Abstract: A suture sleeve assembly for gripping and anchoring the lead body of an implantable medical device, such as a cardiac pacemaker, includes a tubular member adapted to receive the lead body. Disposed about the tubular member is a collar movable longitudinally along the tubular member from a first, open position to a second position in which the collar compresses a portion of the tubular member into gripping engagement with the outer surface of the lead body. The collar is fabricated of a material that is stiffer than that from which the tubular member is fabricated.

Abstract: A ribbon conductor set and related method of production and installation are provided for electrically interconnecting components in an implantable medical device, such as a heart pacemaker unit or the like. The ribbon conductor set is formed by die cutting and/or stamping a thin plate of conductive material to define a plurality of conductor ribbons supported from a frame. The ribbon set and supporting frame are shaped for seated placement into a fixture to orient the conductor ribbons in predetermined array to extend between electrical components on the fixture, such as between connector blocks and feedthrough terminals of a heart pacemaker unit. The fixture thus supports the conductor ribbons for facilitated connection to the electrical components, such as by welding, after which the resultant subassembly may be further processed as by encapsulation within a cast epoxy head or the like.

Abstract: An atrial tracking dual-chamber pacemaker and method of use thereof for terminating a pacemaker-mediated tachycardia (PMT). The pacemaker includes means for determining whether the present heart rate exceeds a tachycardia reference rate, and if so, whether a PMT-indicating sequence of a tracked P-wave, including a retrograde P-wave followed by a V-pulse, occurs repetitiously for at least a predetermined number of cardiac cycles. The pacemaker includes means for measuring the interval between a P-wave and a V-pulse (PVI) and sets the PVI to 250 milliseconds when the measured value is less than 250 milliseconds. The pacemaker issues a PMT-terminating timed atrial pulse which is timed from a retrograde P-wave by a time equal to the PVI, plus a delay of about 25-100 milliseconds. In the event the atrial pulse fails to terminate the PMT, the process is repeated after a fixed number of cardiac cycles has occurred.

Abstract: An implantable arrhythmia treatment system includes a sensor which generates an electrical signal corresponding to a physiological characteristic of a patient, the physiological characteristics and thus the electrical signal exhibit a change given the onset of an arrhythmia. The electrical signal is supplied to a fibrillation detector in an implantable housing, which initiates an appropriate treatment sequence upon the detection of the onset of the arrhythmia. Simultaneously with initiating the treatment sequence, the fibrillation detector causes, either by direct connection or by telemetry communication, the generation of an alarm signal which informs the patient that the sequence has been initiated, so that the patient knows that a treatment pulse is about to be released. The implantable unit includes circuitry responsive to a signal externally generated by the patient which prevents the release of the defibrillating pulse. If the patient feels no need for such a pulse, i.e.

Abstract: An adjustable output level transmitter includes a direct current energy source, an L-C tank circuit and a switching means for sequentially coupling the capacitors of the tank circuit to the direct current energy source and ground. The output signal frequency is equal to the resonant frequency of the L-C tank circuit and the output signal level is a function of which capacitors of the L-C tank circuit are sequentially coupled to the energy source. The circuit functions in a Class D mode with the inherent advantages of minimal power loss and very high efficiency. Due to the manner of switching utilized, the output signal frequency is very stable and unaffected by the mode of capacitor switching.

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 bipolar electrode assembly for attachment to heart tissue for use with a pacemaker. The assembly has a hub member with a helical screw-in coil that acts as a first electrode and is used to attach the assembly to the heart tissue. The assembly further comprises a plurality of appendages that extend from the hub member and each have an electrode segment of electrically conductive material. The electrode segment of the appendages can act together as a single second electrode, or alternatively as a separate, independent electrodes, which may selectively be used for pacing or sensing. The electrode segments not only act as electrodes, but also allows heart tissue to grow directly into the conductive material to help secure the assembly to the heart. The assembly also has apertures and grooves for suture connection of the assembly to the heart. Methods of manufacturing the assembly and connecting the assembly to a heart are also described.

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: 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: 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: 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: 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 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 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-part molded pacemaker connector that meets the precise requirements imposed by the VS-1 standard, yet does not require complex or expensive machining of individual parts. Advantageously, the pacemaker connector is made from a plurality of individually molded parts, with each individual part being designed to readily allow the insertion of seals and other connector components, prior to joining the parts together. The connector includes three molded pieces: a body tip, a body ring, and an entrance connector which are adapted to be joined during assembly. The connector further includes a garter spring, and preferably, two annular sealing rings. A tip connector block is insert-molded into the body tip. A conductive tube, which forms the ring connector, is insert-molded within the entrance connector. The body ring provides appropriate spacing between the tip connector block and the ring connector.

Abstract: A rate-responsive pacing method and system senses the minimum blood oxygen saturation in the right atrium of a patient's heart and uses such minimum blood oxygen saturation as a control parameter for indicating the muscular activity of a patient. Because the oxygen content of the venous blood in the right atrium varies significantly as venous blood from all parts of the body is introduced therein, evidencing differing levels of oxygen demand throughout the patient's body, the minimum oxygen content of the venous blood provides an accurate and reliable measure of those portions of the patient's body experiencing the greatest oxygen demand, i.e., experiencing muscular activity. A rate-responsive pacing system includes means for sensing the minimum oxygen content in the right atrium over a prescribed time interval, and using such minimum oxygen content as a control parameter for adjusting the rate of the pacemaker.

Abstract: A self-adjusting rate-responsive pacemaker includes a conventional programmable pulse generator, a physiological sensor, and a processor, all packaged within an implantable case. The pulse generator generates heart stimulation pulses on demand, or as otherwise programmed, as controlled by a sensor-indicated rate signal. The sensor-indicated rate signal is derived from a raw signal obtained from the physiological sensor, and provides some indication of whether the heart rate should increase or decrease. The processor converts the raw signal to the sensor-indicated rate signal in accordance with a desired relationship (FIGS. 2, 3, 7A, 8). A minimum sensor signal value sets the minimum rate at which the pacemaker generates stimulation pulses, and a maximum sensor signal value sets the maximum rate at which the pacemaker generates stimulation pulses.

Abstract: A ribbon conductor set and related method of production and installation are provided for electrically interconnecting components in an implantable medical device, such as a heart pacemaker unit or the like. The ribbon conductor set is formed by die cutting and/or stamping a thin plate of conductive material to define a plurality of conductor ribbons supported from a frame. The ribbon set and supporting frame are shaped for seated placement into a fixture to orient the conductor ribbons in predetermined array to extend between electrical components on the fixture, such as between connector blocks and feedthrough terminals of a heart pacemaker unit. The fixture thus supports the conductor ribbons for facilitated connection to the electrical components, such as by welding, after which the resultant subassembly may be further processed as by encapsulation within a cast epoxy head or the like.

Abstract: An improved telemetry system for telemetering digital data from an implantable tissue stimulator such as a heart pacemaker. A carrier signal is pulse modulated in accordance with either or both of stored digital data and a digitized electrocardiogram signal, for coupling onto an electrical lead connected directly to the heart. This arrangement facilitates the transmission of substantially higher data rates than previously could be achieved.