Abstract: An improved medical electrode is particularly adapted for transmitting DC currents. The electrode includes (1) an electrically conductive substrate electrically connected to a stud member and chemically inert with respect to the electrically and ionically conductive material, such as a gel, coupling the electrode to the skin of the user, and (2) a predetermined amount of an electrically-conductive material, preferably silver, disposed on the substrate in spaced relationship to the stud member and interfacing with the electrically and ionically conductive material.

Abstract: An improved flow through ion sensing electrode and a method for producing it. The electrode is formed of bilumen plastic tubing using one lumen as the sample path and the other lumen as a sensing chamber. By permeating a portion of the tubing with an ion selective material, an ion selective membrane integral with the chamber wall is produced. A preferred embodiment also incorporates a reference electrode.

Abstract: A combination ion sensing and reference electrode and a method for producing it. The electrode is formed of bi-lumen plastic tubing using one lumen as sensing chamber and the other as a reference chamber. A portion of the sensing chamber extends distally relative to the reference chamber, and is permeated with an ion selective material by soaking that portion in a solution containing the ion selective material. The method of manufacture is thereby simplified and sealing of the chambers is improved.

Abstract: The frequency-modulated demodulator is provided in which the frequency-modulated signal as having a relatively narrow range of frequency modulation is demodulated by providing a pulse which corresponds to the positive half-wave cycles of the signal and then generating an extended duration pulse from the initiation of the first pulse produced to the second pulse produced in two consecutive cycles. In this manner every other cycle of the FM demodulated signal provides an output pulse which substantially corresponds to the duration of one cycle of the FM signal. A high frequency clock on the order of 1,000 times faster than the frequency of the extended duration signals is gated through for substantially the entire width of the extended pulse duration. The number of clock pulses that are gated through or counted to provide an indication of the frequency signal, a sampled basis corresponding to every other cycle of the FM signal.

Abstract: A data telemetry system for use with implanted medical devices for transmitting digital and analog data to a remote receiver by enabling different combinations of fixed and variable value current sources according to a telemetry logic code to energize a tank coil and produce a ringing type of variable frequency RF signal.

Abstract: The programming of pulse intervals and the inhibition of the output of an implanted cardiac pacemaker are disclosed. The occurrence of either an output pulse from the implanted unit or of cardiac activity allows for synchronization of the programming unit with the implanted device so the external programmer can control the pulse timing sequence of the implanted unit. The implanted unit can be programmed after each pulse, or as required, to obtain a pulse sequence which may be used to provoke, or terminate, tachyarrhythmias, thus enabling non-invasive electrophysiologic studies, or therapeutic stimulation.

Abstract: A waveform detection system for use in a pacemaker for distinguishing normal beats from ectopic or abnormal beats for example, such as those involving ventricular tachycardia, ventricular flutter or fribrillation, premature ventricular beats, supraventricular tachycardia, retrograde conduction; and in dual chamber or atrial applications those involving atrial tachycardia and atrial flutter or fibrillation. The term "abnormal" is employed herein to mean all abnormal beats including those specified above. In the system of the illustrated embodiment a sense amplifier is employed for initiating a counter in response to a detected cardiac event and a voltage controlled oscillator is used for converting the instantaneous value of the applied waveform to a bit rate delivered to the counter. The morphology or shape of the physiological waveform is represented by a number present in the counter at the end of the counting cycle which allows for a therapy decision to be made.

Abstract: A programmer for a pacemaker which has telemetric capabilities is disclosed. The programmer, in addition to being able to program the pacemaker through telemetric transmission of programming codes can receive digital and analog (including marker) information from the pacemaker for remote display and utilization, and for program modification in response thereto, if desired. Implementation of the programmer is accomplished partly by circuitry which includes pulse duration measurement circuitry for measuring time duration intervals of incoming RF telemetric signals and partly by a firmware program stored in the programmer.

Abstract: An apparatus for treating a patient which induces an electric current in the body through external application of an electromagnetic field. The apparatus includes means for controlling the magnitude of the induced electric current by sensing the electromagnetic field and automatically controlling its strength. The sensing may be accomplished through time multiplexed use of the field inducing coil or through the use of a separated, dedicated coil.

Abstract: An implantable medical device to deliver cardioverting energy to cardiac tissue in synchrony with detected ventricular depolarizations having a DC-DC flyback converter. The primary coil of the converter is periodically coupled and decoupled to ground by a timing circuit to effect charging of a high voltage output capacitor from a low voltage source through the secondary coil. A supply voltage detector alters the time period of the timing circuit to regulate the amount of current drawn by the primary coil. As the low voltage power supply depletes, its impedance increases tending to prolong the charging time of the output capacitor. Further regulating circuitry alters the one-shot time period to avoid loading down the supply voltage which could affect operation of other circuits.

