IABP, which is one of the procedure for mechanial assist circulation, has been. used in the management of cardiogenic shock. In our experimental study, we performed IABP for 2hours in normal dogs and ischemic heart dogs, and determined arterial pressure, A. carotis interna pressure and flow, Sinus sagital superior pressure and cerebral circulation time.
The result of experimental study, cerebral perfusion pressure was sustained but cerebral vascular resistance was increased.

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This study was aimed to investigate the effect of intraaortic balloon pumping (IABP) and left heart bypass (LHB, 30% bypass flow of cardiac output) for cardiogenic shock in mongrel dogs with acute myocardial infarction (AMI) following multiple ligation of the coronary arteries. Subsequently, an increase of 33% in diastolic aortic pressure and 38% in cardiac output, and a fall of 33% in left ventricular enddiastolic pressure were obviously obtained after 120 minutes with initiation of IABP.
The value of EVR (DPTI/TTI, supply-demand ratio) increased from 1.00 to 1.22, and lactate extraction also increased from 9% to 24% during IABP for 120 minutes. From above findings, hemodynamics and myocardial metabolism could be improved by IABP. On the other hand, in comparison with IABP and LHB in the hemodynamics and myocardial metabolism, LHB could not improve these findings than that of IABP. It can be considered that bypass flow rate depends on the improvement of those findings. In conclusion, when the value of EVR fell under 0.7, lactate extraction disclosed negative value, which indicated inadequated subendocardial perfusion with poor prognosis because of progression of anerobic myocardial metabolism in the ischemic myocardium.

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The effects of left ventricular bypass rate on myocardial metabolism after coronary occlusion were examined by measuring myocardial oxygen (Pmo2) and carbon dioxide tension (Pmco2). Findings were: (1) In total bypass group (5 dogs) Pmco2 increased slowly (90% response time 49min) and reached a maximum of 191±59mmHg above control. In partial bypass group (5 dogs) Pmco2 increased moderately fast (90% response time 23min) and reached a maximum of 102±18mmHg above control. In no bypass group Pmco2 increased fast (90% response time 15min) and reached a maximum of 51±12mmHg above control. (2) Pmo2 gradually decreased to 25±6mmHg below control in total bypass, 21±2mmHg below control in partial bypass and 8±1mmHg below control in no bypass 60min after ligation. The results indicate that larger degrees of bypass are required to maintain cellular viability because anaerobic metabolism was becoming inadequate in a shorter time in partial bypass group than in total bypass group.

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One hour of ECC with perfluorochemical emulsion (FDA) was performed in 5 calves. Approximately 5.3 L of FDA was used for priming solution and 10.9g/kg of FDA was retained in the body after ECC. The lowest hematocrit was 8.2% on the average and PaO₂ was remained approximately 400mmHg during perfusion. There was no remarkable change in electrolyte and blood osmorality in Whole experiment. Three of 5 calves are surviving in excellent conditions. Blood chemistry in these animals showed normal values after surgery. Liver biopsy for histopathologic exami nation were performed on 12th, 40th, and 60th day of surgery in a calf. Foam cells in the liver tended to reduced gradually in the course of time.

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In western countries brain death has been approved, however, in Japan it has not been approved yet. In Japan death is defined as ccomplete cessation of heart beat. So that, prolonged warm ischemic time must decrease the viability of the graft. To overcome this disadventage, we devised a new preserving method using specially inverted machine, arterial and venous canulae and artificial blood (Fluosol-DA). We were succeeded in two cases of cadaveric renal transplantation using this method.
A donor who died of subarachnodal hemorrhage was a 52-year-old male. Sventeen minutes after cardiac arrest, arterial and venous canulae were inserted via femoral artery and vein the pushed up to the abdominal aorta and inferior caval vein. Balloons were inflated and intracadaveric perfusion was started.
Renal transplantation in two recipients were finished 5 hours and 3 minutes after cardiac arrest. Nephrectomy performed under this perfusion. Renal functions showed normal values 27th and 37th days after transplantation in these cases.

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Computer algorithm for self-adaptive control of blood glucose has been established.
With this algorithm, parameters deciding insulin infusion rate are automatically changed in accordance with insulin sensitivity index of the subjects calculated from the difference between the measured rate of change in blood glucose and the projected rate of change in blood glucose.
The validity of this algorithm was recognized in animal experiments using depancreatized dogs.
Artificial endocrine pancreas with selfadaptive algorithm is useful not only as the management of diabetics but also as the elegant research tool for the investigation of insulin sensitivity of the diabetics or. analyzing the blood glucose regulatory mechanism

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Glucose sensor for implantable artificial pancreas has been developed in our laboratories. Our new structure of the sensor shapes a vessel access and has a special membrane which passes glucose partially in the blood inside it. This sensor is able to response to glucose levels up to 700mg% without dilution and the response time is six minutes. The activity of the immobilized enzyme membrane decreases minimum about 4% within three mounths and does not change with an intermitent use for 50 days.

