Abstract: An improved telemetry system for telemetering digital data from an implantable tissue stimulator such as a heart pacemaker. A carrier signal is pulse modulated in accordance with either or both of stored digital data and a digitized electrocardiogram signal, for coupling onto an electrical lead connected directly to the heart. This arrangement facilitates the transmission of substantially higher data rates than previously could be achieved.

Abstract: A rate-responsive pacemaker which includes a conventional programmable pulse generator, a physiological sensor, and a processor is disclosed which generates heart stimulation pulses on demand, or as otherwise programmed, as controlled by a rate control signal which is derived from the physiological sensor. The physiological sensor generates a raw signal which varies as a function of some physiological parameter, such as activity level to provide some indication of whether the heart rate should increase or decrease, and hence whether the pacemaker should change the rate at which pacing pulses are provided. The processor converts the raw signal to the sensor-indicated rate signal in accordance with a selectable transfer relationship which defines the sensor-indicated rate signal as a function of a set of discrete sensor level index signals.

Abstract: A system within an implantable stimulation device and a method for limiting the extent to which any high power consumption modes, such as a rate response mode, can be utilized during low battery periods. A battery threshold detector is utilized to detect when the battery is below a predetermined threshold. The implantable stimulation device then switches from a high current drain mode of operation to progressively lower current drain modes of operation. This configuration allows a significant reduction in current drain at RRT and further prevents the output amplitude from dropping below the capture level and prevents the remaining battery capacity from being rapidly used up.

Abstract: In a rate responsive pacemaker, a physiological sensor is used to sense the physiological needs of the patient's heart and to control both the pacing rate and the A-V interval accordingly. A first adjustment means triggers the timing circuitry to adjust the stimulation rate to a slightly sub-optimal value of cardiac output. A second adjustment means adjusts the A-V interval until hemodynamics are optimized according to the physiological sensor. The improvement in hemodynamics due to the A-V adjustment allows a further decrease in the stimulation rate by the first adjustment means, thereby conserving the limited battery supply.

Abstract: A switched-capacitor, band-pass, programmable amplifier is used as a sense amplifier in an implantable cardiac pacemaker. Switching means are used to switchably connect various capacitors to the same amplifier circuits. Clock generator means are used to generate clock signals that are used to control the rate at which the switching means operates. By programmably selecting the switching rate to be a desired value, the band-pass characteristics and gain of the sense amplifier may be varied. When a pacemaker stimulation pulse occurs, the band-pass characteristics and/or gain of the sense amplifier, may also be automatically varied to improve amplifier recovery time. The rate at which the capacitors are switchably connected to the amplifier circuits, may be selected remotely, thereby allowing the band-pass characteristics to be programmable.

Abstract: A multi-part molded pacemaker connector meets the precise requirements imposed by the VS-1 standard, yet does not require complex nor expensive machining of individual parts. The connector includes a molded body tip and a molded body ring, adapted to be joined together during assembly. The body tip is molded to include a conductive connector block attached to a first conductive ribbon as an integral part thereof. The body ring is molded to include a second conductive ribbon, having a looped end exposed therewithin to provide a precise specified diameter against which a garter spring contact is placed. An inner shoulder molded within the body ring holds the spring contact laterally on one side. During assembly, an annular spacer is pressed into the body ring to restrain the spring contact laterally on the other side. Inner and outer annular seals are also inserted into the body tip and body ring during assembly. After assembly, i.e.

Abstract: A lead-to-pacemaker adapter allows the use of a smaller diameter lead connector than that for which the pacemaker was designed. The pacemaker is shipped with the adapter installed. If the adapter is not to be used, provision is made for its easy removal. The adapter is shown and described for use in a unipolar lead system. The adapter permits direct electrical connection from the terminal pin electrode to the pacemaker connector block and its terminal set screw without the interposition of any intermediate connecting elements.

Abstract: An implantable pacemaker having a unipolar/bipolar lead interchangeability includes lead impedance measuring capability for automatically measuring lead impedance, initiated by the occurrence of predetermined events, such as whenever a programming change is made, whenever capture fails to occur in response to an applied stimulation pulse, whenever the leads are changed, and whenever a significant change of lead impedance is otherwise detected. If a proper impedance measurement is not sensed for a programmed configuration, additional impedance measurements for other possible configurations are made in an ordered sequence in order to determine if an improper lead has been implanted or if a electrode has broken. If an operable configuration is found, signified by a measurement of impedance as expected, the pacemaker continues operation in that configuration, thereby assuring that capture can continue to occur until such time as the problem which has been detected can be corrected.

