conditions in a mock circulation system. The new valve is composed of an orifice ring, three semicircular leaflets, three supporting pivots and an annular cuff. Annulus diameter and orifice diameter of the valve are 30mmφ and 24mmφ respectively. Hydrodynamic evaluation was carried out on the following terms; a) flow rate v. s. pressure gradient characteristic, b) leakage flow at 100cmH₂O, c) performance index at the steady flow, d) systolic energy loss, e) diastolic energy loss and f) performance index at the pulsatile flow. These characteristics were compared with those of Bjork-Shiley valve (29mmφ annulus diameter) and Starr-Edwards ball valve (30mmφ annulus diameter). Results of the steady flow (Q) v. s. transvalvular_n pressure gradient (ΔP) for the tested valves were represented by the relationship of ΔP=kQ and n was almost 2. Coefficient k corresponding to the flow resistance was 0.014mmHg. (min/L)₂ for the new valve, but were 0.008 for B-S valve and 0.024 for S-E valve. The forward performances (pressure gradient, systolic energy loss and performance index) of the developed valve show the fairly good characteristics among the valves tested, but relatively much leakage flow can be observed, which results in the more diastolic energy loss. Improvement of the valve, especially on the close contact of the leaflets, will give the acceptance of the in-vivo application and clinical use.

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An evaluation was carried out of twelve consecutive patients undergoing combined aortic and mitral valve replacement.
Combination of cold cardioplegia and intrapericardial cooling mat was used for myocardial preservation during ischemic arrest. Such Combination bring the septal temperature to near 10°C and keep low temperature of 7-15°C effectively. The Cpk-MB level was slightly high in this group as compared AVR or MVR group., Two operative death did not correlate with this myocardial protection. Postoperative course of another ten patients was satisfactory. The results of this study support the safety of prolonged cardioplegic arrest under low myocardial temperature in combined aortic and mitral valve replacement

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High Sodium Dialysate Technique is important in order to increase mass transfer from peripheral tissues into plasma. A high sodium dialysate technique maintaining sodium balance has been developed. It has been called CELL-WASH DIALYSIS (CWD). For the first period of 45-60min, a 180-200 mEq/L sodium dialysate concentration is used and the sodium concentration is then lowered to a concentration of 130-140mEq/L. These two levels of sodium concentration are used alternately. Clinical results of the treatment with CWD are: (1) loss of basal body weight, (2) disappearance of general fatigue, (3) elimination of hypotension during dialysis, (4) increase of appetite, (5) increase of microcirculation, and (6) acceleration of protein synthesis.

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In chronic hemodialysis (HD) patients, hemodynamic and clinical effects of HD with acetate containing dialysate were evaluated and compared with those of HD with bicarbonate containing dialysate. In the end of HD with the acetate dialysate, an increase in the limb blood flow, a decrease in total vascular resistance, a fall in mean BP and a rise in PEP/ET ratio were observed significantly. This vasodilating effect was not found after HD with the bicarbonate dialysate. A vasodilating effect and a rise in PEP/ET of acetate were comfirmed in the infusion test, too. Following infusion of sodium acetate, a significant fall in arterial PO² was also observed. Side effects, such as hypotension, nausea and vomiting, discomfort of the chest, and abdominal pain, observed frequently during the acetate HD were significantly improved by the bicarbonate HD.

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For the past four years we have been studying the clinical effects of hemofiltration (HF), and found out that HF treatment is quite effective against dysdialysis syndrome, since solute kinetics of HF, quite different from that of hemodialysis (HD), induces physiologically more natural mass-transfer between the body fluid compartments.
Chronic renal failure is expressed as all kinds of metabolic disorders. Therefore, efforts to improve such metabolic disorder should be studied in order to evaluate the effects of HD and HF. We have already reported that in HF patients, generation rate of urea as well as that of guanidinosuccinic acid and methylguanidine were lowered. Not only blood concentration but also intercellular concentration of the latter two compounds were significantly lowered when compared with HD patients. It was suggested that HF has better effect on protein and amino acid metabolism. In the present study, the carbohydrate metabolism which is indispensable to the maintenance of cell life is investigated.
6 patients each from HD and HF with averaged 30 month treatment and 6 normal volunteers were selected and comparison was made between the 3 groups. Their body weight was within 2.5% range from the standard and subject with diabetes mellitus was excluded.
0.5/kg of intravenous glucose tolerance test (ivGTT) was started from 9A.M. on these 3 fasted groups. Blood sugar and immuno-reactive insulin (IRI) were measured at regular time interval.
There was no significant difference in blood sugar curve between 3 groups. K value of HD and HF groups as the result of ivGTT were 1.5±0.31 (M±S.D.) and 2.6±1.11, respectively, which showed no significant difference. However, in the serum IRI level, HD group showed significantly higher value (P<0.05) at 3, 10, 20 and 30 minutes after glucose load. The insulin/glucose ratio was also significantly high at 20 and 30 minutes in HD group.
The tolbutamide loading test showed no significant difference in the insulin secretion responsiveness between 3 groups.
In conclusion, the carbohydrate metabolism disorder in the end stage of chronic renal failure seemed to have been improved with insulin over-secretion by hemodialysis therapy. However, insulin sensitivity and glucose utilization in the peripheral, target organ and cell was shown to be more improved in HF treatment than in HD.