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The new glucose sensor which shapes a vessel access and is able to measure the blood glucose level directly in blood has used experimentally in a dog. An external vessel access is made between internal carotid artery and external jugular vein on the neck of dog.
The glucose sensor is set in a vessel access through which the artery blood flows. The sensor responses to the blood glucose levels in six minutes after loading glucose intravenously. However, it takes about 20 minutes to response to the blood glucose levels in decrease following the administration of insuline.

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We had developed the optimal control system of blood glucose level as a new artificial betacell, and reported previously. We employed quadratic linearized model proposed by Ackerman as the mathematical model of the blood glucose regulatory system in the human body, and applied for the first time. However, as we reported, it is necessary to estimate the parameter's value of this mathematical model correctly to perform the optimal control.
In the second report, we had tried to adopt the recursive least squares parameter estimation procedure to estimate the parameter's value, and in this study we have improved this algorithm to develope the stability and the ability of the parameter estimation procedure. We have carried out not only the digital simulation but also the animal experiments with diabetic dogs and confirmed that this procedure could estimate the parameter's value satisfactorily.

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We have developed an artificial endocrine pancreas in which computer algorithms for insulin and glucose infusion and self-adaptive control. The characteristics of the programs is that insulin or glucose is infused to simulate plasma concentrations of insulin or glucose exactly the same as those seen in normal subjects. So, this system is considered useful not only for clinical applications, but also as an elegant research tool. In this communication, the usefulness of the system in investigating the normalization of abnormal glucagon secretion in diabetics, blood glucose regulations in insulinoma patient during insulin provocation test and operation and the adaptive blood glucose regulation in ketoacidotic coma patient, were reported.

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As a new biologic substitute for small artery, we have evaluated Reserved Human Umbilical Artery (RHUA), which is stabilized with 1.2% glutaraldehyde and has a diameter of 2.8 to 3.8mm. The RHUA with 6.5 to 7cm length were implanted in the carotid (15 grafts) and the aorto-iliac (2 grafts) artery of dog. (mean weight of 14.5kg). In the group of carotid artery replacement, seven (12 grafts) of 9 dogs were sacrificed at the intervals ranging from 7 to 13 days and remaining 2 dogs (3 grafts) are still alive with patent graft at the present time. Six of 15 grafts were occluded, resulting the patency of 60%. One of 2 aortoiliac bypasses was occluded. Blood coagulation time was estimated before implantation using Hemocron 400. Blood flow was also measured 30min after implantation. These were varried from 22 to 230ml/min. All six grafts more than 100ml/min were patent. In comparing the patency rate with graft flow and blood coagulation time, four of 10 grafts less than 100ml/min were patent showing relatively longer coagulation time. It is suggested that coagulation time has great inflnence on graft patency in low flow range. The patency rate of 60% in carotid artery replacement of dog suggests that the RHUA may be usefull for reconstruction of small artery. As the other application of the RHUA, we are going to study aorto-coronary bypass in dog. Now we have a initial success for aorto-left coronary (circumflex) bypass of dog (Weight of 18kg) emploing our modified intraluminal shunt procedure. This might be promising further study of coronary artery reconstruction using the RHUA in dog.

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Experimental examination of Human Umbilical Cord Veins (H-UCV) as a vascular substitute was started at 1969 in our department. Since 1975, clinical applications of Glutaraldehyde (GA)-tanned H-UCV as a arterial substitute are going on.
41 peripheral arterial vascular reconstructions, in 39 patients, were performed. Up to date it's cumulative patency rate is 92.6% at one year, 88.2% at two years and 81.9% at 3 and 4 years.
On the other hand, since 1977, Equine Umbilical Cord Vessels (E-UCV) were investigated as a larger sized material than 6mm in diameter.
Fundamental evaluation demonstrated it's many good points, that is optimal elasticity, high tolerance to inner pressure, good antithrombogenicity and large caliber.
As a vascular substitute, especially as a venous substitute, GA-tanned E-UCV transplantations into venous system have been studied.
Antigenicity of H-UCV and E-UCV was evaluated with delayed hypersensitivity skin reaction, which reflects cell-mediate immunity well and lyphocyte blast transformation. It was revealed that antigenicity of H-UCV and E-UCV was gratifyingly suppressed by GA-tanning.
Results of immunological examinations and GA-tanned E-UCV transplantations for venous reconstruction of mongrel dogs are presented in this paper.

