The clinical results of DVR (double artificial valve replacement) with Björk-Shiley valves for severe combined valvular disease (mean pre-operative EF (ejection-fraction) was 0.36) were unsatisfactory. One of the causes of that matter could be thought that the leakage of Björk-Shiley valves was not so little and this gave an overload to the cardiac muscle especially for the patient with serious diseased heart. However, Björk-Shiley valves had the advantage of the small resistance, on the other hand, Starr-Edwards Ball valves had a little leakage, but large resistance.
Therefore, with the mechanical simulator to the cardiovascular system, hemodynamics under the possible four combinations of the two kinds of valves were compared one after the other. It was found that, among the four, the combination of aortic-Ball and mitral-Björk had the best hemodynamics.
To 4 cases of serious combined valvular diseases (preoperative EF=0.28), this combination of DVR was applied and fortunately every case showed expected results.

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Neo-arterial walls of polyester vascular prostheses were examined under an optical microscope from 30 to 210 weeks after implantation in the thoracic aortae of 50 dogs.
Ulcers of the neo-arterial wall with deposition of thrombi were observed in 50% of all the specimens. In 72% of the specimens with the complication, scar tissue was noticed on the adventitial side of the deseased wall. These observations suggest us that the scar tissue leads to this complication because the neo-arterial wall was forced to be in the poor condition both nutritionally and constractionally due to conversion of the grafts by scar contraction.
From this result, it is hopeful to avoid the complication by making efforts to prevent formation of scar tissue surrounding the grafts during implantation.

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In 9 patients with chronic renal failure, cardiac function was analyzed immediately before and after hemodialysis using the cardiac catheterisation. Long-standing hypertension was seen in all patients but one case.
LA, PA, RV and RA pressure in the predialysis examination was high and each pressure decreased by hemodialysis. In the patients with the pressure of slightly above the normal range, the intracardiac pressure was normalized but no significant improvement was seen in the case who had high intracardiac pressure before hemodialysis.
The ventricular stroke work index was high in both left and right ventricle, however the latter was significantly. The index was normalized by hemodialysis slightly.
After hemdialysis cardiac index decreased in 4 cases, increased in 3 cases and no change was observed in one case. High PSR was decreased however TSR was unchanged by hemodialysis.
Most of these changes were explained by the reduction of circulatory blood volume and the improvement of cardiac reserve although several factors were involved in the pathogenesis of circulatory disturbance.
As the results, it is important to control the hypertension in uremic patients for the prevention of circulatory congestion.

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The effect of venous pulsation on the microcirculation was studied in dogs.
An apparatus producing pulsatile venous flow was utilized on one side in regional perfusion of both hind legs for 4 hours. The venous flow rate did not decrease in cases with pulse pressure of 1, 5cm. H₂O, 2, 5cm. H₂O and 3, 5cm. H₂O. The oxygen saturation of venous blood was generally lowes on the pulsation side than on the nonpulsation side. The oxygen consumption was higher on the pulsation side than on the nonpulsation side.
The intramuscular PO₂ was also higher on the pulsation side.
On histological examination, muscle perfused with palsatile venous flow of 1, 5cm. H₂O and 2, 5cm. H₂O pulse pressure showed no abnormal findings. In cases of 3, 5cm. H₂O pulse pressure, diffuse hemorrhage and interstitial edema were recognized. These findings suggestd that venous pulsation with a proper pulse pressure might be effective to maintain the microcirculation.

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Many experimental and clinical studies have been done to develop more optimal vascular prostheses. Newadays many vascular grafts are available in clinical use, but these grafts are not so optimally organized in man as in experimental animals. Then we should select the more ideal prostheses to expect long-term patency. In order to estimate the most optimal grafts, we make a new graft combining two different grafts longitudinally and evaluate the organization experimentally. This method is most simple and objective to select the most valuable graft.

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Determination of DEHP eluted from PVC blood tube for a commercial artificial kidney into plasma solution was carried out using gas-chromatography.
Three hundred ml of plasma solution was circulated continuously in the tube for 24 hours at a speed of 240ml/min, and about 18mg of DEHP was found after 6 hours since circulation started in the solution.
There was no evidence that the amount of DEHP eluted from the tube was harmful, considering together with its toxicity, metabolism and the other biological studies.
However, regardless of the toxicity, it is not desirable that foreign material enter the body. So efforts to minimize eluted material as little amount as possible have been made.
Amount of DEHP eluted decreased to about two-third using silicone tube instead of PVC tube of blood pump. Furthermore, it decreased to about one-tenth when the whole blood tube except the section of blood pump was replaced to PVC tube which did not contain DEHP.
As a result of this study, it was found that the amount of eluted from PVC blood tube was due to inner surface area of the tube rather than squeezing action of the blood pump.

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