Abstract: An annunciator is provided for an organ stimulating system which is implantable in the body of a patient. A stimulus signal generator such as an implantable cardioverter defibrillator which includes an energizing capacitor is encased in a housing for imparting an electrical stimulation signal to an organ, such as a heart, to be stimulated. The signal generator includes a sensor for sensing at least one of a plurality of physiological characteristics and apparatus for generating an electrical signal corresponding to the sensed physiological characteristic. A vibration generator responsive to that electrical signal is then operable to impart to the housing a subaudible vibration, that is, one having a frequency less than about 250 hertz, which is detectable by the patient.

Abstract: An implantable cardiac stimulation device includes a system for detecting noise in an electrogram signal. The system for detecting noise generates an event signal when the electrogram signal exceeds a threshold. A timer times a refractory time period responsive to an event signal. During the refractory time period, a zero crossing detector generates a zero crossing signal when the electrogram signal transitions between positive and negative values. A counter counts the zero crossing signals during the time period and a comparator determines if the counter reached a predetermined count during the time period. If the counter exceeds a programmable count, a noise detection flag is set and the controller is alerted to the presence of noise in its input signal.

Abstract: A Holter-type monitor system includes a remotely located data receiving device, an analyte sensor for producing signal indicative of a characteristic of a user, and a Holter-type recording device. The Holter-type recording device includes a housing, a sensor connector, a processor, and a data port. The sensor connector receives the produced signals from the analyte sensor. The processor is coupled to the sensor connector and stores the signals from the analyte sensor for delivery to the remotely located data receiving device. The recording device is coupled to the processor for downloading the stored signals to the remotely located data receiving device. The data receiving device may be a characteristic monitor, a data receiver that provides data to another device, an RF programmer, a medication delivery device (such as an infusion pump), or the like.

Abstract: In an ICD, a highly efficient biphasic defibrillation pulse is generated by switching at least two charged capacitors, e.g., three capacitors, from a parallel connection to various combinations of a parallel/series connection or a series connection during the first phase of the defibrillation pulse. Such mid-stream parallel/series connection changes of the capacitors steps up the voltage applied to the cardiac tissue during the first phase. A stepped-up voltage during the first phase, in turn, gives an extra boost to, and thereby forces additional charge (current) into, the cardiac tissue cells, and thereby transfers more charge to the membrane of the excitable cardiac cell than if the capacitors were continuously discharged in series. Phase reversal is timed with the cell membrane reaching its maximum value at the end of the first phase.

Abstract: An implantable cardiac device is disclosed having a converter that provides a digital electrocardiogram signal to a controller which is stored in memory or transmitted via the telemetry circuit in an improved compressed fashion. The improved compression scheme comprises sampling the electrogram signal, transmitting the starting value in an uncompressed format followed by a plurality of delta signals in a compressed format. The delta signals may be determined by subtracting successive signals or by subtracting a predicted value from the current value. In either case, the delta signal is then transmitted in a truncated number of bits, e.g., 2 or 4 bits. When the delta signal is too large to be represented in the compressed number of bits, the controller then provides an indicator signal followed by the delta signal in the uncompressed format. In addition, whenever successive delta signals are below a minimum threshold (e.g., zero), they may be compressed into a count.

Abstract: An improved sensor and related method for multi-axial measurement of motion for an implantable medical device is disclosed. The sensor has a wide variety of applications, including use as a cardiac wall motion sensor or a physical activity sensor. The sensor includes first and second conductors over which the motion measurements are made. A first transducer provides a first motion measurement indicative of sensor acceleration during a first phase, while a second transducer provides a second motion measurement indicative of sensor acceleration during a second phase. The first and second transducers are connected in parallel so as to provide the first and second motion measurements to an implantable medical device over the first and second conductors. The first and second phases are non-overlapping periods of time so that the motion measurements from each transducer are time division multiplexed. The sensor provides motion measurements that may either be compensated or uncompensated for temperature effects.