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Human umbilical cord veins (HUCV) treated by 5 different tanning methods were implanted in the aorta of dogs to evaluate the optimal concentration of glutaraldehyde and ethanol, patency, morphology and antigenicity.
The following results were obtained: (1) tanning with 0.5% glutaraldehyde for 24 hours and preserving in 50% ethanol is the most useful method. (2) Its overall patency rate was 85% (34/40). (3) The structural integrity of the graft was well preserved with minimal host cell ingrowth. (4) The inner surface was covered by fibrin, in which endothelial cells appeared near the suture line. (5) cytotoxic tests suggested that antigenicity was effectively suppressed.
Two other kinds of grafts taken from pig and human cadavers were tanned with 0.5% glutaraldehyde and preserved in 50% ethanol. These grafts were implanted in dogs in the same manner.
The results as follows: (1) Patency of both these grafts was inferior to that of HUCV. (2) Host cell reaction was significant, especially in the adventitia.

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The saphenous veins from varicose patients were strong enough to use as modified human saphenous vein homografts and their structure were not so different from those of cadaveric saphenous veins. 24 homografts, first halves were untreated with ficin, the other halves were treated, and all tanned with 1.5% glutaraldehyde, were implanted in the abdominal aorta of dogs.
10 grafts of untreated group and 11 grafts of treated group were patent in 3-365 days follow up. The inner surface of an untreated cadaveric saphenous vein graft implanted one year ago was smooth, and there was not cell infiltration, any destructive findings microscopically. Glutaraldehyde tanned human saphenous vein will be a good substitute.

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The pig ureters treated with ether andglutaraldehyde were experimentally evaluated in order to develop the small caliber arterial prosthesis.
They were implanted in the canine ileofemoral or femoral positions.
As a result, the excellent results were obtained as regards patency rate. However, the histological studies revealed the marked degeneration of intrinsic muscular fihers of the graft 6 months after implantations. Therefore, it was considered that the tensile strength of these grofts was maintained only by residual colloyen fihers In the mucosal propria of the ureter. Long term observations should be needed to determine the further change in the strength of the graft.

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1) Clinical studies on 91 bovine grafts performed from December 1976 through April 1978 in Dept. of Surg., Univ. of Munich were presented.
2) On the other hand, follow-up studies at 1 to 5 years postoperatively for the 247 patients who had had bovine grafting between 1974 and 1978 in the same hospital were also carried out.
3) On the basis of these studies, bovine grafts for the reconstructive vascular surgery were reviewed and following conclusions were obtained.
a) Bovine graft was used mainly as femoropopliteal bypass for the cases without available or adequate autogenous vein graft.
b) Both the short term and the long term results were excellent. Incidence of occlusion of bypass was only 10.7% in the former and 29.1% in the latter.
c) In the short bypass above the knee, occlusion rate was 28.1% until the time of last follow-up and it was markedly lower than that of the long bypass below the knee, 52.6%. It suggests that the bypass procedure across the knee joint should be restrained. The composite graft (bovine plus autogenous vein) were often available in these situations and good results were obtained.
d) Patch graft operation was also carried out with bovine graft and very good results were obtained and it seems to be useful for reduction of operating time.
e) Aneurysms in bovine grafts were noted in 3.1% and seemed to occur more often than not later and this controversial problem is also discussed.

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In vitro adhesion and deformation of the platelets on the surface of the medical polymers has been evaluated by scanning electron microscopy. The four polymers evaluated were polyethylene, teflone, silicone rubber, and H-RSD (heparinized hydrophilic polymer). Approximately 0.05ml of platelet rich plasma freshly prepared from the normal healthy adult was dropped on the surface of the catheters made of these polymers (5mm in diameter), and the specimen for scanning electron microscopy were made at 15 and 30 minutes. Number of platelets adhered to the surface and their deformation after adhesion to the surface have been studied.
Number of platelets adhered to the surface of polyethylene at 15 minutes were 469/1.4mm² and 1192/1.4mm² at 30 minutes. On the surface of teflon, 176 platelets were observed at 15 minutes and 488 at 30 minutes whereas on silicone rubber, 172 and 319 platelets were observed at 15 and 30 minutes respectively. Number of platelets adhered to the surface of H-RSD was much less and only 78/1.4mm² at 15 minutes and 70/1.4mm² at 30 minutes.
Deformation of the platelets after adhesion to the surface was most severe on polyethylene, moderate on teflon and on silicone rubber, and very slight on the surface of H-RSD.
Adhesion of the platelets to the surface of the polymers and their deformation are the initial steps of thrombus formation on the polymers. H-RSD is the least thrombogenic material and polyethylene is the most thrombogenic material of the four polymers evaluated in this study.

