Abstract: An implantable pacemaker continuously records pacing events and their respective rates of occurrence in sequence, as they occur, into an Event Record stored in a circular buffer. The circular buffer always contains the most recent events and rates collected. The recording of the pacing events selectively occurs at every event, or at sampling rates of one event per fixed sample interval. A programming device, coupled to the implantable pacemaker through a telemetry link, selectively retrieves the recorded pacing events and rates from the Event Record and reports subsets thereof in condensed or summarized form using numerical and/or graphical formats. The pacing event data collected in the Event Record is three-dimensional in that each pacing event includes a pacemaker event, an associated pacemaker or heart rate, and a real time interval. The programming device also calculates and reports statistical information from the data collected in the Event Record.

Abstract: A programmable offset is added to an automatically generated baseline reference value to provide a Threshold value used by the rate-responsive sensor processing circuits of an implantable rate-responsive pacemaker to determine the significance of a sensor input signal. The rate-responsive pacemaker provides stimulation pulses on demand at a pacing rate determined by a sensed physiological parameter. The physiological parameter is sensed by a physiological sensor included within, or coupled to, the rate-responsive pacemaker. The physiological sensor generates a sensor input signal having a magnitude that varies as a function of the sensed physiological parameter. The invention provides a way for the rate-responsive pacemaker, when operating in an autothreshold mode, to automatically determine when the magnitude of the sensor input signal is sufficiently large to justify an increase in the pacing rate.

Abstract: A programmable output connector of an implantable cardioverter-defibrillator (ICD), or similar implantable medical device, allows each of a multiplicity of output terminals to be selectively connected to either a positive or a negative output bus of the ICD. The positive and negative output buses of the ICD, in turn, are switched to an output capacitor, or equivalent output circuit, of the ICD. An electrical charge stored on the output capacitor, or otherwise generated by the output circuit, is presented to the multiplicity of output terminals in accordance with a programmed polarity. The programmed polarity causes a selected one or group of the multiplicity of output terminals to be connected to the positive output bus, and a selected other or group of the multiplicity of output terminals to be connected to the negative output bus. Respective electrodes designed for contacting cardiac tissue may then be electrically connected to each one of the multiplicity of output terminals.

Abstract: A rate-responsive pacemaker (10) generates stimulation pulses on demand at a rate determined by a sensor indicated rate (SIR) signal. The pacemaker includes, in a preferred embodiment, an activity sensor (26) that generates a raw sensor signal (27) as a function of sensed body motion. The raw sensor signal is processed by two parallel signal processing channels with each channel emphasizing a different aspect of the raw sensor signal. A first sensor processing channel (28) produces a first processed sensor signal (S.sub.A) that is more sensitive to arm motion than to pedal impacts. A second sensor processing channel (30) produces a second processed sensor signal (S.sub.B) that is more sensitive to pedal impacts than to arm motion. The first and second processed sensor signals are each weighted by a programmable amount, and are then combined to form the SIR signal.

Abstract: Apparatus located in an implantable medication infusion pump for quickly and easily detecting a condition adversely affecting medication delivery in the implantable medication infusion pump is disclosed which can reliably detect occurrences including an occluded catheter, the presence of air in the pumping mechanism, and the failure of the pumping mechanism. The system uses the amplitude of an acoustic signal generated by operation of the pumping mechanism as compared with a baseline signal to detect an encapsulated or occluded catheter or air in the fluid line. In addition, the system can detect a partially encapsulated or occluded catheter by detecting repeated downward slope patterns during repetitive, closely spaced pumping cycles.

Abstract: A lead for delivering electrical stimulation pulses to pace the cardiac muscle and for sensing electrical signals occurring in the cardiac muscle is disclosed which as a rigid helix disposed at the extreme distal end thereof which rigid helix may be operated by the implanting physical to extend the tip of the rigid helix from a stored position within the distal end of the lead to a deployed position projecting from the distal end of the lead. The rigid helix pierces and engages the heart tissue to anchor the lead in place within the heart. The tip of the rigid helix has an axial bore therein which is filled with a therapeutic medication such as a steroid or steroid-based drug for inhibiting inflammation and promoting tissue growth. After the tip of the helical screw is disposed in the heart tissue, the therapeutic medication will be slowly eluted into the surrounding tissue, thereby minimizing the trauma of implantation and assisting in the anchoring of the lead.

