Abstract: An implantable electrical bone growth stimulator having a case made of metal, a current source in the case, an anode and at least one cathode lead electrically connected to the current source and exiting the case. The case has a thin, flat-sided shape with a rectangular cross-section. The current source is a circuit board and electrical components that are arranged on the circuit board to form a completed assembly positioned completely within the case, and the anode is an area of the case that is platinum plated.

Abstract: A combined telemetry system and magnetic field sensor for use in an implantable medical device. The telemetry system includes a conventional resonant circuit for transmitting and receiving data. The resonant circuit has a coil which is also used to sense the presence of a magnetic field exceeding a threshold value. The resonant frequency varies with the strength of the magnetic field which passes through the coil. Periodically, the resonant circuit is energized, and during a sensing window of predetermined duration which then immediately follows the voltage across the coil is examined for a predetermined number of zero crossings. That number of zero crossings will occur only in the presence of a magnetic field whose amplitude exceeds the threshold value. It is possible to achieve a sensitivity in such a system which is comparable to that of conventional miniature reed switches.

Abstract: There is disclosed a bridge circuit which finds particularly advantageous use in medical prostheses which can be programmed externally and which can transmit telemetry signals. The entire circuit is implemented on a single CMOS integrated circuit. Depending upon the values of two control bits, the bridge circuit functions to derive a powering potential from an externally transmitted signal, with or without regulation. Externally transmitted programming signals are detectable, and telemetry signals can be transmitted from the chip as well. There is no active switching of bridge devices during power rectification mode, and instead they are biased on continuously. This allows the rectifier to operate at carrier frequencies as high as several megahertz. All of this is achieved by using conventional CMOS processing techniques, without requiring any extra diffusion steps.

Abstract: A delta modulator for controlling time-domain processing of sensed signals, and particularly internal physiological signals. The delta modulator includes two constant current sources both of which are on continuously, but only one of which is connected to the input capacitor at any given time. The two constant current sources are self balancing. Periodically, the two current sources are connected simultaneously to a control capacitor, the potential across which is thus a function of the relative current source amplitudes. The potential across the control capacitor is used in a feedback circuit to control the amplitude of at least one of the current sources so that the two sources are made to have equal amplitudes. Preferably, the control capacitor is an on-chip capacitor whose effective capacitance is increased by the Miller effect.

Abstract: The signal sensed on a heart pacer electrode is converted by a delta modulator to a sequence of samples of 0 and 1 bit values. The resulting bit sequence is delayed, and the original bit sequence and its delayed version are continuously subtracted from each other in a clocked up/down counter to derive a count. When the count reaches a threshold value, three different recognition logic circuits are triggered and they then operate for two milliseconds. One circuit recognizes a beat if the count does not drop below another, lower threshold value during the timing interval. A second circuit detects a beat if the count remains above the threshold level for at least 50% of the time during the timing interval. The third circuit detects a beat by operating directly on the delta modulator output bit sequence; it checks whether bits of the value indicative of the triggering event predominate over bits of the opposite value during the timing interval.

Abstract: A tachycardia control pacer for which placing a magnet over the patient's chest results in the generation of two pulses, the time separation between which is an indication of the battery potential. Application of the magnet in this way also holds the device off, after the two pulses are generated, so that if the device is causing him discomfort the patient can temporarily disable it until the physician can program it off. Application of a magnet to the patient's chest, or programming of the device, resets two scanned inter-pulse time intervals to the values programmed by the physician. The next scanning begins with the programmed time values. In this way the physician, after inducing tachycardia, can verify the programmed time parameters rapidly by observing the patient's ECG waveform, without having to wait several minutes until scanning from the previously retained successful values would otherwise progress to the programmed values.

