A ventricular assist device system developed at National Cardiovascular Center, produced by TOYOBO, was clinically evaluated at four different institutes. The system consists of an air-driven, diaphragmtype pump made of segmented polyether polyurethane and a control-drive unit with an automatic level control system of atrial pressure and blood flow. Ten patients, eight adults and two children, with profound heart failure were treated with this system for 45min-12days. Seven of them were applied with a left VAD and three with right VAD. Four cases recovered to be weaned from the system and three patients were long-term survivors. The pump showed excellent anti-thrombogenicity and durability. The control-drive unit functioned correctly without any troubles including the automatic level control system. In conclusion, this VAD system is effective and reliable to treat clinical profound-heart-failure cases. We believe that many patients with profound heart failure will be saved by a well-established therapeutic system with VAD.

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In the open heart surgery for neonates and infants, the precise regulation and control system of extracorporeal circulation is essential. For this purpose, the very compact circuit was designed and applied experimentally and clinically. It consists of two portions, main circuit and additional parts. Main circuit is closed and non-reservoir system. Its priming volume is under 400ml, including 50ml flexible bag. The flexible bag functions as a safety guard. When the bag collapsed completely, the negative pressure occurs in the venous line but it does not transmit to the patient's heart across the bag. Under this system, if necessary, any excess or lack of circulating blood is regulated temporarily by opening the connecting line to the reservoir of additional system in a short minutes. Three hours hypothermic extracorporeal circulation including one hour aorta cross clump using small canine (B. W. 6-7kg) and the clinical application for infant cases (VSD and ECD) were performed without any problem. No unacceptable hematologic data were obtained in this series. Using this system, however, surgeons should take care much more than before to suction the blood separately from other crystalloid solution during procedure. It is essential and the most important point to use this system in success and to perform the extracorporeal circulation safely in neonates and infants.

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In our ventricular assist device system, the bypass flow is measured by an electromagnetic flowmeter, the probe of which is hooked on the woven Dacron® graft of the outlet conduit. To clarify the reliability of measured value, an in vitro test was performed. When a straight tube was used, measured flow by a cuff-type probe was 30% more than the true value which was directly obtained by measuring the overflow volume. Magnetic field across the probe (Nihon-koden FR-type), which we currently use, is not uniformed because of the rectangular situation of positive and negative electrodes. Therefore, a direction of stream line across the probe has a great influence on measured flow. Since we always use a curved outlet conduit, we must take the influence mentioned above into consideration. In our case, the measured flow was 7 to 16% less than the value obtained with a straight tube. In conclusion, the measured flow in our experimental and clinical cases would be 10 to 22% more than the true value. This error might be permissible for clinical usage.

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