Abstract: An implantable cardioverter-defibrillator (ICD) provides a tiered therapy designed to automatically terminate tachyarrhythmias using the least aggressive therapy possible while reducing the "time-to-therapy." The tiered therapy first applies a first tier of therapy (e.g., antitachycardia). If unsuccessful, the tiered therapy next applies a second tier of therapy (e.g., cardioversion pulse with a pulse of moderate energy). If unsuccessful, the tiered therapy finally applies a third tier of therapy (e.g., a high energy pulse). So that more aggressive (higher energy) tiered therapies may be applied as early as possible following the failure of a less aggressive (lower energy) therapy, the ICD begins charging one or more high voltage capacitors of the ICD in parallel with the application of the less aggressive therapy, and/or in parallel with the verification interval immediately following a prior therapy attempt during which the ICD attempts to verify the successful termination of the tachyarrhythmia.

Abstract: A pacing lead having a porous electrode of platinum-iridium with recessed areas or grooves formed into the surface. The grooves allow for acute electrode stabilization as a result of clot formation and endocardial tissue capture during insertion and immediate immobilization upon implant. At least one layer of a porous coating of 20-200 micron diameter spherical particles are deposited on the surface of the base electrode to obtain a porous macrostructure for promoting chronic tissue ingrowth. Additionally, a microstructure surface coating is applied to increase the active surface area and enhance electrical efficiency by lowering electrochemical polarization and increasing electrical capacitance.

Abstract: A method and system for monitoring the behavior of an implanted pacemaker counts (records) the number of times that a given internal event or state change of the pacemaker occurs, and also determines the rate at which each event or state change thus counted occurs. The event counts and their associated rate are stored (recorded) in appropriate memory circuits housed within the pacemaker device. At an appropriate time, the stored event count and rate data are downloaded to an external programming device. The external programming device processes the event count and rate data, and displays a distribution of the event count data as a function of its rate of occurrence, as well as other statistical information derived therefrom. The displayed information, and its associated statistical information, allows a baseline recording to be made that establishes the implanted pacemaker's behavior for a given patient under known conditions.

Abstract: A rate-responsive pacing system and method allows the inter-related sensor operating parameters associated with the physiological sensor of a rate-responsive pacemaker to be automatically and/or optimally set for a particular patient. The system includes both a pacemaker and an external programming device. The pacemaker includes appropriate memory circuits for recording a sensor indicated rate (SIR) signal in a histogram. The external programming device retrieves the SIR histogram data, as well as other data associated with the operation of the pacemaker, and selectively processes and displays such data in a prescribed manner. An Auto-Set sequence or routine, carried out by the external programming device, sets all of the rate-responsive operating parameters to a known initial value and places the pacemaker in a passive mode. In the passive mode the SIR signal does not control the pacing rate. The Auto-Set routine then displays instructions for the physician that cause diagnostic data to be collected.

Abstract: A physiological sensor forms an integral part of an implantable stimulation/sensing lead used with a medical device, such as a pacemaker. The stimulation/sensing lead includes a tip electrode to which a distal end of a first conductor is connected. The sensor is inserted in series with respective portions of a second conductor. A distal end of the second conductor/sensor is connected to the tip electrode. Operation of the stimulation/sensing lead occurs unipolarly through the first conductor only, with a signal return path being provided through the tip electrode and conductive body fluids. The sensor does not form part of the electrical circuit to the tip electrode, and there are no electrical connections or breaks in the insulation along the entire length of the first conductor.

Abstract: A telemetry system which will transmit data at a relatively high rate while retaining a high degree of accuracy is disclosed which utilizes a servo feedback loop in conjunction with a conventional reflected impedance receiving front end parallel LC circuit, an AM demodulator, and an oscillator to drive the LC circuit at a desired frequency. The feedback loop operates to keep the voltage across the LC circuit constant over time, and does not affect short term variations in the voltage across the LC circuit which are caused by the variations in the reflected impedance. While frequency response of the system without the loop declines from a maximum value at zero frequency, the frequency response of the system of the present invention with the loop is shifted which permits data transmission at a substantially higher rate.

Abstract: A method is provided for reconditioning a medication infusion pump by removal of accumulated medication deposits and the like to restore pump performance without requiring surgical removal of an implanted pump from a patient. The reconditioning process comprises sequential delivery of a buffer solution and a rinse solution to internal pump flow passages. The rinse solution is effective to dissolve medication deposits and the like within narrow pump flow passages before the rinse solution is neutralized by intermixing with the buffer solution. Dissolution of accumulated medication deposits results in restoration of pump performance substantially to original product specifications.

