Abstract: In a power supply circuit supplying a high voltage charger of an implantable cardioverter-defibrillator (ICD), a changer circuit switches the power source of the power supply circuit between a battery and an output signal of a step-up converter. The signal derived from the boost winding rises to a high voltage when the high voltage charger charges the storage capacitors of the ICD. A system current measurement circuit can be provided in the power supply circuit.

Abstract: An annunciator is provided for an organ stimulating system which is implantable in the body of a patient. A tubular support member is mounted at one end on the casing for the organ stimulating system and extends to a free end and an electrically conductive coil encircles the support member. An elongated oscillating member includes a field return member of magnetically permeable material which is spaced from and generally encircles the support member. The field return member extends between an integral head member at a proximal end generally proximate the free end of the support member and a distal end generally proximate the casing. A stack member is mounted on the head member and extends away therefrom toward the casing for the organ stimulating system.

Abstract: Improved methods of determining the recommended replacement time (RRT), and therefore extending the longevity, of implantable electronic medical devices, especially implantable cardioverter-defibrillators, pacemakers and similar devices, which rely on a battery having at least a minimal charge in order for the device to perform its intended function and devices employing these methods are described. In one embodiment, the improved method entails independent measurement of at least two different indicators of battery strength, at least one of which is affected by the battery's internal impedance. In a preferred embodiment, terminal battery voltage and capacitor charge time are independently monitored. If the terminal battery voltage falls below a predetermined minimum threshold or the capacitor charge time is confirmed to exceed a predetermined maximum charge time, an RRT signal is issued.

Abstract: A cardiac stimulation device having a reduced volumetric configuration contains a pair of high-voltage cylindrical discharge capacitors positioned at rounded edges within a device container. The capacitors have electrical contact tabs at one end which are inserted directly through apertures formed within an associated electronic module. The capacitor tabs are connected directly to the electronic module eliminating the need for secondary connectors or point to point wiring, thus reducing the number of connections. Direct connection of the capacitors to the electronic module allows for optimal positioning of the module within the container. Specifically, the generally planar module is oriented perpendicular to planar cover surfaces of the container. Irregularly shaped components attached to the surface of the module advantageously extend away from the surface into remaining voids within the container.

Abstract: A dual-chamber implantable pacemaker automatically sets its AV or PV interval to a value that is a function of the measured natural conduction time, or AR interval, of a user of the pacemaker. The AR interval is determined on a regular basis, thereby permitting the AV or PV interval set by the pacemaker to adaptively change with any changes in the AR interval. The AV or PV interval is set to a value that is a prescribed amount .DELTA. less than or greater than the measured AR interval. The measured AR interval is typically averaged, or otherwise determined or estimated, based on measurements of several cardiac cycles.

Abstract: In a method and apparatus for physiological signal processing, a number of measured physiological signals are obtained in vivo from a subject and at least one of these measured physiological signals is supplied to the input of each first signal processing unit in a group of first signal processing units. Within each signal processing unit, the physiological measurement signal (or signals) supplied thereto is/are subjected to at least one transfer function so as to produce a pre-treated signal at the output of that first signal processing unit. The pre-treated signals from all of the first signal processing units are combined in a second signal processing unit so as to produce at least one synthesized ECG signal.

Abstract: A protective device includes a cap member extending between a nose end having a chamber therein for freely receiving the distal electrode of an implantable medical lead having a plurality of outward angularly extending tines and a tail end and an integral conical shield defining a cavity at least partially protectively enveloping the tines. Retention members releasably attach the cap member to the distal electrode so as to inhibit its unintended removal and include a plurality of resilient elongated fingers of a silicone elastomer at the tail end equal in number to the tines at circumferentially spaced locations about a longitudinal axis of the device. Each adjacent pair of fingers is constructed so as the snappingly receive and capture the tine in engagement therewith such that removal of the tine from the retention recess by movement of the cap member in the opposite direction is positively inhibited by the transverse edges.

Abstract: A method for storing digitized electrogram and diagnostic data in a read/write memory of an implantable cardiac therapy device which includes the steps of configuring the memory into first and second memory blocks, configuring the first memory block into a plurality of successive EGM data records for storage of the electrogram data, and the second memory block into a plurality of successive diagnostic data records for storage of the diagnostic data, storing successive electrogram data corresponding to successive EGM trigger events in respective, successive ones of the EGM data records, and, storing successive diagnostic data corresponding to successive diagnostic trigger events in respective, successive ones of the diagnostic data records. The electrogram data is preferably written into the EGM data records in a wraparound, FIFO manner.

Abstract: An implantable cardiac pacemaker is provided for delivering pacing pulses to a patient, where the pacing pulses are defined by at least two parameters. The pacemaker allows for transitioning of the two parameters from first values to second values in response to the patient's circadian rhythms, such as in response to the beginning and ending of a sleep cycle. Also provided is an implantable pacemaker for delivering pacing pulses to a patient where the pacing pulses are defined by at least one parameter. The pacemaker allows for selective transitioning of the parameter from a first value to a second value in response to the patient's circadian rhythms.