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In this study, the thrombus formation on the surface of silica free silicone tube (SFST) and medical grade silicone tube (ST) was investigated by implanting in the arterio-venous shunts in dogs. The inner surface of the tubes were observed by the scanning electron microscopy and fluorescent labeled antibodies stainning, after the removal from dogs.
The results showed that the adhesion of platelets and deposition of proteins on the surface of SFST were lesser than those of ST. And platelets adhered on the surface of SFST had a few false feet.
The experiments suggest that the good blood compatibility of SFST is largely attributable to the suppression of platelet deformation.

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Distribution of the radioiodinated human fibrinogen in the rat which was implanted the biomedical materials in the vena cava (through jugular vein) was investigated with the use of autoradiographic techniques.
Our studies indicate that autoradiography with radiolabeled fibrinogen has substantial promise as a means for detecting the presence of fresh venous thrombi on the surface of the biomedical materials.

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The majority of currently available in vivo antithrombogenicity test have a definite drawback in assessing the true antithrombogenicity of the test material itself, because the continuous contact of inserted test material with the cardiovascular inner surface may initiate thrombus formation over boundary zone between test material and the intima.
Therefore, we developed new in vivo material test-atrial floating ring test-to avoid the continuous contact of test material to the intima and to evaluate the real antithrombogenicity for prosthetic implants.
In our mathod the test material (coated on prosthetic ring) was implanted in canine right or left atrium and kept floating inside.
In this report 2 groups of polymer material-silicon and polyurethane were evaluated for its thromboresistance using our material test. The macroscopic evaluations of surface characteristics of test materials and its qualitative and quantitative analysis of surface adsorbed protein were done by S. E. M. observation and the electrophoresis.
Results:
1) The weight of surface adsorbed protein in the polyurethane group was more than that of silicon group and in addition, thrombocyte adhesion on the polyurethane surface was more remarkable than on silicon surface.
2) The thrombocyte initially adhered to the surface disappeared within 3 days after insertion in both polymer groups.
3) In poorly adsorbed protein cases electrophoretic pattern showed a peak which was identfied as albumin fraction, and as the adsorbed protein increased the electrophoretic pattern became simulated to that of so called early stage of thrombus membrane on vascular prosthesis. These data suggest that the characteristics of polymer surface is modified by not only serum protein but also blood-cell-destroyed-products even in early phase after contact with blood in vivo.

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To investigate influence of electric charge on thrombus formation on the luminal surface of the prosthesis, a vascular prosthesis which made of electroconductive materials was placed in the inferior vena cava of the dogs. A large amount of coagulation was formed on the positive-charged luminal surface, whereas few amount coagulation was formed on the negative-charged surface. And the non-charged that is electroconductive surface showed similarly anticoagulant effect.
In examining with SEM the process of neointima formation in implanted vascular prosthesis, it appeared that constructed fibrin matrix layer prevented futher adhesion of blood cells and the platelets adhered and covered only the incomplete areas of fibrin matrix formation. These phenomena of forming fibrin matrix seem to reduce the positive charge and may even make luminal surface negative.
In vitro experiments using platelet-rich plasma, it was shown that only a few platelets with slight deformation were adhered to the negative-charged surface but a number of deformed platelets with stretched pseudopods and fusing themselves were attached to the positive-charged surface.
These results indicate that electroconductivity is an important factor of anticoagulant effect on blood conduit.

