Jinko Zoki

In order to realize control tasks of the artificial heart or monitoring of physiological state of the patient supported by the artificial heart, it is very important to measure parameters of cardiovascular dynamics such as cardiac output and blood pressure. However, we should avoid direct measurement of cardiac output or blood pressure by means of sensors positioned in the body, which may cause many problems such as biocompatibility, durability, drift, and so on. The present study tried to estimate, without direct measurement, cardiac output or blood pressure which may be used in controlling a total artificial heart (a motor driven centrifugal pump) by means of a neural network (NN) or a linear time series model (ARMA model) on the basis of the data obtained from a mock circulatory system. It was revealed that NN maybe superior to ARMA model from the view point of versatility which will be important in the application stage of the total artificial heart.

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We have studied the influence of graft incorporation on the morphology of anastomotic false aneurysm. From 1980 to 1994, 20 patients developed a total of 25 anastomotic false aneurysms; 12 in the aorta and 13 in the femoral artery, These aneurysms occurred an average of 9.1±7.7 (SD) years after the original vascular procedures which included 8 aortoiliac occlusive disease, 7 abdominal aortic aneurysm, and 5 Takayasu arteritis. We have implanted 2 knitted Teflon, 4 woven Teflon, 3 non-velour woven Dacron, 3 non-velour knitted Dacron, and 10 double velour knitted Dacron grafts in the initial operations. Anastomotic false aneurysms developed with woven graft, which showed poor incorporation; all extended along the graft dividing the weak adhesion between the graft and surrounding tissues. In one case, this expansion seemed to influence rapid worsening of the clinical course. Anastomotic false aneurysms also developed with double velour knitted Dacron grafts in spite of their good incorporation. In all but one unidentified case, they were confined to disrupted area of femoral anastomoses. Tight adhesion of the graft to surrounding tissues could prevent aneurysmal progression in these cases. In conclusion, a graft of good incorporation seems to prevent rapid extension of an anastomotic false aneurysm and abrupt deterioration of the clinical course.

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MENOX AL 6000 is a new extracapillary blood flow type Polyolefin (PO) hollow fiber membrane oxygenator. We clinically evaluated MENOX AL 6000 comparing it with CAPIOX SX (Terumo). Thirteen patients who underwent elective coronary artery bypass grafting were divided into two groups, MENOX AL 6000 group (group M: 7 patients) and CAPIOX SX group (group C: 6 patients). In this study, blood samples were collected 5min before and after the initiation of cardiopulmonary bypass (CPB), then every 30min during CPB. The gas transfer capability was satisfactory, when it used MENOX AL 6000 for the patients with weights of 42.8-72kg. Corrected platelet count and plasma free hemoglobin were measured, and there were no significant differences between the two groups. However, the hemolysis index (plasma free hemoglobin/CPB time) was lower in group M than that in group C. Futhermore, as a result of a simple experiment (in vitro) which was originally devised to investigate the biocompatibility of PO hollow fiber in comparison with that of POlypropylene (PP) hollow fiber, the influence of PO hollow fiber on human blood (platelet count, TAT, FPB, C3a) was less than that of PP hollow fiber. In conclusion the membrane structure of the new oxygenator (MENOX AL 6000: made of PO hollow fiber) had a superior effect on human blood in comparison to that of the CAPIOX SX (made of PP hollow fiber).

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MENOX AL-6000®, which was newly developed for solving serum leakage problems in long term use and activation of platelets, was clinically evaluated in 20 cases, in comparison with other membrane oxygenators, CAPIoxsx® (10 cases) and UNIVOX® (12 cases). MENOX AL-6000®, made of two-layer hollow fiber, showed slightly low oxygen transfer and required significantly more V/Q for CO₂ removal than CAPIOX SX®, but there were no problems in clinical use. The decreases of platelet counts and plasma free Hb during extracorporeal circulation were very slow, and no significant differences were recognised among the three oxygenators. The function of gas exchange in MENOX AL-6000® was not disturbed as time went on. From its structural characteristics, MENOX AL-6000® appears useful for open heart surgery and promises to be effective for longer assist bypass with good result.

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