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 myocardial lead having a tissue stimulating electrode attached via an insulated conductor to an epicardial pad the electrode embedded in the myocardial tissue of either the ventricles or the atria, for use as a pacing and/or sensing electrode. The myocardial electrode is configured to be pulled into position with a suture needle and thread. The myocardial electrode of the lead is designed to be highly reliable, to reduce exit block and fibrotic tissue growth, and to be utilized for extended periods even though designed to be implanted within the relatively thin myocardial muscle of a pediatric patient.

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: A rate-responsive pacemaker includes programmable hysteresis means for automatically extending an escape interval, EI.sub.0, in the presence of sensed intrinsic cardiac activity, and returning the escape interval to its initial value in the presence of pacemaker-stimulated (paced) cardiac activity. The escape interval sets the rate at which stimulation pulses are generated on demand in the absence of sensed intrinsic cardiac activity. The initial value of the escape interval is selected to be the lessor of: (a) a programmed escape interval (determined from a minimum programmed rate), or (b) a sensor-indicated escape interval (determined from a physiological or metabolic sensor used as part of the rate-responsive pacemaker). In addition to the hysteresis mode, a scan mode is optionally provided wherein the escape interval, EI.sub.0, is gradually extended (lengthened) in small incremental steps if no intrinsic activity is sensed during the prior escape interval.

Abstract: A patch electrode including a generally oval-shaped metallic mesh affixed to a polymer insulation backing and an insulation frame, and further including a plurality of specially designed lattices which divide the metallic mesh into a plurality of windows or apertures. The windows effectively act as smaller electrodes distributing the higher current densities inward from each of their own individual edges.

Abstract: A method and apparatus for determining the actual capacitance of a capacitor in a cardiac stimulating device in order to determine the potential necessary to store a desired amount of energy on the capacitor, are provided. The discharge curve of the capacitor is measured during re-forming to determine the time constant of the capacitor and the dumping resistor, and hence the actual capacitance.

Abstract: An ICD/pacemaker device provides a shocking pulse whenever it senses cardiac activity indicative ventricular fibrillation by standard means and a unique algorithm to respond to low amplitude ventricular fibrillation that would not be expected to be recognized/sensed by standard means. The ICD/pacemaker device further provides stimulation pulses on demand to a patient's heart whenever cardiac activity is not sensed and determines whether a given stimulation pulse has caused capture. If capture has not occurred, the energy of the stimulation pulse is increased by a predetermined amount and capture is retested. If the energy of the stimulation pulses increases up to a maximum value without causing capture, the generation of further stimulation pulses is stopped, and the ICD/pacemaker device presumes that low amplitude ventricular fibrillation is present. When fibrillation is sensed or presumed to be present, a shocking pulse is generated.

Abstract: An autocapture system within an implantable pulse generator automatically maintains the energy of a stimulation pulse at a level just above that which is needed to effectuate capture. The electrical post-stimulus signal of the heart following delivery of a stimulation pulse is compared to a polarization template, determined during a capture verification test. A prescribed difference between the polarization template and the post-stimulus signal indicates capture has occurred. Otherwise, loss of capture is presumed, and a loss-of-capture routine is invoked that increases the energy a prescribed amount to obtain capture. Periodically, and/or at programmed intervals or events, the capture verification test is performed. During the capture verification test, the pulse generator determines a polarization template for a particular stimulation energy and for each of a plurality of sensitivity or threshold settings. A determination is also made as to which sensitivity settings yield capture.

Abstract: A system and method for preventing atrial competition during sensor-driven operation of a dual-chamber pacemaker includes means for sensing atrial activity during an atrial refractory period. Atrial competition is avoided by either: (1) generating an atrial competition prevention (ACP) interval upon the detection of any atrial activity during the relative refractory portion of an atrial refractory period, and preventing any atrial stimulation pulses from being generated for the duration of such ACP interval; or (2) shortening the atrial refractory period in the event that the sensor-driven rate of the pacemaker begins to approach a rate that might place atrial stimulation pulses near the end of the unshortened atrial refractory period.

Abstract: A dual-chamber implantable pacemaker configured to operate in the DDD or DDDR mode automatically adjusts its AV (or PV) interval to an amount just less than the natural conduction time of a patient, thereby assuring that ventricular pacing occurs in a patient's cardiac cycle at a time near when a natural ventricular contraction (an R-wave) would occur. The pacemaker includes a pulse generator that generates ventricular stimulation pulses (V-pulses) at the conclusion of a pacemaker-defined AV (or PV) interval if no natural ventricular activity (an R-wave) is sensed during such AV (or PV) interval. The AV (or PV) intervals are automatically adjusted by the pacemaker to be just less than the natural conduction time sensed by the pacemaker, where the natural conduction time is the time between atrial activity (a sensed P-wave or a delivered A-pulse) and the subsequent natural ventricular activity (R-wave).

