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In totally implantable ventricular assist device systems, measuring flow rate of the pump is necessary to ensure proper operation of the pump in response to the recipient's condition or pump malfunction. To avoid problems associated with the use of flow probes, several methods for estimating flow rate of a rotary blood pump used as a ventricular assist device have been studied. In the present study, we have performed a chronic animal experiment with two NEDO PI gyro pumps as the biventricular assist device for 63 days to evaluate our estimation method by comparing the estimated flow rate with the measured one every 2 days. Up to 15 days after identification of the parameters, our estimations were accurate. Errors increased during postoperation days 20 to 30. Meanwhile, their correlation coefficient r was higher than 0.9 in all the acquired data, and estimated flow rate could simulate the profile of the measured one.

The left atrium and the left ventricular apex are the most commonly used sites of inflow cannulation for postcardiotomy left ventricular support. A new cannulation technique that requires only an ascending aortotomy is introduced. This procedure can be undertaken with equipment present in any cardiac operating room and may prove to cause fewer complications than conventional cannulation techniques.

To determine anatomic parameters for a permanent, electrically actuated left ventricular assist device (LVAD), the effects of abdominal placement of pneumatic LVADs used as temporary support for patients awaiting heart transplantation was studied. Understanding the anatomic constraints imposed by the abdominal viscera in LVAD placement is crucial, because improper placement can result in compression or obstruction of adjacent structures. Anatomic compatibility was assessed in four men (age 22-48 years) who were supported by the LVAD for over 1 month (range 35-132 days). The pump was intraperitoneally placed in the left upper quadrant. Radiographic techniques were employed, including CT scanning (with patients supine) and contrast imaging (patients in anatomical position), and the pump and conduits appeared to be properly positioned, with minimal compression of the body of the stomach, and no obstruction of adjacent organs. Three patients returned to a solid food diet and exercised daily by stationary cycling and walking. No signs of migration or erosion of the pump were present at the time of LVAD removal and cardiac transplantation. Successful clinical experience with short-term use of the LVAD suggests that the electrically actuated device can be well tolerated in patients requiring permanent left ventricular assistance.