Abstract: A method and apparatus for measuring battery depletion in an implantable medical device is presented. The apparatus includes first and second switch pairs disposed in series between the battery and a load, and connected in a parallel arrangement with respect to one another. A capacitor is connected in a first polarity between the battery and the load when only first and fourth switches are closed and in a second polarity when only second and third switches are closed. A comparator circuit causes the switches to reverse the capacitor's polarity based on a comparison of the voltage drop across the capacitor to a threshold value. A counter counts the number of times the capacitor reverses polarity, which is proportional to the amount of charge transferred from the battery during its lifetime in the device and indicative of the battery's level of depletion.

Abstract: A technique is provided for detecting episodes of cardiac ischemia based on an examination of the total energy of T-waves. Since cardiac ischemia is often a precursor to acute myocardial infarction (AMI) or ventricular fibrillation (VF), the technique thereby provides a method for predicting the possible onset of AMI or VF. Briefly, the technique integrates internal electrical cardiac signals occurring during T-waves and then compares the result against a running average. If the result exceeds the average by some predetermined amount, ischemia is thereby detected and a warning signal is provided to the patient. The maximum slope of the T-wave is also exploited. Techniques are also set forth herein for reliably detecting T-waves, which help prevent P-waves from being misinterpreted as T-waves on unipolar sensing channels. The T-wave detection technique may be used in conjunction with ischemia detection or for other purposes.

Abstract: Current usage from a battery in an implantable cardiac device is tracked. The apparatus includes a battery current sensor having multiple current ranges. The current sensor produces a first signal representative of current drawn from a battery. A current range selector selects a current range for the battery current sensor and produces a second signal representative of the current range. An accumulator accumulates the first signal based on the second signal over time to generate an output signal representing usage of the battery.

Abstract: An implantable cardiac stimulation device comprises a physiologic sensor and one or more pulse generators. The physiologic sensor is capable of sensing a physiologic parameter. The pulse generators can generate cardiac pacing pulses with a timing based on the physiologic parameter. The timed cardiac pacing pulses can prevent a sleep apnea condition. In one example, a cardiac stimulation device has a physiologic sensor and can be configured to pace a patient's heart according to a rest mode of operation. The cardiac stimulation device uses measurements from the physiologic sensor to prevent and treat sleep apnea using a revised rest mode of operation. The revised rest mode operates under a presumption that sleep apnea is primary to a reduced heart rate, rather than secondary, so that pacing at a rate higher than the natural cardiac rate during sleep will prevent sleep apnea.

Abstract: A medical electrical lead to conduct electrical stimulation and/or signals between an electrical stimulator and a heart site includes an elongated lead body extending to a proximal connector for attachment to the electrical stimulator. An electrode head at the distal end includes an electrode tip member for fixation to the heart and an electrode backing member fixed to the lead body is releasably attachable to the electrode tip member for transmission of electrical signals between the heart and the electrical stimulator. The electrode tip member may include a first non-conductive base with an outwardly projecting tip electrode and a first mounting member projecting oppositely away from the non-conductive base. The electrode backing member includes a second non-conductive base and a second mounting member thereon adapted for mounting engagement with the first mounting member for selectively releasably but firmly integrating the electrode tip member and the electrode backing member.

Abstract: An implantable cardiac device returns activations of corresponding right and left chambers of a heart to inter-chamber synchrony. A sensing circuit senses intracardiac signals representing right and left chamber ventricular electrical activity. A detector determines if a predetermined characteristic of the electrogram signals indicates dissociation of the corresponding right and left chambers. If dissociation is indicated, a pulse generator stimulates at least one of the corresponding chambers to restore inter-chamber synchrony.

Abstract: An implantable cardiac stimulation system delivers arrhythmia termination pulses to the ventricles and the atria of a heart. The system includes an implantable cardiac stimulation device, including a conductive enclosure, ventricular arrhythmia termination pulse generator, and an atrial arrhythmia termination pulse generator. A first electrode configuration, including the conductive enclosure, is arranged to be coupled to the ventricular pulse generator to terminate ventricular arrhythmias and a second electrode configuration, electrically independent from the conductive enclosure and confined within the heart, is arranged to be coupled to the atrial pulse generator to terminate atrial arrhythmias.