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We evaluated three different blood cleansing methods (hemodialysis, hemodiafiltration and hemofiltration) from clinical points of view.
1) At first, we checked up many parameters (WBC counts, platelet counts, serum complement, coil planet centrifuge pattern and serum β-thromboglobulin) in the biocompatibility. We obtained good biocompatibility in all methods.
2) Changes of plasma volume during hemofiltration was less than that during the other methods.
3) Sequential decrease of the intraocular pressure was observed in hemofiltration process. But only small changes were seen in the other methods.
4) There was positive correlation between blood pH and tissue pH. There was slight difference between blood pH and tissue pH in hemodialysis and hemodiafiltration. But no difference was observed in hemofiltration. From this result, it may be suggested that metabolic acidosis was corrected in the extra- and intracellular space at the same rate in hemofiltration.
Further study will be nessesary for us to come to a conclusion which method is the best.

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As of October, private charges of chronic dialysis were covered by the government, therefore, number of chronic dialysis patients have significantly increased by year and year, and this tendency of increase is still kept in Japan. At the end of 1979, there were 32, 331 patients treated with chronic dialysis.
Number of patients required to blood purification are increased among chronic renal failure as well as acute renal failure, acute hepatic failure, detoxification and so on. Therefore, new device not depending upon dialysis is desired. We have developed hemoperfusion system combining in 1974. Since then, many clinical cases of chronic renal failure, acute renal failure, acute hepatic failure, detoxification and psoriasis were done in our clinic.
I. For chronic renal failure as chronic dialysis.
1. Short time dialysis:
This system is able to maintenance chronic dialysis patients treated with 5-6 hrs. hemodialysis to only 3 hours treatment.
2. Decrease of dialysis freqency:
This system can easily decrease dialysis freqency in one week from 3 times to 2 times in 4 patients during a half year.
3. Uremic pericarditis
The period of healing uremic pericarditis is significantly reduced by this system compared with ordinary hemodialysis.
II. For acute renal failure.
This system is applied for as an artificial reticuloendothelial system in the treatment of acute renal failure. The survival ratio of acute renal failure is significantly increased by this treatment compared with hemodialysis. (n=33)
In conclusion, this sytem of blood purification with hemoperfusion and hemodialysis simultaneously is very usuful for the treatment of chronic renal failure as well as acute one.

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In the 58 months from January 1, 1975 to October 31, 1980, 23 patients required assisted circulation pre- or past-cardiopulmonary bypass. Six patients (268) were successfully weaned from the assisted circulation and survived.
Veno-arterial bypass (VAB) without intraaortic balloon pumping (IABP) was performed in 15 patients, and it was effective in 3 patients. In two of them, the cause of low cardiac output was removed surgically after VAB and a patient with intractable ventricular fibrillation which occured in ICU was defibrillated under VAB.
Eight patients who showed myocardial injuries after open heart surgery or coronary revascularization underwent VAB and IABP and only three patients demonstrated adequate responses and survived operation.
These data suggested that VAB with IABP might be ineffective for patients who had severe myocardial injuries after cardiopulmonary bypass and we expect the left ventricular assist device will offer a great help in these cases.

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In this report, pulsatile air driven systems will be written. Because most of blood pumps for clinical use are air driven type and their driving mechanisms are usually composed of electromagnetic air valves and air pressure regulators. Positive/negative air pulses are generated from compressed air and vacuum air. The driving machine for clinical usage has three main points of arguments as follows.
1) DRIVING SYSTEM; As temporal usage of assist heart is today's clinical consensus, air driven system is the best choice from its controllability and its stability. In order to respond to the dynamic change of circulatory system, ECG synchronization and measurement of pump output are essential factors for controlling the driving system. Various kinds of driving mechanism and also various kinds of measurement method of pump output are developed today.
2)LOAD OF PUMP OUT; AT the temporal usage of assist device, the cannulation site and orifice and length of cannulae are decided most of the performance of the assist heart. The conventional cannulae for cardio-pulmonary bypass have very high internal hydraulic impeadances and if the cannulae orifice are less than 6mm at 41/min pump output, the driving positive pressure exceeds 300mmHg. Then, the hydraulic bench top test of the system must be essential before clinical application.
3)PERIPHERAL ARTERIAL RESISTANCE; AT clinical usage, the patient is usually inject many kinds of peripheral circulatory drugs. The controllability of circulatory system is completely diminished. Then, we must decide the total course of control procedure of driving parameters.

