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 miniature, hybrid-mountable, accelerometer-based, physical activity sensor for use with a rate-responsive implantable stimulation device is provided. The physical activity sensor is constructed as a cantilever beam having a film of a piezoelectric polymer adhered to each surface of an electrically conductive substrate. The piezoelectric films are highly resistant to fracturing during manufacture and in use, and they provide a strong output signal when stressed in response to bodily accelerations. A pair of electrically conductive supports serve to anchor the physical activity sensor to a substrate and deliver the output signal provided by the sensor to circuitry within the rate-responsive implantable stimulation device. The physical activity sensor is adapted to be mounted directly to conductive traces on a suitable substrate, preferably an implantable stimulation device hybrid.

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: 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 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: 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 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 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: 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 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 stimulation lead having an anti-inflammatory coating on the exposed surface area of the distal tip electrode. The coating is a semi-viscous or gelatinous material having the ability to absorb physiological fluids to provide electrical conductivity through the coating. The coating preferably has a matrix having an innate hypo-inflammatory property which can be combined with drugs and therapeutic agents to deliver the drugs and agents by co-dissolution or diffusion, or alternatively the matrix material can be used as a coating to keep the electrode surface electrochemically clean prior to and during implant.

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.

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 sense amplifier adapted for use with a cardiac pacer or the like includes a constant gain filter, a window comparator circuit and a programmable threshold reference generator circuit. The reference generator circuit generates a programmable window (reference) voltage used by the window comparator circuit to determine whether an input signal, amplified by the constant gain filter, exceeds the window voltage. The reference generator circuit is based on a bipolar junction device having an adjustable emitter area through which a constant current flows. The emitter area is adjusted in response to a control signal. As the emitter area changes as controlled by the control signal, the voltage across the device changes. In a preferred embodiment, a parallel combination or network of switched bipolar junction devices is used to realize the adjustable emitter area.

Abstract: An in-line, multipolar proximal connector assembly for an implantable stimulation lead is provided which incorporates at least one sensor. Advantageously, the present invention uses straight conductive rods, or wires, to electrically connect the proximal terminals to a multilumen lead body. The straight conductive rods enable the diameter of the lead assembly to remain small. Additional terminals can easily be added by simply decreasing the spacing between terminals and adding additional conductive rods. In one embodiment, insulating spacers are premolded to include protruding portions which interlock with the ring terminals. Recesses within the insulating spacers are dimensioned to self-position the ring terminals a precise distance from the pin terminal according to precise dimensions defined by the VS-1 (or other) standards. In another embodiment, the terminals are injection molded.

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 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 body implantable lead including a sheath, an electrode sleeve secured at a distal end of the sheath, a rotor body positioned within the sleeve, a fixing helix secured to a distal end of the rotor body, a torsion spring secured to a proximal end of the rotor body, and a rotation guide formed between the electrode sleeve and the rotor body which includes a helical groove formed on either the rotor body or the electrode sleeve and at least one guide pin formed on the electrode sleeve or the rotor body, respectively.