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Total Artificial Heart (TAH) development at Penn State University and 3M Health Care has progressed from design improvements and manufacturing documentation to in vitro and in vivo testing to characterize the system's hemodynamic response and energetic performance. The TAH system is completely implantable and intended for use as an alternative to transplantation. It includes a dual pusher plate pump and rollerscrew actuator, welded electronics and battery assembly, transcutaneous energy transmission system, telemetry, and a compliance chamber. In vitro testing was conducted on a Penn State mock circulatory loop with glycerol/water solution at body temperature. Tests were performed to characterize the preload and afterload response, left atrial pressure control, and power consumption. A sensitive preload response was demonstrated with left atrial pressure safely maintained at less than 15 mm Hg for flow rates up to 7.5 L/min. Variations in aortic pressure and pulmonary vascular resistance were found to have minimal effects on the preload sensitivity and left atrial pressure control. In vivo testing of the completely implanted system in its final configuration was carried out in two acute studies using implanted temperature sensors mounted on the electronics, motor, and energy transmission coil in contact with adjacent tissue. The mean temperature at the device-tissue interface was less than 4 degrees C above core temperature.

The total artificial heart under development by the Pennsylvania State University and 3M Health Care has undergone a number of design improvements to improve reliability, manufacturability, implantability, and performance. These improvements are nearing completion in preparation for formal durability testing. The redesigned implanted electronics canister, consisting of a welded titanium shell with hermetic connectors, contains the control, telemetry, and energy transmission electronics, as well as a 9 cell, 800 mAhr Ni-Cd battery pack. Functional changes include a reduction in the battery recharge time from 14 hours to 4 hours, and a new inductive telemetry system. The energy transmission system operating frequency has been increased from 160 kHz to 200 kHz. Electromagnetic interference filters and a more efficient control mode have also been implemented. The energy converter has been modified to incorporate a new motor with integral Hall effect position sensors, and new cable, and compliance chamber conduit fittings. High flex life cable is now used for the motor and coil cables. Two prototype durability mock circulatory loops have been built and are being tested. Substantial progress has been made in the completion of manufacturing documentation, and in the implementation of a quality system.

The authors performed 14 implants of a completely implanted total artificial heart (TAH) system in calves. The system consisted of a dual pusher plate rollerscrew energy converter, two sac type blood pumps, an implanted electronic control and battery package, and a transcutaneous energy transmission system. Ten of the implants included a percutaneous lead for monitoring of the implant; the remainder made use of wireless two way telemetry between the implant and the outside. Three animals survived the perioperative period. These calves survived for 98 to 118 days, and one was still alive at 150 days. Causes for termination of the 98 and 118 day cases were abdominal pocket sepsis originating at a monitoring line, and systemic sepsis acquired perioperatively. Death or termination in the shorter cases was mainly due to respiratory complications or bleeding. The TAH system proved capable of providing adequate cardiac outputs at modest atrial pressures. Wireless monitoring and wireless intervention for weaning from cardiopulmonary bypass were readily achieved. All organ systems functioned normally in the presence of the device. Once recovery from implantation in these very young animals was achieved, the system proved its ability to reliably support these animals until body mass exceeded its cardiac output capabilities.

Little information is available regarding the current patterns of medication use in long-term dialysis centers. Therefore, we surveyed the medication records of 1,023 patients undergoing long-term dialysis therapy in 27 dialysis centers. The mean number of medications prescribed per patient was 7.7 +/- 0.54, increasing patient age, increasing duration of dialysis, in-center dialysis, and the presence of underlying diabetic and hypertensive nephropathy were associated with increased frequency of medication use. The use of multiple pharmacologic agents was associated with a high frequency of drug duplication (12%), potential dosage error (9%), potential significant drug interaction (15%), and use of contraindicated drugs (2.5%). A lack of individualization of the use of several pharmacologic agents was apparent. An extreme degree of center variability in drug use was also apparent. Periodic review of medication use should be undertaken in the long-term dialysis setting.

Obesity in migratory birds appears to differ from obesity in man in that gains and losses in body weight do not involve changes in the tissue structure of the body; fat is added to and used from preexisting tissue spaces without appreciable change in the water content or the nonfat dry weight of the body as a whole. Evidence is presented which supports the hypothesis that the nonfat body is essentially homeostatic during migration despite very large scale changes in total body weight.