Abstract: A programmable pacemaker pulse generator capable of operating in several atrial and ventricular pacing modes having atrial and ventricular sense amplifiers and output circuits and programmable memory and clock controlled digital timing circuits for selectively delivering stimulating pulses to the heart in an atrial synchronous mode of operation. The ventricular sense amplifier has a blanking and refractory period following the sensing of a ventricular heartbeat or the occurrence of a stimulation pulse. Delay means operatively connected to the atrial sense amplifier operate to trigger the generation of a ventricular stimulating pulse after an A-V delay interval following a sensed atrial depolarization. The A-V delay interval is lengthened by means responsive to the detection of two or more ventricular depolarizations without an intervening atrial depolarization, so as to avoid the application of a ventricular stimulating pulse into the vulnerable period (or T-wave) of the heart.

Abstract: A body implantable stimulator having an output capacitance that is periodically charged to a predetermined energy level and discharged through an electrode coupled to body tissue. The discharge pulse width is controlled by a semiconductor switch and after a short delay the capacitor is recharged rapidly to its original charge. The recharge current is regulated by a differential circuit responsive to the voltage on a reference capacitor and the output capacitor, both capacitors being coupled to the active electrode.

Abstract: Pacer output circuitry for providing biphasic stimulation pulses to heart tissue at a voltage twice the supply voltage. Additionally, the circuit may be configured to sense the intracardiac electrogram in a unipolar or bipolar configuration.

Abstract: A programmable pacemaker pulse generator capable of operating in several atrial and ventricular pacing modes, having atrial and ventricular sense amplifiers and output circuits and programmable memory and clock controlled digital timing circuits for selectively delivering stimulating pulses to the heart in an atrial synchronous mode of operation. The ventricular sense amplifier has a blanking and refractory period following the sensing of a ventricular heartbeat or the occurrence of a stimulation pulse. Delay means are operatively connected to the atrial sense amplifier operate to trigger the generation of a ventricular stimulating pulse after an A-V delay interval following a sensed atrial depolarization.An atrial blanking interval extends for the A-V delay interval and until after the expiration of the ventricular blanking interval. Programmable upper date intervals are also provided.

Abstract: A programmable pulse generator capable of operating in several atrial and ventricular pacing modes having atrial and ventricular sense amplifiers and output circuits, programmable memory and clock controlled digital timing circuits and a depletable power source. End-of-life sensing circuits detect first and second end-of-life depletion levels. Magnet activated end-of-life test circuitry responds to the presense of none, one or both of the end-of-life depletion level signals to alter the operating modes and pacing rates to indicate the orginally programmed mode and the level of depletion to an observer. Preferably, the pulse generator is operated in the asynchronous DOO or VOO modes and at non-programmed test rates to provide the indication.

Abstract: An implantable medical device to deliver cardioverting energy to cardiac tissue in synchrony with detected ventricular depolarizations. The energy renders refractory, areas of the heart associated with a reciprocating or automatic tachycardia, thus reverting these tachyarrhythmias to normal sinus rhythm without the risk of stimulating the heart during the vulnerable portion of repolarization.

Abstract: A demand cardiac pacemaker of the type having sense amplifier circuitry for detecting the occurrence of natural heart activity which establishes a first level representative of sensed extraneous repetitive noise and a second level greater in absolute value than the reference by an amount representative of sensed heart activity. Circuitry differentially responsive to the difference between the reference and second level detects the occurrence of natural heart activity. The sense amplifier circuitry is blanked, that is disconnected from the terminals coupled to the heart, for a blanking interval following stimulation to avoid saturation of the sense amplifier stages and the erroneous detection of a pacing stimulus. Any reference level voltages developed by extraneous repetitive noise are retained during blanking to prevent the differential circuitry from interpreting the noise signal sensed at the end of the blanking interval as a heart signal.

Abstract: A marker channel telemetry system for use with a pacemaker or other medical device for transmitting event identifying codes to a remote receiver to indicate the occurrence of specific events such as sensed and paced events in a dual chamber pacemaker. The structure of the system includes latches to store event information and for forming the marker codes. The system also includes a serial telemetry transmitter for transmitting the data to the remote receiver.

Abstract: A multiple-mode pacer which automatically switches from an atrial synchronous mode to a ventricular inhibited mode when the intrinsic atrial rate drops below a preset hysteresis rate. This mode switching prevents atrial bradycardia from resulting in the delivery of closely spaced ventricular stimulating pulses.

