Wilson Greatbatch

The Solid-State Lithium Battery: A New Improved Chemical Power Source for Implantable Cardiac Pacemakers

A new solid-state battery, designed for implantable prosthetics is described. Single cell voltage is 2.8 V. The anode is metallic lithium. The cathode is a proprietary iodide. The electrolyte is a crystal, lithium iodide. Cell impedance at 37°C for a typical pacemaker battery is under 1000? at beginning of life (BOL) and 16 000 ? at end of life (EOL). The simple chemistry of the cell precludes hydrogen gas generation and thus, for the first time, permits hermetic sealing of a battery and/or pacemaker in a welded stainless-steel enclosure which may be used as the indifferent anode electrode in a monopolar system.

POLARIZATION PHENOMENA RELATING TO PHYSIOLOGICAL ELECTRODES

Electrochemical polarization of physiological electrodes is an undesirable but seemingly unavoidable phenomenon that detracts from the performance of implanted electronic prosthetic devices. In the case of noble metals, polarization causes a significant waste of stimulation energy at the electrode surface. With non-noble metals, the energy waste is even greater and may involve electrolytic corrosion reactions. Such corrosion may destroy the electrode and may possibly leave toxic residues in body tissues. The electrode-electrolyte interface presents to a cardiac pacemaker a highly capacitive load having multiple time constants of the same order of magnitude as the 1or 2-millisecond (msec) duration of a pacemaking impulse. Thus, an applied square wave of current on the electrodes does not obey Ohm’s law and does not elicit a square wave of voltage, nor is the voltage waveform a constant slope (ramp), as would be expected from a single lumped capacitor. Rather, the voltage rises in less than a microsecond to an initial value and then more slowly, in at least two different time constants, until the end of the pulse. Polarization of physiological electrodes was noted many years ago by Cole ( 1934) and later by Schwan and co-workers (1954). Previous publications have reported electrode data to confirm the surface aspect of this phenomenon (Schneider, 1964; Greatbatch, 1966; Mansfield, 1967). It has also been shown that the phenomenon is strongly dependent on the specific electrode material as well as on current density (Weinman & Mahler, 1964; Briller ef al., 1966; Greatbatch, 1966, 1967c), leading to the inescapable conclusion that the phenomenon must be electrochemical polarization of the electrode surface. The fundamental electrochemistry of electrode processes is very complex and beyond the scope of this presentation, but some experimental observations and considerations can be cited relating to important properties of physiological electrodes. When a voltage is applied to a pair of electrodes in a saline bath, charged ions in the fluid drift along the resulting potential gradient, chloride ions toward the anode and sodium ions toward the cathode. If the electrodes are nonpolarizable types such as silver coated with silver chloride, the accumulating ions will discharge at the electrodes, and current will flow into the external circuit, even at small applied voltages. The electrode-electrolyte system will then present a relatively linear resistive load to the voltage source and will approximately obey Ohm’s law if the current density is not too high. If, however, the electrodes are polarizable, and this includes all purely metallic conductors, ions and monatoms will accumulate within a micron of the surface of the metal, but very little steady-state current will flow across the electrode-electrolyte interface until a

LITHIUM/CARBON MONOFLUORIDE (LI/CFX) : A NEW PACEMAKER BATTERY

The reduction in pacemaker size coupled with the addition of more current demanding functions has motivated the development of batteries that can supply higher current densities at useful voltages than the lithium/iodine batteries in use today while retaining the volumetric energy density of that system. The lithium/CFx system offers an attractive alternative for advanced pacemaker systems. The battery can deliver currents in the milliampere range without significant voltage drop. The system is compatible with titanium casing, allowing a 50% reduction in weight over the same size lithium/iodine battery. Cells have been designed and tested in these laboratories and have been shown to be suitable for advanced pacemaker applications.

The Lithium/Iodine Battery: A Historical Perspective

The lithium/iodine‐polyvinylpyridine battery, first implanted 20 years ago, has become the power source of choice for the cardiac pacemaker. Over the last 20 years, improvements in cell chemistry, cell design, and modeling of cell performance have been made. Cells today exhibit an energy density over three times as great as cells produced in 1972. Well over 2 million pacemakers have been implanted with this chemistry, and the system has exhibited excellent reliability.

A Pu 238 O 2 Nuclear Power Source for Implantable Cardiac Pacemakers

Implantable cardiac pacemakers are currently powered by mercury batteries. These cells have approximately 50-percent reliability for 2-year operation in this application. The patient has an expected lifetime of five and one-half years. Thus the cardiac pacemaker must be replaced several times during the patients lifetime.

A Microcalorimeter for Nondestructive Analysis of Pacemakers and Pacemaker Batteries

A microcalorimeter has been built by the authors and used to measure internal losses in primary pacemaker batteries. Power dissipation of 10-50 ¿W has been measured in new pacemaker batteries, much of which is traceable to innocuous exotherm from continuing curing of plastic materials in the battery. True internal shorts have produced 1000-2000 ¿W of heat. Present noise level is about 3 ¿W. A noise level of under 1 ¿W should be achievable. Such a microcalorimeter should prove invaluable for nondestructive early identification of parasitic power losses, both in batteries and in completed pacemakers.

Blood transfusion and AIDS in the USA.

WE have examined data for 3518 cases of transfusion-acquired AIDS (TA-AIDS) onsets as reported to the USA Centers for Disease Control (CDC) through 30 June 1990. We discarded 1077 of these records because of missing or uncertain date of infection. We present here infection and onset data on the remaining 2441 cases in a Rees Plot of year of onset vs. year of infection. This is probably the only class of AIDS patients for whom the date of infection is reasonably ascertainable. Also the large number of cases which we present, by cohorts of year of infection, should be useful for epidemiology and for public health planning purposes.