Abstract: An implantable lead for use with an implantable medical device includes a lead body with first and second electrical conductors extending between its proximal and distal ends. An electrical connector at the proximal end of the lead body includes terminals electrically connected to the first and second conductors. First and second coaxial active fixation helices are coupled to the lead body's distal end, one being an anode, the other an electrically isolated cathode. Each helix has an outer peripheral surface with alternating insulated and un-insulated portions along its length with about a half of the surface area being insulated. The un-insulated portions of the helices may be formed as a plurality of islands in the insulated portions, or as rings spaced by insulative rings, or as longitudinally extending strips spaced by longitudinally extending insulative strips.

Abstract: A high density electronic circuit for use in an implantable stimulation device that comprises a flexible substrate that has the advantage of integrating “chip-and-wire” microelectronic circuits and flexible interconnections that are adapted to conform to the body compatible housing into a single structure. The flexible substrate has die attach pads, each die attach pad having a set of wire bond pads therearound, each wire bond pad being connected to conductors formed within the substrate according to circuit function. A plurality of chip-and-wire integrated circuit (IC) chips are mounted by epoxy die attachment on the die attach pads, each IC chip has a plurality of contact pads formed on a top surface thereof, and gold wire bonds electrically connect the plurality of contact pads to the wire bonds pads. The wire bonds include a primary bond and, optionally, a safety bond for reinforcement. Other techniques are disclosed to enable the use of the gold wire bonds on a flexible substrate.

Abstract: A connector assembly for an implantable medical device including a casing includes a header having a receptacle with an electrical contact for engageably receiving an electrical terminal on a proximal end of a lead and a fastener assembly for simultaneously releasably clamping the lead to the header within the receptacle and firmly attaching the header to the casing. The header is mounted on the casing and has a distal notched region with an upper surface and a first channel in its upper surface aligned with, and being a partial extension of, the receptacle. The fastener assembly includes a lead-lock component engageably received within the notched region of the header and with a second channel therein which is aligned and juxtaposed with the first channel, the channels taken together being an extension of the receptacle. A fastener system firmly mounts the lead-lock component to the header at the notched region.

Abstract: An implantable cardiac stimulation device is configured to measure selected ventricular contraction parameters and possibly apply stimulation therapy based on the ventricular contraction parameters. In accordance with one aspect, the ventricular contraction parameters include impedance values that correspond to the volume of fluid in the right ventricle and the left ventricle. In accordance with another aspect, the ventricular contraction parameters include motion values that correspond to heart sounds/motion in the right ventricle and the left ventricle. The ventricular contraction parameters can be used to form pseudo P-V loop from which treatment decisions can be made.

Abstract: Techniques for enabling both preventive overdrive pacing and antitachycardia pacing (ATP) within an implantable device are provided. The device gains the benefits of overdrive pacing for preventing the onset of a tachycardia and, if one nevertheless occurs, ATP is employed to terminate the tachycardia. In particular, a technique is provided for promptly detecting the onset of atrial tachycardia during preventive overdrive pacing based on loss of capture of atrial pacing pulses. A technique is also provided for using detection of loss of capture of atrial or ventricular pacing pulses to trigger automatic switching from overdrive pacing to ATP. A setup technique determines whether to enable the automatic switching from overdrive pacing to ATP within a particular patient. Also, techniques are provided for verifying loss of capture of atrial or ventricular backup pacing pulses and for detecting low amplitude ventricular fibrillation based on loss of capture of ventricular backup pacing pulses.

Abstract: Techniques are provided for detecting the circadian state of a patient using an implantable medical device based on selected blood carbon dioxide (CO2) parameters. In one example, the implantable device tracks changes in end tidal CO2 (etCO2) levels and changes in maximum variations of pCO2 levels per breathing cycle (?cycleCO2) over the course of the day and determines the circadian state based thereon. It has been found that average etCO2 levels are generally highest and average ?cycleCO2 levels are generally lowest while a patient is asleep and opposite while a patient is awake. Hence, by tracking changes in average etCO2 and ?cycleCO2 levels over the course of the day, circadian states can be detected. Minute ventilation and activity levels are used to assist in the determination of the circadian state. Additional techniques are directed to detecting the stage of sleep.