Abstract: An antitachycardia stimulation device that automatically adjusts its detection rate threshold as a function of a sensed physiological parameter indicative of cardiac rate. The implantable antitachycardia stimulation device includes heart rate detection circuitry and antitachycardia therapy circuitry for applying a specific antitachycardia therapy in the event that the detected heart rate falls within at least one tachycardia rate zone. The tachycardia rate zone is defined by a lower threshold limit, and may also be defined by an upper threshold limit if more than one rate zone is used. The lower threshold limit is automatically adjusted as a function of an independently sensed physiological parameter that predicts a normal or natural change in the heart rate. If more then one rate zone is used, other threshold limits may also be adjusted automatically as a separate function of the same sensed physiological parameter.

Abstract: A system for delivering low pain cardioversion shocks to the heart wherein the system provides a waveform to the heart for cardioversion purposes to result in less stimulation of sensory nerves surrounding the heart. In one embodiment, the system includes a controller and a plurality of controlled switches that can be configured so that the heart receives a waveform through one or more resistors from a capacitor. The controller is configured to manipulate the switches so that the waveform that is applied to the heart is applied for more than 10 milliseconds so that the ratio of stimulation of the cardiac cells to the stimulation of sensory cells is approximately one. In another embodiment, the controller configures the switches so that a first capacitor discharges to charge a second capacitor through a resistor wherein the second capacitor is in parallel with the heart.

Abstract: A microprocessor-controlled implantable cardiac stimulating device having a normal mode, an intermediate mode, and a backup pacing mode is provided. The device switches from one mode to another in response to the detection of any one of an address error, parity error, opcode error, or watchdog timer error. The microprocessor is shut down during the delivery of a cardioversion or defibrillation shock in order to prevent signals produced by the microprocessor from being subjected to transient electrical signals. The interrupt registers of the microprocessor are also disabled during the delivery of a cardioversion or defibrillation shock. In an alternative embodiment, an implantable cardiac stimulating device is provided with redundant microprocessors in order to detect malfunctions of the microprocessors.

Abstract: A cardiac event and arrhythmia detection system and method detects arrhythmic cardiac activity or other information from an electrogram signal of a heart. The system senses the electrogram signal through an electrogram lead, preliminarily processes the signal, and converts it to a plurality of discrete digital signals, each of which represents the magnitude of the electrogram signal at a prescribed sample time. The discrete digital signals are applied to both a cardiac event detector which has a dynamic threshold which is programmably adjustable so that T-waves are not sensed and a morphology detector. The morphology detector detects selected changes in the morphology (shape) of the electrogram signal, wherein such changes automatically control the sensitivity (gain and/or threshold) used to detect cardiac events. The occurrence of a prescribed amount of change in the detected morphology over time indicates the occurrence of a prescribed arrhythmic cardiac condition.

Abstract: Implantable leads incorporating accelerometer-based cardiac wall motion sensors, and a method of fabricating such leads, are provided. The cardiac wall motion sensors transduce accelerations of cardiac tissue to provide electrical signals indicative of cardiac wall motion to an implantable cardiac stimulating device. The implantable cardiac stimulating device may use the electrical signals indicative of cardiac wall motion to detect and discriminate among potentially malignant cardiac arrhythmias. In response to a detected abnormal cardiac rhythm, the cardiac stimulating device may deliver therapeutic electrical stimulation to selected regions of cardiac tissue.

Abstract: A microprocessor-controlled implantable cardiac stimulating device having a normal mode, an intermediate mode, and a backup pacing mode is provided. The device switches from one mode to another in response to the detection of any one of an address error, parity error, opcode error, or watchdog timer error. The microprocessor is shut down during the delivery of a cardioversion or defibrillation shock in order to prevent signals produced by the microprocessor from being subjected to transient electrical signals. The interrupt registers of the microprocessor are also disabled during the delivery of a cardioversion or defibrillation shock. In an alternative embodiment, an implantable cardiac stimulating device is provided with redundant microprocessors in order to detect malfunctions of the microprocessors.

Abstract: An implantable cardiac device for providing cardioversion and defibrillation therapies is provided, which forecasts time-to-therapy based on battery voltage degradation and provides an enhanced energy shock in the event a predetermined threshold time is reached. The device also monitors elapsed time-to-therapy to determine whether the predetermined threshold time is exceeded and sets the energy content of the therapeutic shock accordingly.

