Abstract: A patch electrode of the type which is surgically attached to the epicardium for use in an implantable arrhythmia treatment system is disclosed which has one or more regions of exposed electrode mesh on a side of the electrode in direct contact with the epicardium. The mesh is held in a flexible carrier having a periphery between the exposed mesh and the edge of the carrier. A layer of a drug or steroid is carried on the carrier in this peripheral region, the drug or steroid interacting with body fluid and thereby slowly releasing into the surrounding tissue. The drug or steroid may be selected to provide antiarrhythmia therapy, reduce inflammation, retard tissue growth or may be an antimicrobial drug. The layer carried on the carrier may be on surface thereof, contained in a shallow trough in the carrier, or impregnated within the carrier material. The layer may be carried on one or both sides of the carrier.

Abstract: A suture sleeve for anchoring the lead body of an implantable medical device, such as a cardiac pacemaker, includes an elongated tubular member having a lumen for receiving the lead body. The tubular member has external threads for receiving a threaded collar. The tubular member and collar have engaging, tapered surfaces whereby tightening of the collar on the tubular member compresses a portion of the tubular member into gripping engagement with the lead body. The tubular member and collar have surfaces which come into contact upon tightening of the collar so as to limit compression of the lead body and thereby prevent damage thereto.

Abstract: An improved battery pack is provided for short term battery power operation of a medical instrument such as an infusion pump. The battery pack comprises a substantially closed and compact housing one or more rechargeable batteries inaccessibly encased therein, with the battery pack housing being adapted for mounting directly onto the casing of an electronic medical instrument. The batteries are mounted on a base plate beneath a foil shield and a housing cap, both of which are attached to the base plate in a manner precluding nondestructive removal thereof and thereby substantially preventing access to the batteries. The assembled battery pack housing includes seal members for preventing passage of any gases discharged from the batteries into the medical instrument casing, and further defines at least one vent for exhaust passage of such gases to the exterior of the battery pack and medical instrument.

Abstract: A pacemaker having a single integrated interconnect structure is disclosed which combines the functions of a flexible interconnect cable and a protective lid for a hybrid substrate. The integrated interconnect structure is a molded three-dimensional part having a lid portion and a feedthrough portion. An electronic substrate can be mounted onto the integrated interconnect structure wherein electrical conductors formed within the integrated interconnect structure connect the electronic substrate to the battery terminals and to the pacemaker feedthroughs. In one embodiment, the integrated interconnect structure may be adapted to have additional electronic circuitry mounted directly onto a flat inner cavity within the lid portion, thereby enabling electronic components to be easily added or modified without complicating the assembly operations of the pacemaker.

Abstract: A system within an implantable stimulation device and a method for limiting the extent to which any high power consumption modes, such as a rate response mode, 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 from a high current drain mode of operation to progressively lower current drain modes of operation. This configuration allows a significant reduction in current drain at RRT and further prevents the output amplitude from dropping below the capture level and prevents the remaining battery capacity from being rapidly used up.

Abstract: A drive circuit for use with a capacitive load includes two transistors controlled by a drive voltage and connected to the load through an inductor. A supply voltage is alternately connected and disconnected to the circuit to achieve a resonant transfer of energy from the supply voltage. Energy stored in the load is transferred to the inductor and then back to the load, thereby reversing and augmenting the output voltage across the load and providing an instantaneous output voltage many times the supply voltage. Diodes ensure that the current flows in the proper polarity through the transistors.

Abstract: An ultrasonic air-in-line detection system for use in detecting air bubbles in the fluid line of a disposable cassette mounted on a main pump unit is disclosed which utilizes an innovative construction used to attach electrical connectors to the ultrasonic transducers. Rather than wires, a thin flex circuit having a plurality of arms is used, with the flex circuit having a circular conductive pad located at the end of each arm. A circular segment of conductive transfer tape is used to attach each of the conductive pads to the thin layer of conductive metal located on each side of the ultrasonic transducer.