Abstract: A lead having multiple electrodes which is transvenously implanted for use in standby defibrillation of patients having a high risk of ventricular fibrillation. The lead employs four electrodes. The two distal electrodes have a spacing for optimal measurement of impedance changes due to mechanical contractions. This impedance measurement is used for mechanical sensing of normal cardiac activity. The electrode at the very distal tip terminates in a hemispherical shape. Two proximal electrodes are closely spaced and located at a distance from the two distal electrodes which ensures their placement within the superior vena cava whenever the distal electrodes are placed within the right ventricular apex. The body of the lead uses drawn brazed strand conductors wound triaxially for maximum flexibility, minimum cross-sectional area and the required high current carrying capability. At the proximal end of the lead, three connectors are used to electrically couple the lead to an implantable pulse generator.

Abstract: An electrode for a body implantable lead having a semiconductor surface for the coupling of electrical signals to the body tissue. A first approach uses several materials of differing conductivities. These materials are arranged in layers such that the material having the lowest conductivity is in direct contact with body tissue. The layers are then added in increasing order of conductivity. The intersection of two materials may be abrupt or may be a smooth transition fashioned by a combination of the two materials. The second approach provides an abrupt transition from the highly conductive materials within the lead body to a semiconductor material having direct exposure to the body tissue. The conductor within the body implantable lead is preferably fabricated using drawn brazed strand coils arranged in multifilar fashion. The conductor coils are insulated using a polyurethane sheath.

Abstract: A pacer having an upper and lower rate limit system for preventing pacer malfunction from producing pacer output pulses above or below preset maximum and minimum rates.

Abstract: A physiological event detector including apparatus for receiving and detecting an electrical signal corresponding to a physiological event. The apparatus produces a logic level output when the input signal meets both passband energy criteria and time duration criteria. The structure of the invention includes a filter for selecting the passband criteria and digital timing circuitry for determining how long the passband signal exceeds a minimum energy threshold.

Abstract: Memory control circuitry for use in a pacemaker or other medical device for setting volatile memory to a known configuration if the battery voltage and/or current drops below the level required for reliable operation of the memory devices.

Abstract: A dual pace--dual sense cardiac pacemaker pulse generator having ventricular and atrial sensing and pulse generating means interconnected by circuit means to cause the atrium to be stimulated in the event that a natural atrial contraction is not sensed within a certain time from the last ventricular stimulus or natural contraction and the ventricle to be stimulated in the event that a naturally ventricular contraction is not sensed within a further time from the last atrial contraction or stimulus.

Abstract: A CMOS inverter is used to compare pacemaker battery voltage to a referenced voltage. When the reference voltage exceeds the measured battery voltage, the inverter changes state to indicate battery depletion.

Abstract: An atrial pacemaker having an atrial pacing rate adjusted to correspond to a detected ventricular heart rate to maintain A-V synchrony in a range between a minimum and maximum pacing rate. Sensed ventricular depolarizations not associated with a preceding atrial pacing stimulus cause the atrial pacing rate to be increased. When A-V synchrony is restored at a higher rate, the rate is decreased. Underdrive stimulation to treat pathologic tachycardia is achieved as the atrial pacing rate is increased in steps to the maximum pacing rate, normally lower than typical tachycardia rates.

Abstract: A controlled feeder block for use in a telecommunications interface provides a plurality of slidable switching assemblies, each of which is selectively used to connect an in-feeder wire to either an out-feeder wire or a wire receiving terminal.

Abstract: A display device having a plurality of information symbols for each light source such as an LED chip. The upper surface of each LED chip is divided into several light-emitting areas by a patterned array of electrically isolated, spaced electrodes. The LED chips are mounted to a substrate and can be selectively activated by a beam lead tape, which is also mounted to the substrate. A cover for the display forms thin, reflective light channels, each of which extends laterally from a light-emitting area to one or more optical openings in the cover. The optical openings form the information symbols. The lateral channels direct emissions from the LED chip to the openings via multiple reflection and optical dispersion to uniformly illuminate the openings.

Abstract: A copy machine for reproducing original size, reduced or magnified copies of an original document is disclosed. The original document is supported on a transparent support surface. An optical scanning system is moved past the original document and an image of the document is transmitted to a photosensitive surface which is moved at constant speed. The speed of the optical scanning system is related to the magnification ratio. The scanning system is driven by a plurality of cams mounted upon a common cam shaft. Scanning speed is selected by coupling the scanning system to one of the plurality of cams.