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In the process of wound healing, the development of granulation tissue is necessary, and here the enhancement of insoluble fibrin is essential.
Fibrinogen is converted into fibrin by thrombin and the fibrin cross-links covalently by activation of the fibrin stabilizing factor, factorXIII (FXIII) in the presence of calcium ions to form an insoluble fibrin clot.
We immobilized thrombin and FXIII on gelatin sponge and suture materials which would hopefully enhance the local accumulation of fibrin network.
An absorbable gelatin sponge sheet and some suture materials were immersed into a solution containing thrombin and FXIII, after which they were liophilized.
The immobilized materials were incubated in human plasma or tissue liquid to study local accumulation of the insoluble fibrin both macroscopically and histologically. The materials were also implanted in the rats and observed histologically how much fibrin network were enhanced.
The macroscopical findings of insoluble fibrin clot formation on the immobilized materials was remarkable and the histological findings showed that a large amount of fibrin network had developed homogenously in all parts of the carriers. In the materials implanted in the rats, the formation of fibrin network were so operative_R that they grew in all meshes of the Spongel and the adaptation with subcutaneous tissue was moderate.
The local enhancement of the fibrin network was compatible both in vitro and in vivo and these results strongly indicate that the newly devised materials will be useful for the repair of surgical wound.

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The adsorption of Urokinase (UK) on sulfonated Poly vinylidene Fluoride (PVDF) films was examined. The amount of adsorbed UK on sulfonated PVDF films increased linearly with the degree of the ion exchange capacity (I. E. C) of sulfonate. Moderately sulfonated PVDF film (I. E. C=0.25) adsorbed 3IU/cm² of UK, and highly sulfonated film (I. E. C=0.54) adsorbed 5IU/cm² of UK, respectively.
The addition of the sulfonated films did not result in any change of the viability of rat lymphocytes in vitro. The implant of the film (I. E. C>0.48)into rats resulted in the all infiltration, composed of lymphocytes and plasma cells or the blastogenesis in the surrounding tissues of the implant and regional lymph nodes. On the contrary, the implant of the films (I. E. C.<0.27) did not exert any visible changes, indicating that the lightly sulfonated films may be applicable in the sense of biocompatibility in vivo.

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In this paper the authors report the biochemical studies about healing process of synthetic vascular grafts, i. e. commercially available prosthesis (Dacron and Teflon) and Non-Woven Polypropylene Sheat compounded with Dacron Mesh in the canine subcutaneous tissue, and some grafts in the canine abdominal aorta.
The content of mocopolysaccharides in the collagenous connective tissue surrounding the graft and in the cloth interstices was studied. The histological studies by means of hematoxyline and eosine revealed the almost compleat healing of the subcutaneous implants one year after implantation, but uronic acid and hexosamine were some 7 and 6μmole/g dry wt. respectively, and hialuronic acid content was more than 30% of the total mucopolysaccharides in the same preiod, which means the incomplete healing of the implants.
Furthermore, sustaining of the tissue reaction and incompleteness of the organization were observed in the cloth interstices of the abdominal aorta grafts even two and half years postimplantation. These data suggest that the complete healing of these grafts should require still longer period than generally estimated. The components of mucopolysaccharide in the abdominal aorta implants were quite different from those of the subcutaneous grafts. The amount of chondroitin sulfate was some 40% and of hyaluronic acid negligible in the former whereas chondroitin sulfate and hyaluronic acid was some 15%, 30 to 40% respectively in the latter.The authors believe that these changes were brought about mainly by the arterial pressure and the pseudointima formation.

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Avcothane, Gore-Tex and filler free silicone rubber are known as thromboresistant materials in the case of long-term uses. Cell attachment and cell growth on these three materials were studied kinetically and morphologically by cell culture technique, and compared with those on polyurethane, Teflon and Silastic. The former group of materials exhibited cell response different from the latter; they showed lower degree of initial cell attachment, slower cell growth, and poor elongation of micropseudopods of cells. These specific cell response seems to suggest thromboresistant nature of these materials, and be explainable mostly on the basis of our microheterogeneity hypothesis.

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Removal of antigen, antibody, or immunocomplex is supposed to be meaningful in certain immune diseases in order to at least minimize appearance of the symptoms. Extracorporeal removal of these substances by adsorption is considered to be one of the possibilities for this kind of treatment. Adsorption capability of 22 kinds of materials has been investigated by immurioelectrophoresis and phytoagglunine blast cell adsorption. It is suggested that XAD-7 is the most suitable candidate for this puorpose.

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We previously described that collagen-synthetic polymer composite was adequately applicable as a support of immobilization of enzymes for the purpose of providing the material surface with some biological functions, and that urokinase-bearing composite showed good fibrinolytic activity. We have been also investigating to replace various organs with this composite material experimentally and clinically, for example, reconstruction of trachea, chest wall or esophagus. When such artificial organs are implanted into the body, bacterial infection may cause serious troubles. We have therefore attempted to develop a new method of producing antibacterial biomaterials by immobilization of hen egg-white lysozyme and polypeptide antibiotic Polymyxin B onto this composite material.

