Abstract: A system for internally sensing the cardiac electrogram in a patient with a cardiac pacemaker is disclosed comprising an implanted electrode that, in combination with the metallic case of the pacemaker which acts as an indifferent electrode, senses cardiac electrical signals and provides them as an input to the pacer electronics. The sensing electrode is appropriately spaced from the pacing electrode and positioned so that cross coupling is minimized to permit sensing of the cardiac electrogram without undue interference from the pacing stimulus and after potentials, and so that the pickup of both R- and P-waves is optimized. The sensed signals may be used to control atrial, ventricular or multichamber demand pacemakers and/or may be telemetered out of the patient for pickup and analysis by external equipment. A flat plate and a preferred cylindrical ring form of electrode are described.

Abstract: A cardiac electrode arrangement is disclosed for use in temporarily pacing the heart of a subject and comprises an electrically-conductive strip surrounded by a layer of biocompatible insulating material, which layer has openings on one face of the strip to permit exposure of a portion thereof for contact with the heart and on the other face removably accommodates and holds the stripped end of a pacer lead in contact with the strip. The electrode may be attached to the heart by clips or a single suture, and the pacer lead can be disconnected from the electrode after use by simply pulling the stripped end from under the insulating layer.

Abstract: A complete system for telemetering and monitoring the functioning of an implanted pacemaker as well as controlling the testing of the functions from a remotely located central facility is disclosed specifically comprising the provision of capabilities for directly and simultaneously transmitting from the pacer, electrical signals indicative of multiple pacer functions, such as, pacer rate, cell voltage, refractory period, heart rate with pacer inhibited, R-wave level and sensing margin, sensing circuit and other component failure, cardiac electrode lead break, and hermetic integrity. The indicative signals are picked up at the patient's location for local analysis and/or telephonically communicated to a remote central monitoring station. The central station may control testing of the pacemaker functions by transmitting command signals back telephonically for coupling through cooperating external and implanted inductances or magnetically controlled switches to the implanted pacer circuitry.

Abstract: A cardiac pacing apparatus of the type having a first signal processing channel which functions in the demand mode is disclosed including a second signal processing channel for detecting electromagnetic interference and causing the pacing apparatus to revert to a safe operating rate in the presence of such interference. In a preferred embodiment, the second signal processing channel has an enhanced high-frequency response with respect to that of the first signal processing channel in order to optimize interference detection. The second channel may receive an input from either a conventional cardiac sensing and pacing electrode, or else a second electrode, remote from the heart, may be provided for interference detection.

Abstract: An hermetically-sealed cardiac pacemaker which may be operated on a single non-rechargeable cell or a magnetic-induction-rechargeable mercury cell that is hermetically sealed along with an outgas alleviating material in a separate container within an integral stainless steel outer case, which case also houses the system electronics. The integral case is formed with an opening in which a closure plate is disposed in a recessed position and sealed about its periphery to the interior of the opening to form a receptacle in the exterior of the casing. The receptacle is filled with a biocompatible material to isolate the seal from the exterior of the casing and the case acts along with the internal electronics during recharging as a charging current regulator system which maintains a substantially constant power transfer from the charging transmitter to the internal receiver despite variations in their proximate spacing.

Abstract: A cardiac pacer system includes a first relatively large contact area electrode for sensing cardiac activity and a second electrode of substantially smaller contact area than the first to apply artificial stimulating pulses to the heart. The first electrode has a sufficiently large contact area to achieve a relatively high sensitivity to cardiac activity and the second electrode has a sufficiently small contact area to generate a relatively high current density at the electrode-tissue interface when the artificial stimulating pulses are applied to the heart. The electrodes are supported in a spaced relationship by an electrically insulating spacer. Each electrode may be directly wired to an appropriate point within the cardiac pacer, and referenced to a common electrical return point by means of a third, common electrode. Alternatively, the first and second electrodes may be connected to the pacer with a single lead, with suitable decoupling circuitry between the single lead and each electrode.

Abstract: A cardiac pacing apparatus includes a trigger pulse generator which generates trigger pulses at a predetermined minimum rate when the natural heart rate fails to exceed the predetermined minimum rate and which follows the natural heart rate when the heart rate is above the predetermined rate, an output pulse generator for generating artificial heart stimulating pulses, a timing interval generator for generating a fixed timing interval in response to the generation of each artificial heart stimulating pulse, and an inhibit gate for selectively applying only those trigger pulses which occur outside the fixed timing intervals to the output pulse generator. The output pulse generator is maximum-rate limited as an inverse function of the fixed timing interval duration regardless of the input rate, and pulses at the minimum predetermined rate, as established by the trigger pulse generator, are generated after an escapement interval in the absence of natural cardiac activity.