Abstract: Implantable leads incorporating accelerometer-based cardiac wall motion sensors, and a method of fabricating such leads, are provided. The cardiac wall motion sensors transduce accelerations of cardiac tissue to provide electrical signals indicative of cardiac wall motion to an implantable cardiac stimulating device. The implantable cardiac stimulating device may use the electrical signals indicative of cardiac wall motion to detect and discriminate among potentially malignant cardiac arrhythmias. In response to a detected abnormal cardiac rhythm, the cardiac stimulating device may deliver therapeutic electrical stimulation to selected regions of cardiac tissue.

Abstract: An implantable cardioverter-defibrillator (ICD) adaptively adjusts the refractory period and sensitivity setting of its sensing channel in order to optimally detect depolarization signals indicative of intrinsic cardiac rhythm or tachycardias, or depolarization signals indicative of fibrillation. In one embodiment, the ICD utilizes first and second depolarization signal processing channels, each having first and second refractory periods and first and second sensitivity settings, respectively. The sensitivity settings of the first processing channel are adaptively adjusted to sense normal depolarization signals and tachycardias. The sensitivity settings of the second processing channel are adaptively adjusted to sense fibrillation. Both the first and second refractory periods begin following either a paced depolarization or a sensed depolarization.

Abstract: An external diagnostic/programming device is disclosed which includes means for both displaying intracardiac electrical signals sensed and telemetered from an implantable pacemaker in real-time, and for storing the intracardiac electrical signals for subsequent retrieval and analysis. The subsequent analysis selectively includes processing means for processing the signals off-line (i.e., not in real-time), using various signal processing strategies, such as digital filtering and frequency domain spectral analysis. The off-line signals may also be recursively processed in order to enhance the detection of a particular physiologic phenomena manifested by, but not readily discerned within, the unprocessed real-time signals.

Abstract: An apparatus for treating arrhythmias of the human heart includes a defibrillator, and an arrangement for providing passive diode multiplexing between two patches for bidirectionally passing an electric current through a human heart. The arrangement is formed by connecting a cathode of a first diode to a first mesh electrode on a first conductor and connecting an anode of a second diode to a second mesh electrode on the first patch. An anode of the first diode and a cathode of the second diode are then connected to a lead. An identical diode arrangement is provided for the second patch.

Abstract: A patch electrode including a generally oval-shaped metallic mesh affixed to a polymer insulation backing and an insulation frame, and further including a plurality of specially designed lattices which divide the metallic mesh into a plurality of windows or apertures. The windows effectively act as smaller electrodes distributing the higher current densities inward from each of their own individual edges.

Abstract: An implantable cardioverter-defibrillator (ICD) provides a tiered therapy designed to automatically terminate tachyarrhythmias using the least aggressive therapy possible while reducing the "time-to-therapy." The tiered therapy first applies a first tier of therapy (e.g., antitachycardia). If unsuccessful, the tiered therapy next applies a second tier of therapy (e.g., cardioversion pulse with a pulse of moderate energy). If unsuccessful, the tiered therapy finally applies a third tier of therapy (e.g., a high energy pulse). So that more aggressive (higher energy) tiered therapies may be applied as early as possible following the failure of a less aggressive (lower energy) therapy, the ICD begins charging one or more high voltage capacitors of the ICD in parallel with the application of the less aggressive therapy, and/or in parallel with the verification interval immediately following a prior therapy attempt during which the ICD attempts to verify the successful termination of the tachyarrhythmia.

Abstract: An analyzer-programmer system (30) for use with an implantable medical device, such as a cardiac pacemaker (20). The system facilitates non-invasive communications with the implantable device and makes analysis of the operation of the implantable device easier to understand and perform. The system includes conventional processor means (42) for processing a sequence of stored instructions stored in programmable read-only memory, or ROM (40). The ROM, although designed to be accessed through predefined page of information, and blocks within such pages, is configured to allow in-page addressing within any of a plurality of pages in a linear fashion. Programmed intervals to be sent to the implantable device are displayed by the system in tabular form or as scaled time-lines or bars (FIG. 9A), with each separate interval beginning and ending in proper timed sequence, thereby providing a prediction of the expected performance. Such programmed intervals can overlay or sidelay measured performance (FIG.