Abstract: An improved blood oxygen sensor apparatus having a special leakage compensation circuit that allows proper initialization of the oxygen sensor regardless or the value of leakage resistance which typically might be present in parallel with the oxygen sensor. During an initialization mode, in which a capacitor arranged in parallel with oxygen sensor is charged by a small initialization current, the leakage compensation circuit monitors the capacitor voltage and controllably increases the current if it is determined that the capacitor is charging at an insufficient rate, due to unspecified leakage resistance. This enables the oxygen sensor to be properly initialized such that it can thereafter accurately measure blood oxygen levels.

Abstract: An implantable tachyarrhythmia control system includes a patch electrode having a sensor integrated therein, such as a piezoelectric sensor, which is capable of monitoring mechanical heart activity. When the patch electrode is sutured to the cardiac tissue, the piezoelectric sensor will be deformed due to the mechanical activity of the heart muscle, and will generate a corresponding electrical signal. The electrical signal from the sensor will exhibit relatively low-frequency periodicity and relatively low amplitude during normal heart activity. In the event of tachycardia or fibrillation, the signal will exhibit excursions beyond those occurring for normal heart activity, and will consequently have a higher energy content. The signal is thus an indicator for the onset of these cardiac events. The signal can be supplied to an implantable defibrillator and can be used as a primary or secondary trigger for initiating defibrillation therapy, such as one or more defibrillating pulses.

Abstract: A suture sleeve for securing the leads of a multiple lead implantable medical device includes lead gripping and anchoring portions. The sleeve has a pair of flexible side walls and longitudinally extending channels for receiving the leads. The side walls of at least the gripping portion have longitudinally extending, confronting, spaced apart edges and comprises two layers one of which is formed of a soft plastic such as silicone and the other of which is formed of a harder but flexible material such as polysulfone. Sutures placed and tied about the gripping portion compress the sleeve about the leads. Tightening of the sutures brings the confronting edges of the gripping portion of the sleeve into engagement thereby precluding further compression of the sleeve and preventing damage to the leads.

Abstract: An arrangement is provided which enables the rapid and effective termination of electrical junctions for an implantable medical device such as a heart pacemaker, a defibrillator, or a cardioverter. A circuit board supporting electronic circuitry is receivable in a housing for the medical device and is provided with a plurality of female connectors on its outer surface. The female connectors are positioned and shaped to receive and guide mating male components into abutting engagement therewith. The mating male components include feedthrough wires which extend between the interior and the exterior of the housing and conductive pins from a battery used to power the medical device. When the male components and female connectors are in abutting engagement, they are fusion welded as by a laser or electron beam.

Abstract: A system and method for terminating a cardiac arrhythmia includes pacing means for stimulating the heart with at least one stimulation pulse during a narrow region of susceptibility (termination window) of the arrhythmia cycle. The location of the region of susceptibility is initially found by delivering the stimulation pulse(s) to the heart in accordance with a prescribed scan pattern. The scan pattern delivers the stimulation pulse(s) at a time during the cardiac cycle such that each successive stimulation pulse is presented to the heart at a slightly different time than was a prior stimulation pulse, thereby assuring that the region of susceptibility or termination window is eventually located. When the arrhythmia is successfully terminated, the location of the successful stimulation pulse within the prescribed scan pattern is stored.

Abstract: An implantable rate-responsive pacemaker is disclosed wherein two or more sensors indicative of physiological demand are utilized in a fashion designed to realize the advantages of both sensors in a circuit producing a rate command signal which is used to operate the pacemaker at an optimum pacing rate which will closely match physiological need of the patient. A rate matrix is used to produce a specific selected rate which is unique to the particular combination of sensor inputs which are being measured at the particular time. In the preferred embodiment, a plurality of rate matrices are provided, with the appropriate rate matrix to be used being selected by a switch matrix which monitors the logic-processed and time-processed signals from the sensors, the outputs of the processing circuitry being used to select a cell in the switch matrix which corresponds to the exact set of conditions currently being encountered by the sensors.