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Two patients with idiopathic hypertrophic subaortic stenosis were treated with APICO AORTIC BYPASS GRAFT using valve bearing conduits. Perioperative hemodynamic studies showed left ventricular systolic pressure and left ventricular aortic systolic gradient were mearkedly reduced. This technique seemed to be useful for relief of left ventricular hypertension in idiopathic hypertrophic subaortic stenosis. However, the long term follow-up will be necessary to evaluate the graft durability, complication and left ventricular function in the late postoperative period.

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This report represented the study on nylon immobilized trasylol. The results were as follows:
1. The covalent binding method was performed to link trasylol to the surface of nylon. The amount of immobilized trasylol was increased efficiently by means of providing an intermediate layer of grafted copolymer.
2. The chromotropic acid method which was applied for assaying the activity of kallikrein was found to be usedful for fine determination of immobilized trasylol.
3. The dose of immobilized trasylol to nylon was 0.82±0.06 KIU/cm².
4. The immobilized trasylol had the antitrypsin activity and the antifibrinolytic activity. The procedure of disinfection caused a big loss in the activity.

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A new radiopaque surgical suture has been developed and was used clinically in 43 cases since December in 1977. Any complication has not been experienced with this method.
The operation with the suture shows the following merits:
1)It helps to perform precise and safer post-operatively angiography.
2)It can serve as a guideline for evaluation of operative outcome and anatomicel behavier corrected surgically.
3)It can serve for elucidation of anatomcal relations in cardiac anomalies or dynamic functions of valves after surgicel treatment.
4)The suture can be used in the primary operation to give a better surgical orientation in one second radical repair.

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IABP was employed in 15 patients with severe left ventricular power failure and we discussed indications and limitations of IABP for them.
1) IABP was effective and could he weaned off it for all cases but 4 patients of them were lost. Infarcted area of acute myocardial infarction following cardiogenic shock was extended beyond 50% of left ventricular free wall.
2) Left ventricular dysfunction was indicated IABP before and during operation in 7 cases. (EF<0.50, LVEDP>15mmHg, CI 2.0<1/min/m²) They were obviously improved compared with the cases of which used after operation.
3) Indicatios of IABP will be widespread to unstable angina refractory to medication, septic and others.

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At the National Cardiovascular Center, IA-BP and/or V-A bypass (V-AB) were applied to 54 patients. Forty pts. were weaned off from them and 35 survived longer. Usually moderate heart failure resistant medical treatment, IABP markedly improved general hemodynamics and cardiac function. It is noticed, however, that IABP has the limit of cardiac assistance and duration to be used.
Thereupon more effective use of IABP were considered; (1) Necessity to establish indication and criteria to use IABP for heart failure, (2) Usefulness of prophylactic use of IABP, (3) Effectiveness of combination of IABP with vasodilator or vasopressor.
For the patients over the limit of IABP assistance, at present, combination of IABP and V-AB should be applied actively. In future, when heart assist device had developed, it should be applied widely to profound heart failure.

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Glutaraldehyde preserved xenografts have been recognized as to be hemodynamically superior to mechanical valves, however it was recently uncovered that these xenografts had relatively large pressure gradient.
Fluid dynamic investigation was carried out to make it clear that factors by which these xenografts yield pressure gradient.
As the deflection between valve and flow axis was enlarged over 10 degrees, pressure gradient across the xenograft(Carpentier-Edwards valve) increased. The cusps opened in sequence and the order in which the cusps of a valve open was uniform in a certain position, and in the same direction of valve axis as flow axis the right coronary cusp opened last. As flow increased, number of opened cusps was increased and the pressure gradient ratio was decreased in each cusp opening. If the valve axis was inclined to the opposit side of the right coronary cusp against the flow axis, right coronary cusp was opened earlier and early pressure gradient was decreased.
These fluid dynamic phenomena were not observed in Björk-Shiley valve.

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The effect of artificial organ is compared with the effect of conventional drugs. The former is more powerful and more accurate producing less complications.
The effect of drug is more generalized, and it cannot have selective contribution. For example, the treatment of bradycardia was carried out by administering isoproterenol capusel every 4 hours before the invent of cardiac artificial pacemaker. The effect of isoproterenol was various among patients. But the cardiac pacemaker is very accurate in that patients have the pulse rate of 70 per minute.
Thus, most artificial organs are expected to be superior and mightier than the conventional drugs. In the future, artificial organs including drugs will be clinically employed, which might reduce drugs' side effect markedly.

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