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We have been developing an air-driven, diaphragm type partial artificial heart (PAH). Using this PAH, the effects of left heart bypass (LHB) from left atrium to descending aorta on failed heart were studied. The results were as follows;
1. For the left ventricular failure (LVF), LHB increased bypass flow automatically according to the severity of LVF, and consequently maintained blood pressure and total blood flow at a reasonable level. For the LVF combined with right ventricular failure (RVF), general circulation was maintained by LHB alone, but for the LVF with moderate or profound RVF, it was needed to keep right atrial pressure higher. For the case with high pulmonary vascular resistance, however, both right and left heart bypasses were needed.
2. LHB well decreased left ventricular work load, especially decreased an extent of local over-extension appeared in the ischemic area.
3. LHB increased total coronary blood flow up to normal level. In the case of myocardial infarction, LHB increased regional blood flow at the boundary of ischemic area.

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A 51 years old woman, who was in low cardiac output syndrome after mitral valve replacement and superimposed technique using the porcine bioprosthetic valve for tricuspid regurgitation, was supported by prolonged veno-arterial bypass (VAB), IABP and partial artificial heart (PAH).
The circulatory assistance by left ventricular bypass using PAH was the first clinical experience for us.
She could not be successfully weaned off from PAH assistance during 52 hours, but we have observed that PAH is the powerful assist device for supporting the failing heart after cardiac surgery.

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In May 1980, biventricular bypass (BVB) was tried in a patient whose cardiogenic shock was not recovered by use of VA bypass utilizing pump oxygenator and IABP in Mitsui Hospital in Tokyo. 52 hours' left ventricular bypass (LVB) was continued with wean-off of VA bypass, IABP and right ventricular bypass and terminated due to peripheral vascular disorder.
LVB and BVB were effective for failing heart assistance, however earlier application was appreciated.
Application on LVB and BVB---patient conditons, hardware preparation, operations software and requirements in hospital were discussed in this paper.

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As a series of integrated studies on mechanical behavior of materials for use in cardiac prostheses and their design, static and dynamic mechanical properties of five kinds of candidate elastomers are evaluated by uniaxial tests at room temperature in air.
Avcothane 51 (AVD), which is an Avco's copolymer of polyurethane and silicone, has an unstable mechanical properties under cyclic loading and gradually stiffens by the dynamic deformation. Although Hexsyn (GOP), Goodyear's polyolefin rubber, is fairly stable and highly flexible under the dynamic condition, its strength and ductility are relatively low compared with those of the other materials. Texin (MUP), Mobay's polyurehtane, has highest elastic moduli under the static and dynamic conditions. As compared with these three materials, Biomer (EBB), Ethicon's polyurethane, and Toyobo's segmented polyether polyurethane (TBU2D) have high flexibility, strength and ductility, and their mechanical properties are very stable under the cyclic loading condition. It is concluded from the mechanical point of view that these two materials are acceptable for flexible components of cardiac prostheses.

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In this paper, antithrombogenic surfaces were reviewed, and especially the role of hydrophilic-hydrophobic microphase separated surfaces in polymer-blood interaction was discussed. On the basis of the results obtained from the study on polymer-platelet interaction, we propose that the factor of balance between hydrophilicity and hydrophobicity in macromolecular assembled order is most important to design antithrombogenic polymers.

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Despite of fixed rate pumping, the animal can be alive with total artificial heart for several months. This results suggests that no responce with the change of the venous return seems to be important, particularly on the right side heart.
In other words, the easier way to keep the animal to be alive with total artificial heart may be to cut off the roop of the circulation at the right side heart between the pulmonary artery and the right atrium.
Under these conditions, it is not important whether the natural heart is removed or not, but following characteristics are only required.
1) air-driven sack type pump, or such characteristics.
2) no thrombus formation inside the device.
3) no problems at the natural heart-artificial heart junction.
These conditions are also saticified in our device as others reported so.

