Abstract: An evoked response detector for a heart stimulator determines evoked response in the presence of polarization. The heart stimulator has a pulse generator which produces stimulation pulses of varying amplitudes, and a lead adapted for introduction into the heart of a patient is connected to the pulse generator for delivering stimulation pulses to the heart. The evoked response detector includes measuring and memory circuitry for measuring and storing the electrode signals picked up by the lead in response to the delivered stimulation pulses, at least one of these stimulation pulses having a sufficiently high amplitude for obtaining capture. Each measured electrode signal contains two signal components, one of these signal components being proportional to the amplitude of the associated stimulation pulse and the other signal component being substantially constant, independent of the associated stimulation pulse amplitude.

Abstract: An implantable cardiac stimulation device having an improved multi-level electronic package is disclosed. The multi-lever package includes at least two stacked internal substrates for mounting electronic circuits, a protective lid for protecting the substrates, and an external interconnect structure mounted on the lid which is also capable of mounting electronic components. The interconnection between the at least two internal substrates is achieved by vertically-oriented wirebonds, and the interconnection between at least one internal substrate and the external interconnect structure is achieved by vertically-oriented brazed-on pins which pass through holes in the protective lid. This construction minimizes the planar dimensions of the electronic package and optimizes space in the physiologically-curved portions of the housing.

Abstract: An implantable heart stimulator includes a unit for setting a maximum allowable stimulation rate and an ischemia detector. An analysis unit and control unit and connected to the ischemia detector and to the setting unit for controlling the setting unit so as to lower the maximum allowable stimulation rate in response to the detection of an ischemic state.

Abstract: An ischemia detector includes repolarization sensor which senses repolarization of the heart of a patient and delivers corresponding repolarization signals to a detecting unit and a workload sensor which senses the workload of the patient and delivers corresponding workload signals to the detecting unit. The detecting unit identifies a state of ischemia as existing upon the occurrence of a predetermined relation between sensed repolarization and sensed workload.

Abstract: An electronic package having vertically integrated components placed upon a substrate surface is configured to increase packing density of the components. Integrated circuits which are vertically-stacked and attached to the substrate surface communicate with surrounding components through connection to bond pads on the substrate surface. The bond pads can be placed entirely about a perimeter of the integrated circuits to achieve optimal packing density. Individual bond pads may be shared by two or more integrated circuits by connection therewith. In an alternative embodiment, a separate integrated circuit is attached to the substrate adjacent to the stacked integrated circuits with a row of shared bond pads positioned therebetween. Individual passive or active components may be placed between bond pads for incorporation into the circuit structure.

Abstract: A processing system and method are provided for deriving an improved hemodynamic indicator from cardiac wall acceleration signals. The cardiac wall acceleration signals are provided by a cardiac wall motion sensor that responds to cardiac mechanical activity. The cardiac wall acceleration signals are integrated over time to derive cardiac wall velocity signals, which are further integrated over time to derive cardiac wall displacement signals. The cardiac wall displacement signals correlate to known hemodynamic indicators, and are shown to be strongly suggestive of hemodynamic performance. An implantable cardiac stimulating device which uses cardiac wall displacement signals to detect and discriminate cardiac arrhythmias is also provided.

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 implantable atrial defibrillator analyzes both the atrium and the ventricle to determine an abnormal atrial condition of the atrium and if the ventricle is unstable. Therapy is applied to correct the abnormal atrial condition, such as atrial fibrillation, only if the ventricle is stable, to insure that the therapy does not provoke a ventricular tachyarrhythmia. If the ventricle is unstable, first a process is performed to stabilize it, for example by using a ventricular pacing protocol. After the ventricle is stabilized, the atrial therapy is applied in synchronism with the ventricular events (i.e., in synchronism with either ventricular intrinsic events or ventricular pacing pulses.

Abstract: An implantable cardiac stimulation device, such as a pacemaker or an implantable cardioverter-defibrillator, that includes an accelerometer-based activity sensor that processes one or more signals from the activity sensor to obtain parameters that are indicative of the heartbeat of the patient. The implantable cardiac stimulation device determines when the patient is at rest and the activity sensor provides a signal that corresponds to the acceleration of the sensor due to the heartbeat of the patient. This acceleration signal is integrated over time once to provide a contractility parameter, which is indicative of the contractility of the heart and is integrated over time twice to provide a displacement parameter, which is indicative of the displacement of the heart wall during the heartbeat. This displacement parameter is thereby indicative of the volume of blood pumped by the heart.

Abstract: A method of manufacturing a capacitor for use in an implantable cardiac defibrillator by forming a set of conductive sheets with the same profile having a sacrificial portion. An alignment figure is formed in each sheet, and the sheets are stacked and aligned by registering the alignment figures with each other. The sacrificial portions are removed from each of the sheets, which are secured together and positioned in a capacitor housing. Each sheet may include two major portions joined by the sacrificial portion, so that each major portion may become part of a separate capacitor stack after the sacrificial portion is removed, doubling manufacturing throughput.

