Abstract: A battery condition warning system for use in a battery powered medical implant device which generates an audible alarm to warn the patient of an impending battery failure. The warning system monitors the voltage potential of the battery during operation of the defibrillator, and when the voltage potential falls below a predetermined level, it activates an audible alarm which is heard by the patient. The system further includes a control circuit adaptable to deactivate the audible alarm in response to a first external magnetic condition, to deactivate the timer in response to a second external magnetic condition, or to conduct an internal test in response to a third external magnetic condition.

Abstract: The invention relates to an arrhythmia detection system and method for defibrillating the heart of a patient experiencing abnormal cardiac rhythm, wherein the abnormal cardiac rhythm (comprising one of fibrillation, high rate tachycardia, and low rate tachycardia) is first detected, the heart rate is sensed so as to distinguish between fibrillation and high rate tachycardia, on the one hand, and low rate tachycardia, on the other hand, and automatic defibrillation of the heart of the patient is implemented when one of fibrillation and high rate tachycardia is determined. In one embodiment, base and apical electrodes are connected to a probability density function (PDF) circuit and a rate circuit. When both abnormal cardiac rhythm and excessively high heart rate are detected, defibrillation of the heart of the patient is implemented.

Abstract: The invention relates to an apparatus for combining pacing and cardioverting functions in a single implanted device, circuitry being provided not only to interface the defibrillator to the ECG amplifier and other elements of the device, but also to provide protection of the ECG amplifier from the defibrillator output pulses, from loading by the defibrillator itself, and from overloading by externally generated defibrillator pulses. A specific embodiment of the invention combines a defibrillator, a pacer and an ECG amplifier in a single implanted device utilizing two terminal-electrode lead combinations for connection to the patient, while further embodiments employ three and four terminal-electrode lead combinations. The invention employs a high-frequency transformer coupling technique for pacing, or, alternatively, high-frequency transformer coupling with modulation-demodulation.

Abstract: An implantable heart stimulator and related method calls for the determination of a given heart condition from among a plurality of conditions, the selection of at least one mode of operation for treating the determined condition, and the execution of the mode of operation selected, so as to treat the determined condition. In one embodiment of the invention, wherein a plurality of modes of operation for treating the various conditions are provided, the implantable heart stimulator includes processors, each processor being designed to efficiently execute a respective group of modes of operation. A further embodiment of the present invention calls for the implantable heart stimulator to be implemented by at least one programmable microprocessor. A still further embodiment calls for the provision of a data input/output channel, by means of which data can be provided to and retrieved from the implantable heart stimulator.

Abstract: A heart rate detector apparatus, particularly for use in an implantable defibrillator, is disclosed. The heart rate detector apparatus includes two distinct detector circuits each responsive to ECG waveforms of different characteristics. One of the detector circuits is responsive to ECG waves having slew rates above a predetermined threshold. The other detector circuit is responsive to ECG waves having lower slew rates, such as ECG waves of more sinusoidal shape. A coupling circuit automatically couples one of the two detector circuits to an output circuit, such as a heart rate comparator. In a specific embodiment, the heart rate comparator determines the heart rate, compares the heart rate with a predetermined rate, and, if the heart rate exceeds the predetermined rate for a predetermined time period, provides an output signal. The output signal may be used to enable a defibrillating circuit to deliver a defibrillating shock to the patient.

Abstract: A fully implantable power supply for use with or in a fully implantable defibrillator, which has a fibrillation detector in circuit with the power supply and a power inverter switchably in circuit with the power supply. The power supply comprises an energy source which includes a plurality of batteries arranged in series, each of the batteries having a pair of output terminals, each of the batteries producing a multilevel voltage across its pair of output terminals, the voltage being at a first level when the battery is fully charged and dropping to a second level at some point during the discharge of the battery. Circuitry in the form of a plurality of unidirectional conducting devices is provided for creating a first conductive path between the serially-connected batteries and the fibrillation detector, and a second conductive path between the inverter and the batteries that are producing the first level of voltage.

Abstract: An externally controlled implantable electronic device for delivering a cardioverting pulse of energy to the atrium of an ailing heart. In one embodiment, the device is particularly suited for use when the patient visits the office of his physician, and contemplates the transmission of both information and powering energy through the skin of the patient. In another embodiment, the device can be readily operated at home, by the patient, and without the intervention of the physician. Here, the source of energy is permanently implanted.

Abstract: A specialized clip and method for electrically and mechanically joining a highly-flexible electrical conductor and a fine metallic mesh or screen for use in medical electrodes. The clip is in the form of an inverted U and has a portion of the wire mesh folded thereinto such that upon insertion of the flexible electrical conductors into the channel of the U-shaped clip containing the mesh the clip may be mechanically crimped to bring about intimate contact between the flexible conductors and the mesh. The mesh portion is then welded to the main body of the wire mesh and the wire mesh may then be subsequently used in the manufacture of implantable medical electrodes, for example, defibrillation electrodes.

Abstract: A method and apparatus for maximizing stroke volume through atrioventricular pacing using an implanted cardioverter/pacer accomplishes AV pacing with an AV delay tailored to the particular patient, thereby maximizing accuracy and efficiency. The invention involves the measurement of successive impedance changes, or swings, from one heart cycle to the next, across a pair of electrodes connected in proximity to the heart, the processing of the successive impedance changes to detect variations and directions of variations thereof, the issuance of atrial and ventricular pacing pulses, separated by a time interval therebetween, to the atria and to the ventricles, respectively, and the selective increasing or decreasing of the time interval between the atrial and ventricular pacing pulses in dependence on the directions of variation of the successive impedance changes to maximize impedance swings.