Abstract: A method for detecting cardiac arrhythmias which includes the steps of detecting a patient's cardiac activity, counting the number of intervals which satisfy a first selected criterion, and producing a sinus interval history count indicative of the number of such intervals which are counted, making a preliminary diagnosis of tachyarrhythmia upon detecting that the cardiac activity satisfies a second selected criterion, and, making a final diagnosis of tachyarrhythmia if the sinus interval history count is less than a selected maximum sinus interval history count, and otherwise, inhibiting a final diagnosis of tachyarrhythmia.

Abstract: An electrical connector assembly is provided for detachably coupling an electrical lead to a medical device. A hollow barrel has a through passage which extends between proximal and distal ends. A leaf spring member includes a base element on the barrel adjacent the distal end and a plurality of integral resilient spring elements extend away from the distal end at a plurality of circumferentially spaced locations to tip ends adjacent the proximal end. The leaf spring elements have contact portions intermediate the base element and the tip ends projecting and biased toward a longitudinal axis of the barrel for mating engagement with a proximal end of the electrical lead when inserted into the barrel from the distal end. A guide device on the barrel adjacent the proximal end and overlying the tip ends of the resilient spring elements serves to guide the electrical lead past the tip ends of the resilient spring elements without engaging the tip ends both during insertion and extraction.

Abstract: An implantable medical device for in vivo electrochemical measurements of blood properties, such as measurements of, inter alia, oxygen pressure, glucose and pH, avoids the problem with the reference electrodes currently in use which cause inflammatory reactions of tissue, by forming the reference electrode of carbon, preferably activated pyrolytic carbon.

Abstract: A stylet unit suitable for stiffening a hollow electrode cable, such as during the introduction and the anchoring of a medical electrode cable in the human body, includes a combination of a pair of flexible, coaxially arranged stylet elements, i.e., a tubular stylet sleeve and an internal stylet, which can be inserted into a channel in the sleeve and whose end section is pre-bent to one side. Both the stylet sleeve channel and moving inner stylet contained therein have sections or segments with non-circular cross-sections, the profile of the stylet's non-circular cross-section, in relation to the profile of the sleeve channel's non-circular cross-section, preventing the stylet from rotating in relation to the surrounding sleeve, at least within the parts of the sleeve in which both the stylet and the sleeve channel have interacting non-circular cross-sections.

Abstract: An apparatus and a method for an improved user interface for communicating with implantable medical devices are described. An integrated digitizer display screen and a digitizer pen serve as the primary input devices to a tablet computer adapted to receive real-time and stored medical data. The pen is used to select programming options by tapping portions of the digitizer based on visual images on the display. Additionally, the pen may be used to manipulate the medical data through the use of gestures, or be used to enter free form annotations concerning the medical data. An additional aspect of the user interface is the use of a questionnaire card to input information into the tablet computer by tapping the pen on the marked answers on the questionnaire card.

Abstract: An implantable defibrillator has an electrode lead system a sensing unit for sensing the condition of the heart and emitting a condition signal corresponding to that condition, a control unit for determining the heart's condition from the condition signal and, if a state of fibrillation is present, sending a command signal to a shock pulse generator, which, depending on the command signal, delivers at least one defibrillation shock to the heart via the electrode lead system. The shock being formal of one or more low-energy pulses with an energy less than 2 Joules and a very high voltage, i.e. more than 1,000 Volts. Each low-energy pulse thus has a voltage greatly exceeding the voltage in a conventional defibrillation shock and less energy than the energy in a conventional defibrillation shock.

Abstract: A system and method for acquiring medical data, integrating recently acquired medical data with previously acquired medical data, storing the integrated medical data, and displaying the integrated medical data to a medical practitioner in a convenient format appropriate for the type of data stored are provided. Recently acquired medical data are integrated with historical medical data in an implantable medical device programmer. The data may be initially displayed in graphical and text formats during a patient's follow-up visits. The historical medical data may be stored in the programmer, in the implantable medical device or both. Medical data may include physiologic data pertaining to the patient's medical condition, parametric data pertaining to the operational characteristics of the implantable medical device, identification data, including patient's background information, and comments including the medical practitioner's comments.

Abstract: A high voltage charger operates in a three-phase cycle. In a first phase, the high voltage charger operates at a fixed frequency. In a second phase, the high voltage charger operates at a variable frequency designed to draw a substantially constant average current from a power source. In the third phase, the high voltage charger returns to fixed frequency operation. The variable frequency is the reciprocal of the sum of an on-time and an off-time of the switch. In one embodiment, the on-time is provided by the time required for the switch to reach a predetermined maximum and the off-time is provided by the time over which a magnetic field in a transformer collapses.

Abstract: A stylet unit, which can be introduced into a hollow, flexible component, such as an electrode cable, to stiffen the component and to bend a distal end section is formed by a double stylet combination of a flexible tubular stylet shell and an internal stylet, movably arranged inside the shell's channel, with a pre-curved distal end section. This end section can be set at a retracted internal position inside the stylet shell or at an exposed position outside the shell. The internal stylet's pre-curved distal end section is made of a memory metal and has a radius of curvature which varies longitudinally along the end section. The end section can be in the shape of a spiral, and the memory metal can be made of a nickel-titanium alloy.