A J Snyder

The LionHeart LVD-2000 : a completely implanted left ventricular assist device for chronic circulatory support

Management of patients with end-stage cardiac disease remains a vexing problem. Limitations in medical management and a fixed supply of donor organs for cardiac transplant have a continued impact on this growing population of patients. Mechanical circulatory support has proved very successful as a means of bridging patients to cardiac transplant when all medical options have been exhausted. The development of a chronic system of circulatory support has been underway at the Pennsylvania State University for nearly 30 years. These efforts have been recently merged with the industrial partnership with Arrow International toward the development of the LionHeart LVD-2000 (Arrow International, Reading, PA) completely implanted left ventricular support system. We present an overview of the system, details of implantation, a review of preclinical studies, and a synopsis of the first European implants. Early results have demonstrated the system to be safe, effective, and reliable. Transcutaneous energy transmission and the compliance chamber have been validated.

An investigation of the in vivo stability of poly(ether urethaneurea) blood sacs

In this paper we investigate the biostability of a series of Biolon blood sacs that were utilized in electric total artificial hearts for time periods of up to 19 weeks. A battery of experimental probes, including scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), were used to characterize the bulk and surface properties of explanted and control blood sacs. Gel permeation chromatography (GPC) experiments showed that generally there was a dramatic increase in average molecular weight at longer implantation times. However, SEM and GPC observations suggest significant deterioration of the flex regions of right blood sacs after 17 weeks of service. XPS experiments indicated appreciable silicon and hydrocarbon concentrations on blood-contacting surfaces both before and after implantation, and we speculate as to their origin.

The Penn State implantable artificial heart: Current status

For treatment of patients with intractable biventricular failure for whom heart transplantation is not appropriate, we are developing an implantable artificial heart system. The artificial heart is composed of an electromechanical driver that alternately compresses the blood sacs of pumps mounted to both sides. We have demonstrated one-year operation in vitro without failure or signs of wear. The hermetically sealed device has been implanted with percutaneous wires in eight experimental animals and has performed well.

Recent Improvements In The 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.

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.

Completely Implantable Total Artificial Heart and Heart Assist Systems: Initial In Vivo Testing

We have developed and tested systems for long-term heart replacement ventricular assistance without percutaneous leads. A rollerscrew energy converter actuates a single sac-type blood pump for ventricular assistance, or alternately ejects the left and right pumps of a total artificial heart. A simple compliance chamber assures modest variation of pressure within the sealed energy converter housing. An implanted canister contains control electronics and a battery capable of providing 30–50 min of operation. Energy is transmitted inductively from a ring-shaped external coil to a mound-shaped subcutaneous coil. Information is transmitted to the implant by frequency modulation of the power carrier and from the implant by radio frequency transmission. External equipment includes a battery pack with simple indicators, a battery charger, and a physician’s office or laboratory monitoring system. Both systems have undergone initial in vivo testing in calves. Eleven total artificial heart recipients survived from 1 to 118 days. The most common complication of the implant procedure was pulmonary dysfunction. The longest-surviving recipient was euthanized for progressing sepsis originating at a percutaneous monitoring line. The first assist system operated for 84 days before failure of the energy transmission secondary coil. The second assist implant is ongoing at 125 days. These studies thus far have demonstrated the implantability of the systems and have verified the proper function of the implanted controller. Experiments will continue in order to determine long-term interactions with the recipient.