Modifications in surgical implantation of the Penn State electric total artificial heart.

BACKGROUND: Two modifications of the surgical implantation protocol for the Penn State Total Artificial Heart (ETAH) were evaluated: Phrenic nerve ischemia was prevented by minimizing dissection and traction; and hemostasis was augmented and ETAH cuff anastomoses reinforced by using fibrin glue. METHODS: Thirteen Holstein calves underwent orthotopic surgical implantation of the Penn State ETAH between February 1998 and August 2000. Mean hemodynamic and laboratory chemistry variables from the first postoperative week were compared between calves receiving the original (n = 7) and modified (n = 6) protocol. RESULTS: Calves assigned to the modified protocol displayed an improvement in the Po2/FiO2 ratio compared to original (419.4 +/- 17.5 vs 336.3 +/- 35.4, respectively; p = 0.05). All additional parameters were equivalent between groups. The percent survival of animals receiving the modified protocol at 2, 4, and 12 weeks was higher than that of animals that underwent the original protocol. Original-protocol calf deaths consisting of hemothorax (n = 3), and respiratory failure (n = 1) were prevented in the modified protocol. CONCLUSIONS: Our results suggest that manipulations in surgical protocol may promote increased survival in calves implanted with the Penn State ETAH.

Postoperative pulmonary complications in calves after implantation of an electric total artificial heart.

In long-term studies testing the Penn State Total Artificial Heart involving 30 calves, seven calves died of pulmonary complications within 2 weeks after receiving the implant (Group 1 [G1]) and seven calves survived from 2 weeks to 3 months without infection (Group 2 [G2]). Comparative studies were performed using multiple variables: cardiopulmonary bypass (CPB) time, cardiac index, central venous pressure, leukocyte count, hematocrit, total protein, albumin, serum glutamic oxaloacetic transaminase (GOT), creatinine, water balance, and transfused blood volume. In G1, CPB time was longer than in G2 (182 +/- 19 vs 156 +/- 17 minutes, respectively, p = 0.018). Postoperative minimum total protein and albumin in G1 were lower than those in G2 (56.5% +/- 6.0% and 59.0% +/- 5.5% of preoperative values vs 68.4% +/- 8.5% and 67.8% +/- 6.1%, respectively, p = 0.011 and 0.015). Water balance in G2 was more positive than in G1 (11.7 +/- 6.8 vs 1.4 +/- 8.3 L, respectively, p = 0.020). Other variables showed no significant differences. Microscopic findings of the lung in G1 were congestion, hemorrhage, aggregation of neutrophils, and proteinaceous material within the interstitial tissues and alveoli.

Recent improvements in a completely implanted total artificial heart.

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.

Steady state hemodynamic and energetic characterization of the Penn State/3M Health Care Total Artificial Heart.

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.

Dynamic in vitro and in vivo performance of a permanent total artificial heart.

In vivo characterization studies were performed to compare the dynamic in vivo performance of the Penn State/3M Health Care electric total artificial heart to existing in vitro data. Fully implanted systems were utilized including the artificial heart, controller, backup batteries, compliance chamber, and transcutaneous energy transmission. Catheters were implanted to measure central venous pressure (CVP), left atrial pressure (LAP), right atrial pressure (RAP), pulmonary artery pressure (PAP), and aortic pressure (AoP). Cardiac output (CO) was determined from the implanted controller, and systemic vascular resistance (SVR) was calculated. Steady state data were collected for each animal along with data regarding the transient responses to changes in preload and afterload. Preload was manipulated through volume changes. Afterload changes were accomplished through vasoactive agents. Increased preload caused little change in cardiac output because the pump output was nearly maximum at baseline. LAP, AoP, and SVR increased with increasing RAP. Decreased preload caused a reduction in CO, LAP, and SVR. Afterload increase resulted in a slight decrease in flow and an increase in system power and SVR. Afterload reduction was accompanied by a decrease in preload and a concomitant reduction in flow. Overall, the system response was similar to the response observed in vitro.