Abstract: A tachycardia control pacer for which placing a magnet over the patient's chest results in the generation of two pulses, the time separation between which is an indication of the battery potential. Application of the magnet in this way also holds the device off, after the two pulses are generated, so that if the device is causing him discomfort the patient can temporarily disable it until the physician can program it off. Application of a magnet to the patient's chest, or programming of the device, resets two scanned inter-pulse time intervals to the values programmed by the physician. The next scanning begins with the programmed time values. In this way the physician, after inducing tachycardia, can verify the programmed time parameters rapidly by observing the patient's ECG waveform, without having to wait several minutes until scanning from the previously retained successful values would otherwise progress to the programmed values.

Abstract: There is disclosed a heart pacer in which the sensed signal is processed in the time domain rather than the frequency domain. A delta modulator operates directly on the sensed electrogram signal, without any intervening filtering, to derive a sequence of bits whose states represent increments or decrements in the sensed signal amplitude. Decisions as to cardiac activity are based on the sequence of bit values thus generated. The particular delta modulator disclosed is highly advantageous in that it allows highly accurate tracking and representation of the sensed signal.

Abstract: A transmitter for a medical prosthesis which is highly efficient, and also permits rapid starting and stopping so that the same coil can be used for both transmission and reception without undue delays between the two modes of operation. During transmission, a tuned circuit, consisting of the coil and a capacitor, is pumped at a frequency equal to the resonant frequency. Transmission is concluded when almost all of the energy in the tuned circuit is in the form of a voltage across the capacitor and when the current through the inductor is approximately zero. This allows the inductor to be used immediately for reception. At the start of the next transmission cycle, the voltage which is maintained across the capacitor is used to initially energize the tuned circuit.

Abstract: A heart pacer in which the magnitude of the end-of-life test current source is programmable. This effectively allows the physician to program the condition which will control a switch-over to end-of-life operation. It also allows the physician to override end-of-life operation after it initially takes place following a failing of the end-of-life test. The pacer also includes an additional end-of-life test involving the continuous monitoring of the supply potential and a switch-over to end-of-life operation should the pacer powering potential momentarily fall below a threshold level.

Abstract: A delta modulator for a heart pacer which not only allows sensed signals to be monitored, but also facilitates measurements of DC operating potential levels. The DC levels, and changes in them, can be measured accurately by equilibrating the modulator with the application to it of a suitable reference potential as the initial step in a measurement sequence. This same technique allows small signal variations to be tracked even if they are superimposed on large signals.

Abstract: A heart pacer connector assembly for two bipolar electrode lead proximal terminations, each having a forward pin contact and a rearward annular ring contact. Two in-line pairs of metallic termination blocks are connected by four wires to respective lead-through terminals. At least two fluid-insulating, metal-free plastic parts (molded without embedding termination blocks in them) are then slid on the assembly to insulate the termination blocks and to provide a pair of insertion bores for the proximal terminations. The plastic parts are shaped to lock onto capped studs provided on the case, and the plastic parts are sealed to each other. Each termination block for an annular ring contact may consist of a simple hollow cylinder having three equally spaced circumferential cuts, with a contact wire being wrapped around the cylinder, sitting in the cuts and extending into the cylinder bore, and being connected directly to the respective terminal.

Abstract: A dual-chamber heart pacer whose ventricular pacing rate is closely matched to the physiological requirements of the patient. A "true" atrial rate is determined by counting over a 3-second interval the number of sensed atrial beats, including those which occur during atrial refractory periods. When the atrial rate rises to a threshold level, the ventricular pacing rate decreases gradually from the Wenckebach rate to a fall-back rate independent of atrial sensing. During this decline, atrial pacing pulses may be generated simultaneously with ventricular pacing pulses in an effort to terminate tachycardia. The controlled decline in ventricular pacing rate begins after a 3:2 block has resulted, but before a 2:1 block would otherwise result. The fall-back rate is higher than the standby rate to compensate for the lack of atrial pacing when the system operates at the fall-back rate.

