Abstract: There is provided a programmable pacer which is adapted to be programmed from an external source in either a slow program mode, wherein the external source is a simple magnet, or a fast program mode wherein the external programming signals are generated automatically and comprise a constant magnetic signal along with a modulated relatively high frequency magnetic signal. The pacer has means for receiving both fast and slow type program signals and means for processing the received program signals, whether of the fast or slow type, to derive control signals therefrom when the program signals conform to a predetermined program arrangement.

Abstract: A monolithic pacer is provided which utilizes I.sup.2 L circuitry in combination with linear transistors, providing the conventional advantages of analog circuitry together with the flexibility of digital circuitry. Low current drain operation is achieved by current source control of circuit operating conditions, with I.sup.2 L gates being utilized alone and in combination with linear transistors to provide current sources. The pacer provides "on-demand" logic and is externally programmable.

Abstract: A circuit is disclosed for providing automatic detection of end of life of a battery source, particularly a lithium iodine type battery source characterized by a sharply increased internal resistance characteristic near end of life. The circuit periodically samples the short circuit output current of the source, the sampling being done at a high switching speed and for an extremely short time duration so that power consumption is minimized and only the resistive component which causes the knee in the resistance characteristic is measured. In the embodiment as incorporated in a cardiac pacer device, detection of the internal resistance knee is utilized to cause a step change in an operating characteristic of the pacer, such as stimulus rate, whereby end of life can be accurately monitored.

Abstract: An epicardial lead is disclosed having plural electrode tips adapted for securing to the epicardium while moving the electrode at a small angle with respect to the external surface of the heart. At least 2 electrode tips are provided which are curved downward from the bottom surface of the electrode head and backward toward the proximal end of the electrode, so that they can be hooked into the epicardium while pulling the entire lead in a generally backward direction along the surface of the heart. Anchor means are provided at the forward or distal tip of the electrode head, with means for projecting the anchor out of the bottom surface and forward so as to anchor the electrode head against forward movement thereof. The result is a lead which can be firmly secured to the epicardium by two quick movements while maintaining the lead in close proximity to the heart surface, such that minimum access to the heart surface is required.

Abstract: An atrial lead assembly is provided which is adapted for curving into position within the atrium, the lead having a flexible length without any preset curve, and comprising stylet means for introducing a curve into the distal end of the lead. The stylet enables the operator to set the axis of the lead along a curvilinear path adjustable by the operator. The lead has a tip of a continuous helical type adapted to be rotated into contact with the trabeculae, the lead being rotatable about the stylet while the stylet maintains the lead axis in a desired position, whereby the tip is caused to engage the trabeculae. After such engagement, the stylet can be removed, leaving the lead tip in good fixation with the atrial wall.

Abstract: An implantable programmable pacer is disclosed which incorporates a program logic system for receiving magnetic signals from a simple magnet source applied external to the patient, and for translating the simple magnetic signals into logic signals for re-programming selected pacer parameters. The circuitry of the programming system is adapted to react to predetermined timed sequences of application of the external magnetic signal, which timed sequences are correlated with successive intervals of the pacer stimulus generator. The programming system is adapted to interpret predetermined patterns of external application of a magnetic field as instructions for re-programming respective operating parameters.

Abstract: A cardiac pacer for providing stimulus signals for pacing a human heart, adapted to utilize a lithium-type battery source having an internal resistance which increases with the energy depletion of such source, and having an interface circuit adapted to transfer power from the lithium-type battery source to the circuitry for providing stimulus signals, which interface circuit provides transfer characteristics which are a programmed function of said lithium source internal resistance.

Abstract: A low current drain amplifier system, adaptable for use in cardiac pacers and other applications requiring low current drain operation, having an amplifier path comprising transconductance amplifier means characterized by having the circuit characteristic of a current source at its output, the transconductance amplifier means direct driving an active circuit having a high impedance input, and a current source supply for maintaining fixed current operation of the amplifier system elements. In the preferred embodiment, the amplifier path contains a first OTA operating as an amplifier of received signals, the first OTA having its output direct coupled to an input of a second OTA which operates as a comparator, the output of the comparator OTA being direct connected to an IC transistor element.

Abstract: A demand pacer, such as a cardiac pacer for delivering cardiac stimulus pulses on demand, having an oscillator producing an output which is normally gated for delivery, a low current drain amplifier which is substantially insensitive to voltage source variations for amplifying received natural signals, and logic circuitry for performing a plurality of functions including resetting the oscillator following each received natural signal. In the absence of interference, reset of the oscillator is blocked for a refractory period following either a delivered stimulus pulse or a detected natural signal, and means are provided for inhibiting delivery of a stimulus signal at time of oscillator reset. Current source configurations are utilized for supplying power to the amplifier and logic portions, and the amplifiers are also interfaced into a current driver, which techniques contribute to extremely low power consumption and insensitivity to power supply variations.

