Our clinical data of DVR (double artificial valve replacement) with Björk-Shiley valves had informed that a quarter of the patients died of low cardiac output syndrome, the cause of which were analized from a view point of medical-technology. At first, with the mechanical simulator to cardiovascular system, the characteristics of the single valve of each size as to its response, resistance and leakage flow were made clear. The followings were found; 1) Leakage flow did not show any regularity to the size. 2) Under the same mount of the valvular leakage, response showed positive increment to the size, but resistance negative. Next, hemodynamics of our simulator under the combinations of each two valvular size were compared one after the other. It was found that the optimal ratio of the double valvular sizes (aortic valve diameter vs. mitral one) was 0.7-0.8 at the maximam flow of the pump. These findings were well correlative to those of the clinical DVR data and the anatomical data, respectively.
The experimental replacement of the inferior caval vein extending from thoracic to abdominal with expanded polytetrafluoroethylene tubular grafts of 15 to 20cm in length were performed in fifteen dogs. Of eleven grafts which had an average pore size of one to two microns, there was one occlusion, a 91 percent patency rate. With a follow up period up to nine and a half months, narrowing of its lumen with thickened neointima was not seen in any animal. Of four grafts with an average pore size of two to four microns, two occlusions were observed, a 50 percent patency rate. A thin and well attached neointima was recognized in the inner surface. The neointima consisted of collagen and fibrous tissue and was partially lined by endothelial cells. There was no cellular infiltration into the pores of the grafts.
The effects of intraaortic balloon pumping (IABP) on the severity of myocardial ischemic injury, the collateral flow and the myocardial metabolism were studied in 20 dogs following acute LAD coronary artery occlusion. Following one hour of the observation of the ischemic changes in myocardium, IABP was initiated for one hour using our designed assist device. The significant diastolic augmentation of central aortic pressure and the reduction of left ventricular impedance were observed during IABP. Serial epicardial electrograms revealed that IABP significantly reduced the magnitude and extent of myocardial ischemic injury after experimental LAD occulusion. Retrograde flow from the ischemic LAD bed significantly increased by 42.5±4.30% during IABP (P<0.05). During one hour of IABP, the oxygen extraction rate in the ischemic area was reduced and the lactate extraction rate also significantly improved from-34.8±6.10% to-14.8±4.20% (P<0.05). However, these beneficial effects by IABP were reversed immediately after pump off and therefore to expect the sufficient “after effects” IABP must be continued for longer period until natural development of coronary collaterals is completed. In addition, 4 cases of our clinical trials were presented and the marked improvement in hemodynamics during IABP was observed in cardiogenic shock patient following massive myocardial infarction.
The rapid decrease in hematocrit (Ht) and total protein (Tp), gradual increase in central venous pressure, and peripheral circulatory insufficiency such as impossibility of standing up, poor appetite, anuria or oliguria and constipation or mucous feces were the most serious physiological problems in recent total artificial heart (AH) animal experiments. For these phenomena, a phsiological hypothesis was presented by authors under the consideration of that too much cardiac output for animal might induce such phenomena. As the results of animal experiments with goat, the following finidings were obtained. (1) High cardiac output of AH causes a marked decrease in Ht and Tp, as well as peripheral circulatory insufficiency. (2) By maintaining the cardiac output within the range of 80 to 100ml/Kg/min. during the experiments, maximum and average survival days of the goats replaced totally with AH were markedly prolonged, from 10 days to 54 days and from 4.5 days to 30.5 days, respectively. And the surviving condition of these goats were almost normal physiologically and pathophysiologically. (3) As conclusion, it became obvious that the cardiac output was one of the most important physiological parameter for control of the circulatory system.
The lithium iodine power source is completely dry, producing no gas. The entire system can be hermatically sealed because no outlet for gas is required. However, X-rays of CPI models 401 and 301 show a gas-like formation. There are areas in each cell which are not totally opaque to X-rays. These areas were found in the upper part of the battery when viewed relative to the position of the patient's body. These formations seemed to be due to small void space left in the cell during manufacture or due to iodine vapor. No correlation between these formations and cell functions has been found in our experience.
Alcohol-preserved homologous connective tissue tubes containing polyester mesh within their walls were evaluated as arterial prostheses in the thoracic aortae of 20 dogs. As the control, 146 knitted Dacron prostheses were used. Silicone rubber tubes covered with polyester mesh were implanted in dogs' subcutaneous layers. Two to three weeks after implantation, the tubes and the surrounding connective tissue were removed en bloc as little excess tissue as possible and were dipped and preserved into 70% solution of ethanol. Before the implantation as an arterial substitute, the silicone tube was pulled out and the connective tissue with polyester mesh was immersed into saline solution. Therefore preparation of the grafts of desired size and shape was easily performed. All the dogs were held for sacrifice from 1 to 43 weeks after operation except 4 for long-term observation. All the grafts were patent at the time of removal. The luminal surface was shiny and smooth. Microscopic examination revealed that the fibers of the polyester mesh were enveloped by matured connective tissue. It took 15 weeks after implantation to covered the surface of the neointima completely with endothelium, while in the cases of the control specimens, it took more than 20 weeks. Both gross and microscopic examinations showed no aneurysmal dilatation, nor other degenerative changes such as calcification, ulceration, hyalin degeneration and thrombus deposition. These results indicate that the alcohol-preserved homologous connective tissue tube is superior to the control specimen of the knitted Dacron prosthesis and is acceptable as an arterial substitute.