Abstract: A device for use as a subcutaneous injection set is disclosed which has a soft cannula through which a selected medication can be administered to a patient, wherein the soft cannula is adapted for transcutaneous placement by an insertion needle substantially without crimping or kinking. The cannula is supported by and protrudes outwardly from a housing adapted to receive the selected medication. The insertion needle is initially inserted through a septum on the housing and further through the cannula to provide a rigid structure to insert the soft cannula through the patient's skin. The insertion needle and cannula are constructed to prevent longitudinal slippage of the cannula on the needle during the insertion process, thereby preventing undesired crimping or kinking of the soft cannula. After insertion, the needle is withdrawn from the cannula and housing to permit medication delivery to the patient.

Abstract: An improved power supply adapter is provided for plug-in connection to a standard AC power supply receptacle, and to provide a DC voltage to an associated electronic instrument. The power supply adapter comprises a relatively compact case having an end face with a plurality of conductive prongs protruding therefrom for plug-in connection to an AC receptacle, such as one socket of a standard duplex or quad wall outlet or the like. An AC adapter assembly is mounted within the adapter case with the components of the AC adapter assembly arranged generally in-line between the conductive prongs and a power cord adapted for connection to the associated electronic instrument. This in-line geometry permits the adapter case to have a relatively narrow width and low profile height conforming with a single electrical socket, whereby plug-in connection of the adapter to an electrical socket does not obstruct access to adjacent sockets.

Abstract: A variable speed drive system for an induction motor is disclosed which utilizes power factor correction capacitors to allow an induction motor to be driven by a line-commutated inverter using variable phase angle triggering of the thyristers in the inverter to compensate for frequency-induced changes in the operating point of the system.

Abstract: A system within an implantable stimulation device and a method for limiting the extent to which rate-responsiveness can be utilized during low battery periods. A battery threshold detector is utilized to detect when the battery is below a predetermined threshold. The implantable stimulation device then switches to base rate, but with a preset recovery time used to prevent rapid rate change. In an alternate embodiment, the device may then become rate-responsive again, but with a lower allowable maximum sensor rate being used.

Abstract: A cardiac pacing system includes circuitry for verification of capture having an indifferent electrode mounted on the pacemaker connector top. The cardiac pacing system may use one or two bipolar or unipolar leads. Capture is sensed between the indifferent electrode and one of the electrodes on the lead or leads. Either electrode on the lead or leads can be used as the other electrode forming a sensing pair with the indifferent electrode. The electrode is located in the plastic connector top portion of the implanted pacemaker, and may be disposed at a side of the pacemaker, when implanted, facing the interior of the patient, or facing the exterior of the patient.

Abstract: A kit is provided for use in refilling a medication infusion pump of the type adapted for implantation into the body of a patient. The kit comprises a syringe having a plunger mounted for reciprocation within a syringe barrel having a manually operable control valve mounted at a nose end thereof. The syringe further includes a lock for retaining the plunger subsequent to retraction motion with the control valve closed to pull and maintain a vacuum within the syringe barrel. With this construction, the syringe can be connected transcutaneously with a medication reservoir within an implanted infusion pump to aspirate residual medication from the pump. Alternately, the syringe can be used to degas medication within the barrel preparatory to transcutaneous delivery to the pump reservoir. In either case, the syringe is designed for facilitated and safe manipulation to permit rapid pump aspiration and refill at periodic intervals according to patient requirements.

Abstract: An improved process and related apparatus are provided for filling a pressure reservoir of an implantable medication infusion pump with a selected pressure fluid, wherein the pressure reservoir is separated by a movable wall from an adjacent medication chamber. The improved filling process includes vacuum-draw filling of the pressure reservoir with relatively purified pressure fluid in liquid state. The specific quantity of pressure fluid within the pressure reservoir is thereafter calibrated by filling the adjacent medication chamber with a calibration fluid at a predetermined positive pressure, thereby expelling excess pressure fluid from the pressure reservoir. The pressure reservoir is then sealed and the performance characteristics thereof are tested under simulated implantation conditions to confirm the capability of the pressure reservoir to maintain medication within the medication chamber under substantially constant pressure conditions.