Abstract: An implantable rate-responsive pacemaker is disclosed wherein two or more sensors indicative of physiological demand are utilized in a fashion designed to realize the advantages of both sensors in a circuit producing a rate command signal which is used to operate the pacemaker at an optimum pacing rate which will closely match physiological need of the patient. A switch matrix monitors processed signals from the sensors to select a unique set of numerical coefficients indicated by the processed sensor signals. The selected set of numerical coefficients are used as weighting factors to weight the impact of each of the sensor signals in the calculation of a selected rate.

Abstract: An implantable pacemaker having means for detecting and responding to a premature ventricular contraction (PVC), also includes circuit means for minimizing the likelihood of sensing a PVC when in fact a PVC has not occurred. The circuit means latches the occurrence of any atrial events sensed during the relative atrial refractory period of the pacemaker, whether such atrial events are noise or an early P-wave; and, in response to such latching, disables the PVC detection circuit until certain prescribed events occur, whereupon the PVC detection circuit is re-enabled. The prescribed events that re-enable the PVC detection circuit after it has been disabled include, e.g., the occurrence of a ventricular pulse or sensed R-wave. Further, in the event a PVC is detected and a desired PVC response is invoked, an additional circuit means automatically terminates the PVC response in the event the PVC response becomes stuck.

Abstract: A porous electrode for pacemakers is comprised of a plurality of platinum globules sintered together to form a porous mass of semi-hemispherical shape at the end of a platinum electrode stem. The globules, which are themselves made by sintering together spherically-shaped particles of approximately one micron diameter, provide the globules with an irregular outer surface of high total surface area. The globules have diameters within a critical range of 40-200 microns. The large total surface area of the globules improves the sensing function of an electrode configuration of given size and surface area, while the globule diameters of 40-200 microns have been found to beneficially accommodate tissue ingrowth within the electrode. In a preferred method of making the electrode, the platinum globules, which are formed by sintering together platinum particles of much smaller size, are mixed with organic solvent and organic binder to form a paste.

Abstract: An optical motion sensor is provided for monitoring movement of a mechanical device, particularly such as an infusion pump of the type used for controlled delivery of medication to a patient. The motion sensor includes a disk member mounted upon a selected mechanical output component driven by the infusion pump, such that the disk member undergoes displacement during normal pump operation. The disk member defines a pattern of reflective and substantially nonreflective surface zones which are alternately illuminated by a light source during normal pump operation. A light detector responds to the level of reflection from the disk member to provide an output signal which varies according to disk member displacement. This output signal is connected to a controller for comparison with drive signals supplied to the infusion pump, to verify proper mechanical output operation of the pump.

Abstract: A drive circuit for applying a supply voltage to a sending coil provides resonant coupling of the sending coil with the target coil regardless of changes in the inductance of the sending coil, as long as the resonant frequency of the sending coil is greater than the resonant frequency of the target coil. A controller provides variable delay intervals in the application of the supply voltage, thereby compensating for changes in the sending coil's inductance with the passage of time and proximity effects. The controller examines the reflected voltage induced in the sending coil by changing currents in the target coil to examine the degree of resonant coupling between the two coils and correct any mistuning.

Abstract: An implantable pacemaker provides a paced AV delay that is automatically adjusted to include patient variations in latency conduction, that is, the time interval between a stimulus to the heart and an evoked potential, time due to lead position and specific patient latency. An AV timer, designed to provide a programmed AV interval, starts its timing operation at the generation of an atrial pulse, and restarts the timing operation again at the occurrence of the evoked atrial potential. The evoked atrial potential is typically monitored from a ring electrode of a bipolar lead relative to the pacemaker can (case), although other monitoring configurations are also possible. The length of the AV intrval is programmed to a desired value using conventional programming techniques.

Abstract: A multi-contact connector system for electrically and mechanically connecting a lead for the delivery of electrical energy at a body site to an implantable source of the electrical energy includes a plug connector element carried at a proximal end of the lead which is received in a socket connector element carried on the source of electrical energy. The plug connector element is a radially expandable sleeve with a number of exteriorly exposed contacts respectively connected to conductors contained within the lead. Corresponding contacts are mounted in the interior of the socket connector element. The plug connector sleeve fits over a flexible expansion element contained in the socket connector element. The expansion element is operated by a toggle switch after the connector elements are engaged so as to radially expand.