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This paper mentions methodological aspects of system control theory and real-time computer control applied to control problems of artificial hearts. A design of an experimental tool for artificial hearts is proposed, based upon computer control synthesis. This tool will enable users to control precisely hemodynamics and to process the data in a systematic fashion.

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To establish the control method of total artificial heart, is one of the most important problems to be solved for clinical use of total artificial heart.
In this paper, the control methods of TAH which are used in many institute, are introduced briefly, and how to establish our TAH control method is described. And finally, what factors are most influential for farther developement of TAH control method is analyzed.

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Essential requirements for automatic control system of total artificial heart are to balance the 2 pumps and to increase cardiac output when required by the body. Intrinsic control system balances 2 pumps and increases outflow as a function of filling pressure without sophiciticated control device. However, cardiac output by this method is inadequate because outflow increases only by onetenth as much as the natural heart. Extrinsic control system via aortic pressure, atrial pressure, mixed venous oxygen tension or p-wave in the remnant atrium provides more adequate cardiac output. However, the obstacle of this method is lack of a stable, reliable and implantable pressure or blood gas transducer. To overcome the current problems the following control systems are proposed: (1) Intrinsic control system for an implantable pump and external drive unit. Intrinsic control system only is enough for the patient with restricted activity by a drive line. (2) Extrinsic control system via p-wave or blood volume in the pump for an implantable pump, drive system and sensor. Extrinsic control policy should be included to meet patient's greater activities enabled by totally implantable system. P-wave and blood volume in the pump can be measured by the current technique.

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The average survival times of calves with total artificial heart (TAH) has been prolonged because of the effective infusion or adaptation of technologic advances in a wide variety of disciplines, including biomaterials, engineering, heart manufacturing, surgical implantation, and animal management. However new hemodynamic problems have appeared in proportion to prolonged average survival with TAH. Many basic researches have been continuing to eliminate these problems. The following points of circulatory maintenance in calves with TAH have been discussed in this manuscript.
I. Appropriate cardiac output in calves with TAH
II. Monitoring the function of TAH
III. Hemodynamic problems
a) high right atrial pressure
b) inflow obstruction caused by pannus or thrombus
c) outflow obstruction caused by thrombus or granulation tissue
IV. Mechanical failure
a) pin-sized hole in the diaphragm
b) emigration valve and broken valve
c) air leakage from the driving tube

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The management for the circulatory systems after total artificial heart replacement is very simple. We are using Utah heart driver systems. Both sides of air drive-line pressure waveform should be monitored in all cases.
The driving parameters of the heart driver are ajusted to the optimum by watching the monitor ing these air-driving pressure waveform and we can perceive abnormal changes of the driving systems including inside the heart from these pressure waveforms.
Eight calves were replaced with total artifici al heart in our department and one calf surviv ed 15 days after surgery. Recently we are using Japanese artificial hearts which made in Tomasu Technical Company in Himeji. One calf with Tomasu Heart died on the 9th day after surgery due to air leakage from the ventricle and there was no thrombus formation inside the heart at necropsy.

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Today I would focus of this presentation to the problems related to the artificial heart in consideration of present status and future application to human. Since the factors related to the survival of animal replaced with TAH could be defined into severals, the following three major problems are now significant in consideration of clinical application. They are calcification, tissue overgrowth and high venous pressure. However, all of these three complications could be overcome by individual technical management, although they are not really ideal stage of research. Thus I could define positive and negative factors for the clinical application of TAH. The negative sides are including public attitude, standardization of medical device and lack of back up procedures or techniques, decreased incidence of cardiogenic shock, etc. For the positive side, I could point sufficient numbers of candidates, and reliability of the system at least for about 60 days of survival of the animal, etc.
Thus we are now in stage of clinical evaluation in limited trial. For example our research in Hiroshima University are concentrated to 1) the intermittent demand type use of assisted heart for myocardiopathia, 2) combined and alternative use of TAH and cardiac transplantation.
In the last the lack of adequate experimentation with use of experimental models of cardiac failure is one of the major concerns which we should focus in the next stage of the artificial heart research.

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The definition of total artificial heart (TAH) means the mechanical pumps to replace natural heart functions completely without consideration on the shape, the size and the installed position.
In the August of 1979, 29 TAH animals survived over three months in the world
In 1980, in Tokyo University 11 TAH goats survival over three months---including 288 days, 243 days and 232 days---.
The longest survival (288 days) died by the human error of switching the driving systems. In this case, no clotting in the cannula and pumps in spite of no anticoagulant use.
In future, three types of TAH---bedside, wheel chair and implantable---will be designed and developed.

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