TOTALLY IMPLANTABLE INTRATHORACIC VENTRICULAR ASSIST DEVICE

Background. A totally implantable, intrathoracic electrohydraulic vent ricular assist device (EVAD) is being developed for permanent use or a s a bridge to transplantation. Methods. The blood pump with 70-mL nomi nal stroke volume, volume displacement chamber, reversible turbine, in ternal electronics and infrared diaphragm position sensor are combined in one compact unit (unified system). The size and geometry are based on human anatomic measurements and fluid dynamic studies. A transcuta neous energy transfer powers the system and recharges the implantable nickel-cadmium battery pack. Autotuning circuitry optimizes energy tra nsfer efficiency over a range of transcutaneous energy transfer coil s pacings and misalignments. An infrared diaphragm position sensor detec ts end-systole and diastole points. Results. In vitro and acute in viv o tests have demonstrated flow rates greater than 6 L/min. The transcu taneous energy transfer system demonstrated power transfer efficiencie s of 60% to 80% for power demands from 5 to 60 W. Thirteen systems are currently undergoing durability testing; one has run for more than 75 0 days failure-free. The system recently sustained circulation in an a cute calf implantation for 96 hours. Conclusions. Results of the in vi tro and in vivo testing to date have demonstrated that the developed s ystem can function effectively as a totally implantable ventricular as sist device. Chronic in vivo evaluation is planned.