Abstract: There is provided a system and method of rate responsive pacing, having an intrinsic QT rate sensor. The system has the capability of sensing the QT interval of intrinsic cardiac signals and constructing from such intrinsic QT data a QT reference curve. The QT reference curve is used for comparison with beat-to-beat QT interval data, in order to provide sensor information for controlling pacing rate. The system of this invention preferably utilizes DSP circuitry for determining the occurrence of a Twave event and the timing of the Twave, from which the QT interval is calculated. The system also provides for compensation of any QT interval which is calculated following ventricular pacing, so that the QT sensor is operative at all times and throughout the entire rate range experienced by the patient. The system thereby provides an enhanced QT rate responsive pacing arrangement, and avoids the need of overdrive pacing in order to obtain QT reference data.

Abstract: An implantable medical device includes a sensor and a T-wave analyzer. The sensor is implantable within the body of a patient to sense electrical cardiac activity and provide an indication of T-wave alternans within the heart of the patient. The T-wave analyzer is responsive to the sensor, and evaluates cardiac risk based on comparison of the indication of T-wave alternans to a predetermined criterion. The T-wave analyzer may form part of a microprocessor, a digital signal processor, or combination of both. The device may include a pacing generator that applies increased rate pacing stimuli to the heart to facilitate sensing of the T-wave alternans by the sensor. The device also may incorporate a memory that stores the T-wave alternans indication provided by the sensor, e.g., over a number of heartbeats. In addition, the device may be equipped to provide an alert to the patient or a physician in the event the processor generates the indication of cardiac risk.

Abstract: An improved system and method for detecting dislodgement of an implantable medical device (IMD) such as a catheter or lead is disclosed. The system includes means for generating multiple, orthogonally-related signals within a body. For example, three current signals having a current path substantially oriented in the X, Y, and Z directions may be generated within the body. The invention further includes an IMD having an affixation device such as a helix at a distal tip for attachment to body tissue, and at least two sensing devices to sense the signals generated within the body. The difference in signal levels between two of the sensing devices may be measured. For example, a voltage potential difference created by the currents within the body may be measured between two electrodes. This measured signal level has components in the X, Y, and Z directions, and may therefore be used to define a directional vector in three-dimensional space. This vector is indicative of the orientation of the IMD.

Abstract: A medical information communication system and corresponding methods are described. The system permits monitoring the performance of an implantable medical device (IMD) implanted within a body of a patient, monitoring the health of the patient, or remotely delivering a therapy to the patient through the IMD. The IMD is capable of bi-directional communication with a communication module, a mobile telephone and/or a Personal Data Assistant (PDA) located outside the patient's body. The system may comprise the IMD, the communication module and/or a mobile telephone and/or a PDA, a remote computer system, and a communication system capable of bi-directional communication, where the communication module, the mobile telephone and/or the PDA are capable of receiving information from the IMD or relaying information thereto.

Abstract: Flat electrolytic capacitors, particularly, for use in implantable medical devices (IMDs), and the methods of fabrication of same are disclosed. The capacitors are formed with an electrode stack assembly comprising a plurality of stacked capacitor layers each comprising an anode sub-assembly of at least one anode layer, a cathode layer and separator layers wherein the anode and cathode layers have differing dimensions that avoid electrical short circuits between peripheral edges of adjacent anode and cathode layers but maximize anode electrode surface area.

Abstract: Myocardial performance is assessed using a combination of electrical and mechanical criteria. More specifically, this assessment may be based on a QT interval based on electrogram (EGM) readings and on first and second heart sounds. The timing relationships between the QT interval and the first and second heart sounds can be used to evaluate certain systolic, diastolic, and systolic/diastolic parameters relating to myocardial performance. In addition, these parameters may be used to automatically drive therapies. For example, myocardial performance parameters obtained from the QT interval and from the timing of the first and second heart sounds may be used to optimize the AV delay and to optimize multisite pacing.

Abstract: An implantable medical device substrate is free form cut to the shape of the interior of the device. The free form shape allows more efficient use of not only the interior space of the device but also of the substrate itself. Integrated circuit components are formed to fit the shape of the substrate, freeing areas in the device for additional components, or allowing the device to be made smaller through a maximized use of the available space-volume.

Abstract: A method for forming a stackable wafer for use in an implantable device is provided. The method comprises forming an opening extending substantially through the wafer. Thereafter, conductive material is deposited within the opening to substantially fill the opening. A bump is then formed on an upper surface of the wafer adjacent the conductive material, and a contact pad is formed on a lower surface of the wafer adjacent the conductive material. A second wafer formed using substantially the same process may then be stacked on top of the first wafer with the bump of the first wafer being in contact with the contact pad of the second wafer. A soldering process may then be used to couple the adjacent pad and wafer for physically mounting the wafers and providing electrical connectivity therebetween.

Abstract: An ADI/R mode is implemented using an intelligent pacing system to continually monitor ventricular response. This ensures AV conduction whenever possible so as to gain all the benefits of cardiac contractile properties resulting from native R-waves. In the event where AV conduction is blocked, the pacing mode is switched to a DDD/R mode to ensure a paced R-wave. Thereafter, subsequent to a completed interval of a p-wave, ADI/R pacing resumes to monitor ventricular response.

Abstract: A bi-furcated medical electrical lead that is adapted to be implanted in the cardiac venous system is disclosed. The lead includes a bifurcated distal portion having first and second elongated members, or fingers. In one embodiment, the first elongated member, or thumb portion, is adapted to be positioned within the coronary sinus or great cardiac vein. The second elongated member, or finger portion, of the bifurcated distal tip, may be positioned within a branch vessel of the coronary sinus such as the posterior vein or middle cardiac vein. The thumb portion may carry at least one electrode for pacing and/or sensing, and may carry additional electrodes for multi-polar pacing applications, whereas the finger portion may carry a defibrillation electrode. Portions of the pacing/sensing electrodes may be insulated so that electrical stimulation is only delivered to myocardial tissue.