Abstract: A pacemaker generates and transmits real-time intracardiac electrogram signals to an external display device for display thereon. Simultaneously, the pacemaker senses a variety of events occurring either within the heart tissue or within the pacemaker itself and transmits signals representative of those events for display, using appropriate marker icons, along with the intracardiac electrograms. In this manner, a physician viewing the intracardiac electrograms is simultaneously apprised of the various events. In one example, events displayed along with the intracardiac electrograms include the detection of atrial and ventricular events occurring within the heart during a non-absolute refractory period following generation of a stimulation signal.

Abstract: An implantable dual-chamber pacemaker programmed to operate primarily in a P-wave tracking mode, where the pacemaker switches to a fallback response at a threshold rate higher than a maximum tracking rate of the pacemaker. When the fallback response is initiated the ventricular pacing rate is progressively reduced to a fallback rate. The pacemaker exits the fallback response when programmable fallback exit criteria are met.

Abstract: A method of manufacturing a capacitor by highly etching a foil sheet, and at selected relief portions of the sheet, reducing the surface area coefficient. An anode sheet is cut from the foil sheet and assembled with other capacitor components. The surface area coefficient may be reduced by coining or mechanically compressing at the selected relief portions, and an oxide layer may be formed on the sheet after coining.

Abstract: An active overload detection and protection circuit for protecting a host device (e.g., an implantable cardiac therapy device) from potential damage due to high voltage transients applied to an I/O node thereof. The protection circuit includes an I/O circuit coupled to the I/O node, the I/O circuit having low-impedance and high-impedance modes, a current overload detection circuit coupled to the I/O circuit which detects a current overload condition induced by a high voltage transient, and which generates an overload detect signal in response, and, a mode changing circuit which changes the mode of the I/O circuit from the low-impedance mode to the high-impedance mode in response to the overload detect signal. The protection circuit further includes a reset circuit which generates a reset signal a prescribed time after the overload detect signal is generated, wherein the mode changing circuit is responsive to the reset signal to change the mode of the I/O circuit.

Abstract: In an implantable pacemaker the pacing rate is adjusted in synchrony with the respiration of the patient to thereby mimic respiratory sinus arrhythmia noted in healthy patients. Preferably, first a metabolic demand parameter pacing parameter is derived from a metabolic demand of the patient, such as minute volume, and then this parameter is adjusted using a respiration detector. The adjustment may be made dependent on the exercise level of the patient, his age and his physical fitness.

Abstract: An annunciator for an implantable medical device encapsulated within a casing comprises a magnetically permeable stationary ring member including an integral inwardly projecting peripheral flange having opposed sides on which electrically conductive coils are mounted. An oscillating member encompassed by the stationary ring member includes a planar magnet member having opposed surfaces of opposite polarity and planar pole pieces are mounted to the first and second surfaces, respectively, in a sandwich-like construction. The oscillating member is movable along a longitudinal axis between extreme positions whereat the first pole piece, then the second pole piece is proximate the ring flange. Cyclic energization of the electrically conductive coils generates a cyclically alternating magnetic field, which interacts with the magnetic field of the oscillating member causing its oscillation between the first and second extreme positions.

Abstract: A helical winding formed by a wound ribbon and having a length considerably exceeding its diameter, is adapted for implantation into a patient's body. Adjacent turns of the winding partially overlap each other and overlapping portions of the ribbon engage each other to limit the relative axial motion of adjacent turns. At least a portion of the overlapping structure is oriented non-parallel to the longitudinal axis of the winding. In a method of manufacturing such a winding a ribbon is formed to a desired cross-sectional shape with a longitudinally expanding engagement structure. The ribbon is then wound on a mandrel to produce a winding of desired length, with adjacent turns partially overlapping each other and the engagement structure causing overlapping portions of the ribbon to be mechanically engaged so as to limit the relative axial motion of adjacent turns of the winding. Finally the mandrel is removed out of the wound winding.

Abstract: A system for analyzing cardiac waveforms is provided that allows a physician to accurately measure specific portions of a displayed IEGM or EKG signal. By examining the cardiac waveform with the analyzing system, the physician can quickly and accurately determine whether the device is operating properly. The physician may use one or two cursors or an icon or pointer to define a specific portion of the cardiac waveform to be analyzed. Various waveform characteristics such as relative waveform amplitude, maximum slew rate, power spectral density, and time elapsed can be determined for the specific portion of the cardiac waveform. If desired, the waveform characteristic determined for the specific portion of the cardiac waveform can be compared to statistical waveform data (e.g., in the form of a histogram).

Abstract: A connector assembly mounted on an implantable cardiac stimulation device has an actuator mechanism for fixing and sealing electrical leads inserted into lead receptacles within the connector assembly without the use of setscrews. Fixing and sealing of the leads is accomplished by compressing resilient lead lock seals of O-ring shape, disposed in annular recesses, with lip portions of a plunger drawn toward the molded support by the actuator mechanism. In a first embodiment of the actuator mechanism, rotation of a cam actuator transversely journaled within the support, using a torque wrench or similar tool, moves a cam slide attached to the plunger through a fixed displacement between lock and unlock positions as an offset camming portion of the actuator engages the surfaces of a slot within the cam slide.