Abstract: A pacer having a DC to DC converter for use with a relatively low voltage power source, and for providing a raised voltage supply to a load characterized by having a first circuit portion which is voltage sensitive and draws a low current, and a second circuit portion which draws a high current and is relatively insensitive to supply deviations, comprising a switching circuit alternately connecting said respective circuit portions through respective converters to the supply so that the voltage sensitive circuit is not affected by the loading of the high current circuit. A method is provided for alternately delivering power from a battery source to respective circuit portions of a stimulus delivery system.

Abstract: An electrode for use in combination with a cardiac pacer for endocardial stimulation, having an electrode contact tip at the distal end which has an annular shape with rounded edges for providing a very small stimulating surface, with the largest possible area of such surface in optimal position for direct contact with the heart muscle.

Abstract: A connector device for use in connecting to a electrode pacing electrode, paticularly for connecting a pacer to an electrode where such pacer and electrode are from different manufacturers and are normally not adapted for connection one to another. The connector has a coil which is dimensioned to tightly receive a pronged end of the electrode, the receiving end being further formed in a mating way to receive the electrode so as to prevent current leakage at the situs of connection. The connector is adapted to permit connection or disconnection only as the connector is rotated in one given direction relative to the electrode. In one of the embodiments, the connector is housed in the pacer.

Abstract: An endocardial pacing electrode adapted to be screwed under the inner muscles of the heart in order to be fixed in stimulating contact with the same, the electrode having a spiraled or helically wound tip which is rounded so that the tip engages but does not enter the trabaeculae. A portion of the electrode tip may be covered with an insulating material, leaving a predetermined portion which constitutes the stimulating surface area. The length of the electrode proximal to the tip is hollow to permit insertion of a mandrin, for rotating the electrode around the mandrin and positioning the tip for optimum contact for low stimulation threshold.

Abstract: An amplifier circuit for detecting low level signals of positive or negative amplitude, and for producing an output pulse whenever the input signals exceed a predetermined threshold level. The threshold level, or sensitivity of the amplifier circuit, is established through use of a pair of operational transconductance amplifiers employed as comparators, the reference voltage for each comparator being set through a resistive circuit driven by one or more current sources. The design provides for compensation of amplifier offsets with minimal adjustment requirements, and permits operation with very low current drain.

Abstract: A DC to DC converter with voltage regulator for converting a low level voltage source to a higher level DC, comprising an oscillator circuit with a low resistance starting current path, a rectifier circuit for rectifying the oscillator output, and a regulator for providing a regulated DC output voltage of predetermined level. The oscillator embodies one or more FET devices connected to provide an extremely low DC startup resistance as well as a low cutoff voltage characteristic. With this configuration, the low startup current from the voltage source can initiate switching so that oscillation can occur.

Abstract: An insulated, corrosion-resistant heart pacer is described which incorporates a novel tantalum output means, said output means having disposed on at least the exterior surfaces thereof an anodically-formed substantially continuous Ta.sub.2 O.sub.5 insulating layer. The output means of the pacer or other medical electronic device comprises a tantalum centerpin disposed through a hermetically sealed titanium case, which centerpin is welded to a tantalum feed wire, the combination providing a device in which the Ta.sub.2 O.sub.5 insulating layer reduces the electrical leakage from the tantalum conductor to the titanium case, and whereby the insulating layer disposed thereon further protects the pacer from electrolysis and electrochemical corrosion. An alternate embodiment of the present invention provides tantalum conduit means for electrically connecting an energy source to logic circuitry which is disposed within a hermetically sealed titanium case.

Abstract: An amplifier circuit for detecting low level signals of positive or negative amplitude, and for producing an output pulse whenever the input signal exceed a predetermined threshold level. A first operational transconductance amplifier is used as an amplifier, followed by a pair of operational transconductance amplifiers employed as comparators. The reference voltage for each comparator is set through a resistive circuit driven by one or more current sources. The design minimizes sensitivity drift by providing for compensation of amplifier offsets with minimal adjustment requirements, and provides broad bandwidth operation with very low current drain.

Abstract: A low current drain board bandwidth amplifier circuit for detecting low level signals of positive or negative amplitude, and for producing an output pulse whenever the input signals exceed a predetermined threshold level. A first operational transconductance amplifier is used as an amplifier, followed by a pair of operational transconductance amplifiers employed as comparators. The reference voltage for each comparator is set through a resistive circuit driven by one or more current sources. Feedback means are employed with the amplifier OTA to reduce first stage offset, and sensitivity is established with minimal adjustment requirements.