Abstract: A tachycardia control pacer in which at least one scanned pulse is generated following each tachycardia confirmation, and the last-used pulse timing is retained following the next tachycardia termination for subsequent first use following the next tachycardia confirmation. The tachycardia termination detecting circuit does not respond to the time interval between at least the first two heartbeats following a generated pulse, to prevent a false determination of tachycardia termination due to the excessive pauses which sometimes occur immediately after pacing despite the fact that tachycardia has not terminated.

Abstract: There is disclosed an implantable bone growth stimulator whose direct-current output can be monitored. Rather than to interrogate the device, e.g., by using a control magnet as in the heart pacer art, the device continuously transmits pulses of electromagnetic energy at a rate proportional to the current being delivered. The continuous transmission expends no more than about five percent of the total power. Instead of using an electrode lead as an antenna for radiating the pulses, a separate coil inside the device is utilized so that the therapeutic current itself is in no way affected by the pulse transmission. Effective transmission is achieved despite the fact that the device is hermetically sealed in a titanium case. Also included is an electronic switch for drastically limiting power drawn from the battery until implantation takes place, in order to provide an extended shelf life.

Abstract: There is disclosed on external programmer for use with heart pacers of two different types. Depending on the reed orientations in the two types of pacers, the magnetic flux generated by the programmed has to be in one of two orthogonal directions through the pacers. A pair of parallel coils is provided. A switching circuit switches the current direction through one of the coils so that the two coil fluxes aid or oppose each other, thus giving rise to orthogonal fluxes through pacers to be adjusted. A pacer of either type can thus be adjusted without the physician having any concern for the reed/programmer orientations.

Abstract: A cardiac pacemaker electrode lead comprising an electrode tip, an electrical conductor electrically coupled to the electrode tip, an insulative sheath covering a portion of the electrical conductor, and a molding member for covering the uninsulated portion of the electrical conductor and including a distal end for forming a first lap joint with the electrode tip and a proximal end for forming a second lap joint with the insulative sheath. Foldable tines are formed on the molding member and when unfolded extend at an angle from the molding member to anchor the electrode tip in trabecular muscles inside the heart. When folded, the tines are received in a recessed portion of the molding member such that the tines are substantially flush with the exterior surface of the lap joints.

Abstract: There is disclosed an implantable tissue-stimulating prosthesis, such as a cochlear prosthesis, which can not only be implemented in single-chip form, but which also permits great flexibility in stimulation strategy and data transmission format. Only sixteen electrodes are required for stimulating fifteen different sites. Each site is stimulated by a biphasic pulse under control of two adjacent electrodes whose polarities are reversed in the middle of the site stimulation cycle. Although the transmission scheme requires a pulse-width modulation format, the precise form of the format can be varied in order to accommodate widely different stimulation strategies. For example, only a single site may be stimulated during each transmission frame or multiple sites may be stimulated during the same frame. Although only one site can be stimulated at any instant of time, the system cycling is so fast that "simultaneous" site stimulations are perceived.

Abstract: An improved pacer for controlling tachycardia. Following tachycardia confirmation, a burst of at least three stimulating pulses is generated. The time intervals between successive pulses decrease by a fixed decrement; thus the rate of the pulses increases during each cycle of operation, the burst being more accurately characterized as a "chirp". The first pulse is generated following the last heartbeat which is used to confirm tachycardia at a time which is actually dependent on the rate of the heartbeats in the tachycardia episode; the time delay between the last heartbeat and the first pulse in the chirp is equal to the time interval between the last two heartbeats, less the fixed decrement which characterizes successive time intervals between stimulating pulses. Because successive pulses are generated at an increasing rate, and because the first pulse is generated at a time which is actually dependent upon the tachycardia rate, there is a greater likelihood that tachycardia termination will be achieved.

Abstract: A cardiac pacemaker electrode including an electrode tip having an external surface with a concave region formed therein to increase the pacing impedance thereof. Further, the external surface of the electrode tip is roughened, for example by abrading with a jet of glass beads projected under pressure, to increase the microsurface area of the electrode tip and to reduce the sensing impedance thereof.