Abstract: A magnetic-field, noise-cancelling transceiver is provided by a dual-coil antenna circuit. In the receive mode, two identical coils, connected in series opposition, cancel noise signals common to both coils and receive desired signals present at only one coil. Capacitance in parallel with the series-opposed coils establishes the resonant frequency of the receiver, antenna circuit. In the transmit mode, the two coils, connected in series opposition, have their non-adjacent terminals clamped to ground via two pairs of oppositely-poled diodes, one pair on each non-adjacent terminal. The transmitter signal, coupled to the junction of the two coils through a capacitor, generates additive magnetic fields by causing equal currents to flow in each coil from the common junction, to their respective diode junctions, to ground through the respective, oppositely-poled diode pairs. Series resonance is established by the transmitter coupling capacitance and the parallel combination of the two coils.

Abstract: A cardiac output monitor of the type including an ultrasound crystal for use as a doppler flowmeter. The monitor is designed for mounting directly to a blood vessel, and is provided with a novel fixation apparatus which allows for easy and secure attachment to the blood vessel. The fixation apparatus includes two parallel fixation wires especially adapted for location in the blood vessel wall, without the danger of piercing the vessel wall.

Abstract: A tissue stimulator of the type which provides short intervals of stimulation followed by longer intervals of rest is provided with a fail-safe system for turning off the stimulator if the stimulation interval exceeds a predetermined maximum interval. A timer times each "on" interval. If the "on" interval exceeds the predetermined maximum, the timer times out and shuts off stimulation.

Abstract: A threaded pacing electrode assembly for use in implantable electrical leads. The electrode is provided with an exposed portion adapted to make electrical contact with body tissue and with a cylindrical portion proximal to the exposed portion provided with a helical screw thread. A conductor coil which has an inner diameter smaller than the outer diameter of the cylindrical portion is mounted to the exterior of the cylindrical portion, coiled within the screw thread. A transparent insulating sleeve covers the cylindrical portion, is frictionally retained by the thread, and assists in maintaining the conductor coils in contact with the cylindrical portion.

Abstract: A rate responsive pacer which paces the heart at a rate dependent on detected variations in the stroke volume of the heart.

Abstract: A physiologic cardiac pacer operable in the DVI or A-V sequential pacing mode or the DDD or fully automatic pacing mode senses for the omission of an R-wave from an implantable cardiac pacer during the A-V interval. If the pacer does not sense a R-wave during the A-V interval the V-A interval is timed out immediately following the A-V interval and an atrial pacing pulse is issued at the end of the V-A interval. In the event, however, that an R-wave is sensed during the A-V interval, a flag is set and then the entire A-V interval is to be timed out, at which time the state of the flag is determined. If an R-wave was previously issued, a ventricular pacing pulse is not issued to the pacer at the end of the A-V interval, whereas if the flag is not set it is transmitted to the pacer.

Abstract: An improved method for producing ion-selective membranes having a desired shape and of a desired plastic, for incorporation in ion-sensing electrodes, and the electrodes incorporating these membranes. This method allows the use of preformed polymeric members having the desired shape to produce ion-selective membranes, allowing simplified production of ion-sensing electrodes, as well as combination ion-sensing and reference electrodes.

Abstract: A lead for implantation in the epidural space has an inflatable balloon which is sealed against a first side of the lead so it inflates away from the first side. The balloon contacts walls of the epidural space and urges an electrode on the first side against the dura. A syringe for inflating the balloon has a spring to absorb travel of a plunger actuator when fluid pressure in the balloon exceeds tension of the spring.

Abstract: A programmable cardiac pacemaker pulse generator utilizing digital circuitry for controlling the provision of cardiac stimulating pulses. The pulse generator is capable of having the rate, the pulse width, the pulse amplitude, the refractory period, the sensitivity and the mode of operation programmed. In addition, the pulse generator can have the output inhibited and can respond to programming signals causing a threshold margin test to be performed, effects of closure of the reed switch overridden, a hysteresis function added and a high rate exceeding the normal upper rate limit programmed. Many of the programmable functions of the pulse generator can either be programmed on a permanent or a temporary basis. The pulse generator further includes means for signaling the acceptance of a programming signal, and means to reset the program acceptance circuit if extraneous signals are detected as programming signals.

Abstract: The programming of pulse intervals and the inhibition of the output of an implanted cardiac pacemaker are disclosed. The occurence of either an output pulse from the implanted unit or of cardiac activity allows for synchronization of the programming unit with the implanted device so the external programmer can control the pulse timing sequence of the implanted unit. The implanted unit can be programmed after each pulse, or as required, to obtain a pulse sequence which may be used to provoke, or terminate, tachyarrhythmics thus enabling non-invasive electrophysiologic studies, or therapeutic stimulation.