Abstract: A cardiac defibrillation system and method includes an epicardial electrode for making electrical contact with the epicardium from a position within the pericardial space, an endocardial electrode for making electrical contact with the endocardium of the heart, and means for making electrical contact with the epicardial and endocardial electrodes. The endocardial electrode is inserted transvenously into the heart in conventional manner. The epicardial electrode is also inserted transvenously into the heart, through the heart wall, and into the pericardial space. No open chest surgery is required.

Abstract: A pacemaker and a method of operation thereof are provided for configuring or operating a conventional pacemaker having a plurality of lead electrodes. Each lead can be independently configured for any combination of unipolar or bipolar, pacing and sensing. During a pacing mode of operation, a selected return electrode is switchably connected to the most positive battery potential, V.sub.DD. The return electrode of the packemaker, can selectively be either the pacemaker case or one or more ring electrodes. During a fast discharge time period, which occurs immediately subsequent to the delivery of a pacing pulse, the return electrode is disconnected from V.sub.DD and connected to the proximal side of a coupling capacitor through which the pacing pulse has passed. Also during this fast discharge time period, the proximal side of the coupling capacitor is switchable connected to the most negative battery potential, V.sub.SS.

Abstract: A method and system for positioning a defibrillation electrode within the pericardial space of a mammal is disclosed which includes means for distending the pericardium from the heart by injecting a small volume of fluid into the pericardium. A needle having a lumen therethrough is inserted from a sub-xiphoid or other percutaneous position into the body tissue until a tip thereof punctures the distended pericardium at a selected location. A guide wire is inserted into the pericardium through the lumen of the needle, and while the guide wire remains in the pericardial space, the needle is removed. A sheath is introduced over the guide wire, with the aid of a dilator, and inserted into the tissue until one end thereof is positioned within the pericardium.

Abstract: A method and system for positioning a defibrillation electrode about the heart includes means for placing the electrode in contact with epicardial or pericardial tissue from an inferior vena cava (IVC) access site. A small hole is made in the IVC at the selected access site. A defibrillation lead having the defibrillation electrode near its distal end is transvenously inserted through the IVC and out through the small hole into a chest cavity adjacent the heart. The electrode is then positioned so as to contact the desired cardiac tissue. If pericardial contact is to be made, the distal end of the lead, including the electrode, is looped around the pericardium. If epicardial contact is to be made, an additional small hole is made in the pericardium, and the distal end of the lead, including the electrode, is inserted through the additional hole into the pericardial space, and the electrode is positioned to contact the desired epicardial tissue.

Abstract: A non-programmable automatic implantable cardioverter/defibrillator (AICD) capable of providing programmable thresholds for triggering high energy stimulation pulse(s) from the AICD is coupled to an implantable programmable pacemaker which preferably includes bradycardia support and/or tachycardia support using low enery output pulses. When the low energy antitachycardia pulse(s) from the pacemaker fail to terminate a tachycardia, or whenever other various thresholds, as sensed by programmable sensing circuits of the pacemaker, are exceeded, the high enery pulses from the AICD may be selectively invoked by an AICD trigger circuit included within the pacemaker. Coupling between the AICD and pacemaker is by either a direct electrical connection, or by an indirect connection, such as through the use of narrow pulse sequences generated by the pacemaker which are of insufficient energy to invoke a cardiac response but are of sufficient energy to be sensed by the AICD sensing circuits.

Abstract: A communication system includes self-test means for automatically testing its performance. The communication system is adapted for use between an implantable device, such as a pacemaker, and an external device, such as the pacemaker's programmer. The communication system includes in the external device a transmitter circuit for transmitting an output signal through an antenna, and a receiver circuit for receiving an input signal through an antenna. A driver circuit controls the operation of the transmitter circuit. A microprocessor, connected to the driver circuit, controls the information content and timing of the transmitted output signal. A bandpass filter and AM demodulator process the input signal received through the receiver circuit. A multiplexer selectively allows one of a plurality of status signals from throughout the communication system within the external device, including the demodulated signal obtained from the AM demodulator, to be connected to the microprocessor.