Abstract: A low-power band-pass filter for use in a cardiac pacer includes a single operational amplifier connected in circuit relationship with a plurality of switched capacitors that function as bilinear resistors. Each bilinear resistor comprises a switch for coupling a first lead of a capacitive element to a first terminal and for coupling a second lead of the capacitive element to a second terminal in response to a first state of a control signal, and for coupling the first lead of the capacitive element to the second terminal and for coupling the second lead of the capacitive element to the first terminal in response to a second state of the control signal. Thus, the bilinear resistor switches or oscillates the electrical orientation of the capacitive element between the first terminal and the second terminal in response to the first and second states of the control signal. The invention also includes a method of operating such an implantable filter circuit.

Abstract: A universal cable connector includes a plurality of different sized connectors adapted to mate with the proximal connectors of different sized implantable leads. The cable connector attaches to a system analyzer and enables the system analyzer to interface with whatever implantable leads are connected to the connector block, thereby allowing the system analyzer to perform desired tests, such as threshold-determining tests, using the implanted leads. An adapter cable and clamp is also provided that allows an electrical connection of the proper polarity to be established between an implantable cardioverter-defibrillator (ICD) and the cable connector block while the ICD is connected to a patient and is operating, thereby permitting the system analyzer to monitor the performance of the ICD.

Abstract: A dual-chamber implantable pacemaker automatically adjusts its AV interval so that any ventricular stimulation pulses generated by the pacemaker at the conclusion of the pacemaker-defined AV interval occur at a time in the cardiac cycle that avoids fusion with the natural ventricular depolarization of a patient's heart. The AV interval is set using a search sequence that sets the AV interval value to be on one side or the other of the natural conduction time of the heart, and incrementally changes the AV interval value until it crosses over the natural conduction time interval. The cross-over point is manifest by the occurrence of an R-wave, where an R-wave had previously been absent, or the absence of an R-wave, where an R-wave had previously been present. A final AV interval value is then set as the AV interval value at the cross-over point, adjusted by appending an AV margin thereto.

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 pacing lead for use with a cardiac pacemaker having a multilumen tubing for the lead body and at least one ring electrode or electrical contact located between the distal and proximal ends of the pacing lead. The ring electrode includes axially aligned bores therethrough, the bores corresponding to the locations of the lumens within the multilumen tubing. A stabilizing element assures that the interconnection between the multilumen tubing and the cylindrical electrode is secure.

Abstract: A defibrillator patch lead having a connecting element interconnecting an electrical conductor and a wire mesh electrode pad. The connecting element includes a body portion which has a slot cut therein into which a portion of the wire mesh electrode is inserted and securely bonded, preferably by laser welding. The connecting element further includes a female connector portion which is designed to mate with a male core sleeve. The core sleeve includes a channel for receiving a first conductor therein, which is then electrically and mechanically connected (e.g., by either welding or crimping). The core sleeve also includes an orifice for receiving a second conductor, which is subsequently electrically and mechanically connected (e.g., by either welding or crimping) between the core sleeve and the connecting element. Advantageously, the combination of the core sleeve, two conductors, and the connecting element have superior pull strength over conventional methods of attachment.

Abstract: A bifurcated lead adapter or lead used with an implantable stimulation device, such as a pacemaker, forms part of a stimulation system and method that senses depolarization of the ventricular muscle tissue, and in response thereto, generates a stimulus (composed of a single pulse or multiple closely-spaced pulses) that is delivered to translocated muscle tissue wrapped around the ventricle of the heart, thereby causing the translocated muscle tissue to contract in synchrony with the sensed ventricular depolarization. In one embodiment, a pacemaker operates in the single-chamber triggered stimulation mode analogous to VVT mode. A bifurcated bipolar lead adapter has a proximal connector that is connected to the pacemaker's bipolar female input/output connector. The adapter couples the anode electrode of the pacemaker's bipolar input/output connector to a first female distal connector, and couples the cathode electrode of such bipolar input/output connector to a second female distal connector.

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 electrical conductor assembly utilized, for example, in a defibrillator patch lead to interconnect a pulse generator and monitoring unit, and a wire mesh electrode pad. The electrical conductor includes a Teflon insulated drawn brazed stranded (DBS) wire cable which is wrapped in a drawn filled tube (DFT) wire multifilar coil encased in a biocompatible insulative tubing.

Abstract: A compact connector assembly for an implantable medical device includes a receptacle for receiving the proximal end of a coaxial bipolar lead having a distal end attachable to a desired tissue location. The receptacle includes an open end for receiving the proximal end of the lead and a closed end carrying a conductive pin. The pin has a portion inside the receptacle projecting toward the open end thereof and adapted to make electrical contact with one of the lead conductor terminals. The proximal end of the lead has a conductive socket for receiving the projecting portion of the pin inside the receptacle. An adapter terminal may be used to convert the proximal end of the lead to the industry VS-1 standard.