Abstract: Methods and systems for monitoring the condition of a septum in an implantable medical device are disclosed. Monitoring of the septum provides the ability to determine whether a needle has pierced the septum to effect the transfer of fluids into or out of a reservoir in the implantable medical device. Septum monitoring may provide the ability to determine whether the septum is maintaining its ability to seal the reservoir against leakage. The systems of the present invention include an ultrasonic transducer acoustically coupled to the septum to emit ultrasonic energy directly into the septum. Insertion of a needle through the septum can be detected by the acoustical changes caused by the needle located within the septum.

Abstract: In general, the invention is directed to an implantable medical device assembly having a more space-efficient housing and components, as well as processes for assembling the implantable medical device with reduced assembly cost and less complexity. The implantable medical device may incorporate a battery, capacitor, circuit assembly, feedthrough assembly, and interconnect assembly with respective electrical terminals. This configuration permits the use of automated electronic module assembly techniques such as parallel gap or ribbon bond welding to electrically connect the terminals. A feedthrough assembly may present a set of terminals adjacent a corresponding set of circuit terminals, also enabling the use of automated welding techniques.

Abstract: An improved system for monitoring the status of an IMD such as a medical electrical lead during an implant procedure is provided. The system includes a signal generator for supplying a first signal such as a constant current or voltage to the IMD. A resulting voltage or current signal is generated, respectively, and may be sensed as an indication of the impedance of a portion of the body that is proximal to one or more electrodes carried by the lead. This impedance indication is converted to an audible signal having a frequency that is proportional to the amplitude of the impedance indication. The pitch of the audible signal therefore rises when measured impedance increases, and drops as the impedance decreases. These pitch changes allow a user to determine positional information associated with the IMD, including the degree of lead tissue contact and extent of fixation of a device to tissue.

Abstract: A medical device communications system uses subthreshold pulses, modulated to provide relatively high speed electrical communications with inexpensive external devices connectable to a body with the implant by surface leads.

Abstract: Methods are provided for forming a die package. The method comprises stiffening a flexible substrate to provide a first flexibility of the flexible substrate, forming a mounting element on a first side of the flexible substrate, and mounting a first die on the first side of the flexible substrate to couple the first die to the mounting element. Further, the method comprises mounting a second die on a second side of the flexible substrate and mounting a third die on the second side of the flexible substrate to couple the second and third die to the mounting element, respectively. Furthermore, the method comprises adjusting the stiffening to provide a second flexibility of the flexible substrate that is greater than the first flexibility, and stacking the second die and the third die to provide an overlap of a portion of the second die and a portion of the third die.

Abstract: Uplink and downlink telemetry between an implantable medical device (IMD) telemetry transceiver and an external medical device (EMD) telemetry transceiver used by a patient or health care provider is facilitated by the communications system of the present invention. The IMD provides a therapy and/or measures physiologic conditions of the patient for use in formulating a therapy and/or for storage in IMD memory for later uplink telemetry transmission. The patient causes the EMD to emit encoded dual tone multiple frequency (DTMF) tones that are detected by an audio receiver of the IMD to enable uplink and downlink telemetry transmissions in a telemetry or communication session. Then, the patient formulates a message via a message entry mechanism of the EMD that communicates an instruction or query to the IMD. The downlink message is optionally displayed by an EMD display as it is composed by the user and is then downlink telemetered to the IMD.

Abstract: An implantable medical device comprising a housing, a capacitor assembly, an electronics module and an energy source, such as a battery. The capacitor assembly is disposed within the housing. The electronics module is electrically connected to the capacitor assembly and similarly disposed within the housing. The capacitor assembly comprising a case, an electrode stack and an insulative liner between the case and the electrode stack. The capacitor assembly electrode stack comprising a plurality of electrode subassemblies each having a plurality of anode plates and a plurality of cathode plates with a separation layer between anode and cathode plates. The liner also maintains alignment and immobilizes the electrode stack within the capacitor assembly. Finally, the energy source is electrically connected to the electronics module. With this configuration, an overall shape and size of the implantable medical device is optimized.

Abstract: The current invention provides an improved system for monitoring status of an IMD within a body. The system includes a device such as a lead, guidewire, stylet, catheter, or other IMD carrying a device such as a microphone for detecting acoustic signals in the body. The IMD is coupled to an amplifier device which generates an audible signal that may be utilized to determine status associated with the IMD, including location and tissue-contact data. A processing circuit may further be provided to aid in the analysis of the acoustic data.

Abstract: A circuit for providing phase shifted I and Q output signals from a received FSK modulated signal and the method of its operation. The circuit includes apparatus for receiving an FSK modulated signal, first, second and third mixers, to which the received FSK modulated signal is applied, a local oscillator, generating an oscillator signal and phase shifters providing first, second and third phase shifted versions of the oscillator signal to the first, second and third mixers to produce first, second and third mixer output signals which are likewise phase shifted. The mixer output signals are provided to summing circuits providing an I output signal corresponding to the difference between the first and second mixer output signals a Q output signal corresponding to the difference between the second and third mixer output signals.

Abstract: Methods are provided for forming a die package. The method comprises stiffening a flexible substrate to provide a first flexibility of the flexible substrate, forming a mounting element on a first side of the flexible substrate, and mounting a first side of a die on a second side of the flexible substrate. In addition, the method comprises adjusting the stiffening to provide a second flexibility of the flexible substrate that is greater than the first flexibility, and positioning the flexible substrate to couple a contact of the flexible substrate with a second side of the die.