Abstract: An automatically adjustable blanking circuit and method of generating an adjustable blanking interval for use with a dual channel implantable pacemaker includes means for generating a basic blanking interval for a first channel of the pacemaker each time a stimulation pulse is generated on a second channel. The basic blanking interval includes a first absolute refractory portion and a second relative refractory portion. During the absolute refractory portion, the sensing circuits of the first channel are disabled. During the relative refractory portion, the sensing circuits of the first channel are enabled and any activity sensed in the first channel is considered to be crosstalk or noise and the basic blanking interval is retriggered. Retriggering of the basic blanking interval continues for so long as activity is sensed in the first channel during the relative refractory portion of each retriggered basic blanking interval, up to a maximum blanking interval.

Abstract: A device for use as a self-oscillating Class D transmitter is disclosed which uses feedback to maintain the oscillation at the resonant frequency of the device, thereby optimizing the efficiency of operation and overcoming the frequency mismatching inherent in previously known transmitters. The device uses a series LC combination which is driven by a comparator and a tri-state logic driver, with a feedback loop using a differentiator used to switch the polarity of the square wave generator. The system thus self-oscillates at the resonant frequency of the capacitor and inductor, even when the inductance of the inductor is varied by the inductor coming into close proximity to another inductor.

Abstract: A digital phase-locked looped generates a clock signal synchronized with a carrier signal modulated by amplitude shift keying (ASK). During periods when no carrier signal is present, the generated clock signal coasts at the frequency of the carrier signal most recently present, rather than trying to phase-lock on noise. A binary controlled digital oscillator generates the clock signal. A phase detector determines the difference between the phase of the carrier signal, when present, and the local clock signal. When the average amplitude of the carrier signal exceeds a prescribed threshold level, the phase detector output is sampled and passed to an integrator circuit, where the phase difference is integrated. The output of the integrator circuit is applied to a pulse generator, causing the pulse generator's duty cycle to change proportionally.

Abstract: A high speed digital telemetry system (10) includes a transmitter (12) and a receiver (14), at least one of which is adapted for use in an implantable device. The transmitter includes a data encoder (14), modulator (16), transmitting coil (20), and transmitting coil drive circuit (18). The data encoder examines prescribed incoming data bits and prior encoded data bits, generating an encoded data stream (36) that includes a data transition only when a prescribed correlation is noted amongst the examined bits. The modulator modulates a carrier signal (34) with the encoded data stream, causing a phase reversal of the carrier at each data transition of the encoded data stream. The transmitting coil drive circuit applies the modulated carrier (38) to the transmitting coil. The receiver includes a receiving coil (22) and associated amplifier (24) and bandpass filter (26) for detecting the transmitted modulated carrier.

Abstract: An atrial rate based programmable pacemaker including means for preventing the heart from being paced at an upper rate limit for prolonged periods of time is disclosed which paces the heart at a rate that follows or tracks the atrial rate up to the upper rate limit of the pacemaker, at which point the pacemaker stimulates the heart at the upper rate limit, but also continues to monitor the atrial rate. If the monitored atrial rate exceeds a second upper rate limit, a fast atrial arrhythmia or tachycardia condition is deemed to exist, and the pacemaker automatically switches from its existing mode of operation to an alternate mode of operation in an attempt to break or terminate the fast atrial condition. Alternate embodiments include using an external activity or physiological sensor to control the pacing rate in the new pacing mode, and the inclusion of means for periodically verifying that atrial sensing is occurring, and means for automatically adjusting the sensitivity of the atrial channel as required.

Abstract: A device for use as a rate-responsive pacemaker is disclosed in which the pacing interval is controlled by the amount of energy contained in a raw signal generated by a suitable physiological sensor and processed by an energy converter to generate an output energy signal coupled to the pacemaker control circuits to adjust the pacing interval. The energy converter may be a rectifying amplifier and an integrating circuit, a voltage controlled oscillator whose frequency is measured over a suitable time interval using a time interval generator and a counter with the output of the counter being used by the control circuits of the pacemaker to vary its pacing interval, or means for measuring energy content of the raw signal and storing that measurement in memory and periodically processing it to alter the transfer characteristics of the rate-responsive pacemaker.