TOWARD COMMERCIALIZATION OF TOTALLY IMPLANTABLE, ULTRACOMPACT TOTAL ARTIFICIAL HEART AND VENTRICULAR ASSIST SYSTEMS

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In this project, ultracompact, totally implantable total artificial heart (TAH) and ventricular assist system, pulsatile and nonpulsatile, have been developed and their performances were evaluated in vitro and in vivo using calves. The TAH is a one-piece design sandwiching a compact electromechanical actuator between the left and right pusher-plate type blood pumps. The stroke length and stroke volume of the blood pump are 12mm and 55cc. The VAD was designed using the same components as those of TAH by covering the TAH's right side with a back-plate. The dimensions of the TAH are 90mm diameter, 70mm thickness, 400cc volume and 450g weight, while those of the VAD are 90mm, 56mm, 275cc and 460g. The VAD and TAH are much smaller than the currently clinically available systems. (As for performance of the devices, both TAH and VAD generated the maximum flow of 8L/min. The power requirement for VAD ranged from 5 to 8 watts to generate the flow of 4 to 8 L/min against the pump afterload 100mm … More Hg. On the other hand, the TAH required approximately 10 to 15 watts to generate the flowof 4 to 8 L/min against the left and right afterload of 100 and 25mmHg, respectively. The maximum electrical to hydraulic conversion efficiency was 23% for VAD, while for TAH 13.5%. As the associated components for totally implantable system, compliance chamber and rechargeable batteries were also designed and assembled. The displaced volume of the compliance chamber for VAD is 75cc, while for TAH 55cc. The flexing diaphragm of the compliance chamber was made of polyurethane through dip-coating technique.The anatomical fitting and survival studies with VAD and TAH were performed in one calf for VAD and a total of 6 calves for TAH. As for VAD, the blood was drained from the left ventricular apex and returned to the descending aorta through the VAD. The compliance chamber was implanted in the thoracic cavity and drive line was tunneled underneath the skin to outside the body and connected to the driver. Because of the ventricular fibrillation developed during the surgery, the animal could survive only 24 hours. However, entire implantation procedure has been worked out successfully. Concerning TAH, in the first two calves anatomical fitting study was carried out, followed with TAH implantation in the remaining 4 calves. The heart-lung bypass was performed to excise the native heart, followed with implantation of the TAH. In the last calf # 0107, all the procedure successfully worked out to obtain 30 hour survival with the TAH. The animal was extubated and stood up on his own. The animal was sacrificed 30 hour postoperatively due to reduced left pump flow. Left-right flow balance procedure needs to be improved to better control left and right atrial pressure together with left pump flow. We will continue with in vivo evaluation of the TAH, focusing on durability and biocompatibility aspects, to develop clinically usable totally implantable TAH system.In addition to pulsatile systems, we also designed and evaluated a single pivot bearing supported centrifugal blood pump. Pump performance, hemolysis test as well as two month durability studies were carried out to evaluate its feasibility as a left ventricular assist device. We will move onto animal study in the next phase.In order to monitor the patients implanted with artificial heart systems, a reflectance type optical sensor was developed to monitor hemoglobin content and oxygen saturation of the blood inside the artificial heart. Although excellent results have been shown in vitro, animal evaluation must be conducted to evaluate its long term performance in vivo. Less