Abstract: A method and apparatus for effecting automatic ventricular defibrillation and/or demand cardioversion comprises an implanted automatic defibrillator having a normal (ventricular defibrillation) mode of operation and a cardioverting (demand cardioversion) mode of operation. One embodiment of the invention includes a simulated fibrillation source, externally located, for applying a simulated fibrillation signal to the patient via corresponding electrodes, the internal automatic defibrillator detecting the simulated fibrillation signal and responding thereto so as to apply a defibrillating voltage (in the normal mode) or a cardioverting voltage (in the cardioverting mode) to the heart of the patient. Another embodiment of the invention also includes an external command system, by means of which the implanted automatic defibrillator is actuated from the normal mode to the cardioverting mode, to reduce the discharge energy level, to cardiovert in synchronization with the QRS complex, or both.

Abstract: Disclosed is an implantable cardiac electrode for use in defibrillation. The electrode has a metallic mesh electrode surface surrounded by an insulating material which is formed so as to increase the metallic surface area while providing a substantially uniform current density across the electrode surface. An additional electrode tip is included for use in the event that pacing is required; the pacer tip may have a detachable lead for removal after surgery. The electrode may be implanted without major surgery by means of a specialized insertion tool which cooperates with a pocket formed in the electrode. After implantation, the electrode may also be used as a pick-up in an electrocardiogram system.

Abstract: A method for implanting an electrode adjacent the heart of a patient without requiring major surgery. A skin incision is made in the anterior thoracic region and/or in the abdominal wall, and by means of a specialized implantation tool tunnels are created through which the electrodes may be inserted and placed in contact with the heart. The implantation tool cooperates with the electrode such that after placement of the electrode the tool may be withdrawn from the patient with the electrode remaining in place.

Abstract: A fluid-tight electrical coupling for a medical device fully implantable in the body of a recipient, such as an implantable defibrillator, is disclosed. The fluid-tight coupling is mounted on a hermetically sealed casing. The coupling comprises a housing having receptacles for receiving an electrical conductor plug. Terminal blocks are provided within the housing and define a pin opening for receiving the pins of the electrical conductor plug. The terminal block is electrically connected to the exterior of the housing. The terminal block also includes a cylindrically shaped boss extending from a face of the terminal block. The boss is externally and internally threaded for receiving a sealing cap and a retaining member respectively. The retaining member comprises a hexagonal socket head set screw. The sealing cap seals off the interior of the housing. The sealing cap is secured to the terminal block to seal off the housing opening by means of a screwdriver that is adapted to retain the sealing cap thereto.

Abstract: A fully implantable defibrillator in which the components of the defibrillator are housed within an implantable casing. Defined within the implantable casing are two chambers. Each of the chambers is hermetically sealed from the other and from the exterior environment surrounding the implantable casing. Disposed within the first chamber is a battery and an energy storage device. A charging circuit is disposed within the second chamber and is operatively associated with the battery and the energy storage device for charging the energy storage device to a level capable of defibrillating a malfunctioning heart. A discharging circuit is disposed within the second chamber and is operatively associated with the energy storage device, for initiating the discharge of the energy storage device into the heart of the wearer. The geometry of the implantable casing is chosen to optimize the packaging of the defibrillator components therein.

Abstract: A device for recording and subsequently reproducing information, such as desired portions of an ECG signal produced by a heart prior to and during the occurrence of a disturbance in cardiac electrical activity. Two basic embodiments of the inventive recorder are contemplated. One embodiment is fully implantable and is encased with sensing and defibrillating electronics. With this embodiment, a low-power, low-capacity, continually updated recorder is continually operative, and a high-capacity stand-by recorder is actuated upon the sensing of fibrillation. An external device is used to retrieve by telemetry, the information stored in the implanted recorder. The second embodiment of the inventive recorder is an external device which has external electrodes for associating with the patient; ECG information is transmitted to the recorder unit by telemetry. Here, because power consumption is not so critical as with the implantable embodiment, a delay-type continually updated memory is continuously operative.

Abstract: Disclosed in an implantable cardioverter having the capability of communicating with its wearer. In one specific embodiment, the cardioverter is an automatic, fully implantable ventricular defibrillator including an electrical stimulator to deliver a mild shock to the wearer to inform the wearer, for example, that fibrillation has been sensed. In another embodiment, communication from the implanted defibrillator to the wearer is by means of an implanted audio transducer. And in a third embodiment the implanted defibrillator communicates with the wearer by issuing a mechanical vibration. Also disclosed is a mechanism whereby the wearer is able to disenable the defibrillator, and prevent the delivery of a defibrillating pulse.

Abstract: Disclosed is a method and an apparatus for monitoring heart activity, for indicating or detecting abnormalities in such activity, and for taking corrective measures to return an arrhythmic heart to normal sinus rhythm. In one embodiment, monitoring and detecting are accomplished by developing a probability density function from ECG signals, or by sampling at least two portions of a probability density function. In another embodiment, a phase lock loop circuit is utilized to indicate fibrillation by the loop's inability to lock onto R--R interval signals. And in still another embodiment, cardiac electrodes are used to sense pulsatile impedance changes, absent in the presence of fibrillation. Also disclosed is a two-stage detector whose second stage is brought out of a stand-by state only after an arrhythmic condition is indicated by the first stage.