Abstract: A signal indicative of cardiac contractions of a patient's heart is produced, as the patient's heart is paced using different sets of pacing interval parameters. Measures of pulse amplitude are obtained from the signal. Pacing interval optimization is performed based on the measures of pulse amplitude.

Abstract: The prophylactic pacer/defibrillator is configured to deliver shocking therapy in response to a single episode of ventricular fibrillation, as well as delivering otherwise conventional pacing therapy. By providing “one shot” defibrillation capabilities a patient who is not at significant risk of ventricular fibrillation—and hence is not a candidate for a full-service implantable cardioverter defibrillator (ICD)—can receive defibrillation therapy in the event ventricular fibrillation should nevertheless occur. Once the prophylactic pacer/defibrillator has delivered shocks to terminate the single episode of ventricular fibrillation, the patient returns to his or her physician to have the device removed and a full-service ICD implanted, so that any additional episodes of ventricular fibrillation may be addressed by the full-service ICD.

Abstract: The prophylactic pacer/defibrillator is configured to deliver shocking therapy in response to a single episode of ventricular fibrillation, as well as delivering otherwise conventional pacing therapy. By providing “one shot” defibrillation capabilities a patient who is not at significant risk of ventricular fibrillation—and hence is not a candidate for a full-service implantable cardioverter defibrillator (ICD)—can receive defibrillation therapy in the event ventricular fibrillation should nevertheless occur. Once the prophylactic pacer/defibrillator has delivered shocks to terminate the single episode of ventricular fibrillation, the patient returns to his or her physician to have the device removed and a full-service ICD implanted, so that any additional episodes of ventricular fibrillation may be addressed by the full-service ICD.

Abstract: An implantable cardiac system has a master pacing unit and a remote satellite pacing unit. The master pacing unit is electrically coupled to a right side of a patient's heart via a lead assembly. The satellite pacing unit is a leadless device mounted on the left side of the patient's heart and is wirelessly controlled by the master pacing unit. The satellite pacing unit is affixed to the heart by one or more mounting members. The base of the satellite unit case has a gel-like material which facilitates adhesion of the pacing unit to the heart tissue. The gel-like material promotes tissue growth to hold the pacing unit in place on the heart. The gel-like material may be composed of polyvinlpyrrolidone and may contain a steroid, such as dimethyl sulfoxide (DMSO), or dexamethazone sodium phosphate.

Abstract: An implantable cardiac device having an impedance monitor has an impedance monitoring control. The impedance monitor includes a pulse generator that applies a current between a pair of implanted electrodes and an impedance measuring circuit that measures impedance across the implanted electrodes and provides an impedance signal during a present time that the pulse generator applies the current between the pair of implanted electrodes. The impedance monitoring control processes the impedance signal to provide impedance monitoring characteristic results and compares the results to preset standards. A control circuit varies the operating parameters of the impedance monitor responsive to the comparison of the impedance monitoring characteristic results to the present standards.

Abstract: This invention relates generally to apparatus and methods for the calibration of implanted pressure transducers. It is an object of several embodiments of the present invention to provide apparatus and methods for the calibration of one or more implanted pressure transducers implanted in the body of medical patients. Various embodiments of the present invention are particularly advantageous because they offer a calibration system that is less invasive than the systems currently available.

Abstract: According the present invention, anode foils are encapsulated in separator material so as to insulate them from the metal housing of an electrolytic capacitor. The present invention also provides for enclosed capacitor configurations for use in stacked capacitor configurations. Preferably, heat-sealable polymeric materials are used as separator materials to encapsulate or enclose the anode assemblies and capacitor configurations. The encapsulated anode assemblies and capacitor configurations of the present invention may be used in implantable cardioverter defibrillators.