Abstract: A hermetically sealed pressure transducer suitable for implantation in a human body. A pressure sensitive circuit is fabricated using contemporary silicon technology. The pressure sensitive circuit is sealed in an oil-filled chamber formed within a titanium cylinder having a glass substrate bottom and a thin titanium top. According to one embodiment, the pressure sensitive circuit contains a sealed inner chamber at a known pressure, thereby measuring pressure relative to a known value. A second embodiment vents the pressure sensitive circuit to produce a relative pressure measurement. A grill protects the assembly and aids insertion into the desired area. A lead connects the transducer to an implantable sensing circuit.

Abstract: An iontophoretic device in which the polarity of the electrodes is reversible. There is a current source and a pair of electrodes. A polarity control between the current source and the electrodes determines the direction of current flow through and between the electrodes. A timer circuit communicates with the current source and the polarity switching circuit to automatically ramp down the current, switch polarity and then ramp up the current after the polarity has been switched, thereby permitting the iontophoretic process to take place under both electrodes with one application.

Abstract: A body implantable stimulator having an output capacitance that is periodically charged to a predetermined energy level and discharged through an electrode coupled to body tissue. The discharge pulse width is controlled by a semiconductor switch and after a short delay the capacitor is recharged rapidly to its original charge. The recharge current is regulated by a differential circuit responsive to the voltage on a reference capacitor and the output capacitor, both capacitors being coupled to the active electrode.

Abstract: A single pass atrial-ventricular transvenous pacing lead wherein the atrial branch has a positive fixation device. The proximal end of the lead has a standard electrical connector for coupling both atrial and ventricular electrodes to an implantable pulse generator. The lead is bifurcated at a point near or above the superior vena cava during normal transvenous insertion. The atrial and ventricular branches are of a fixed length from the point of bifurcation to the distal tip. The ventricular branch preferably employs a passive fixation device such as tines to maintain the ventricular electrode within the right ventricular apex. The atrial branch is positioned in the normal manner under control of a stylet to obtain optimal sensing and stimulation thresholds. This position is maintained using an active fixation device. Preferably the active fixation device is a helix which is screwed into the atrial wall by rotating the atrial connector pin and conductor coil.

Abstract: Pacer output circuitry for providing biphasic stimulation pulses to heart tissue at a voltage twice the supply voltage. Additionally, the circuit may be configured to sense the intracardiac electrogram in a unipolar or bipolar configuration.

Abstract: Technique for permitting ease of mapping of the myocardial tissues during implantation of a myocardial electrode. The technique employs the use of a disposable exploring needle located on the distal end of the implantable lead assembly. The permanent electrode is attached to the exploring needle by being embedded into an electrically conducting material of the exploring needle. The implanting physician explores the electrical characteristics of the myocardial tissues using the exploring needle. Upon finding the desired electrode location, the exploring needle is removed and discarded and the electrode is permanently attached in the manner customary in the prior art.

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: A programmable pacemaker pulse generator capable of operating in several atrial and ventricular pacing modes, having atrial and ventricular sense amplifiers and output circuits and programmable memory and clock controlled digital timing circuits for selectively delivering stimulating pulses to the heart in an atrial synchronous mode of operation. The ventricular sense amplifier has a blanking and refractory period following the sensing of a ventricular heartbeat or the occurrence of a stimulation pulse. Delay means are operatively connected to the atrial sense amplifier operate to trigger the generation of a ventricular stimulating pulse after an A-V delay interval following a sensed atrial depolarization.An atrial blanking interval extends for the A-V delay interval and until after the expiration of the ventricular blanking interval. Programmable upper date intervals are also provided.

Abstract: A dual chamber pacing lead requiring but a single transvenous pass for implantation. The ventricular electrode has tines for sustaining acute and chronic fixation. The ventricular electrode is coupled to a first conductor which is space wound having an insulation sheath. The proximal end of the first space wound coil protrudes slideably from a first connector pin of a bifurcated connector assembly. An optional stylet may be inserted into the first space wound coil to assist in ventricular placement. A second space wound coil is slideably located over the first space wound coil. The second space wound coil serves as a support means rather than a conductor. The proximal end of the second space wound coil is fixedly attached to the connector assembly. The first space wound coil protrudes near the distal end of the second space wound coil.

Abstract: A programmable pulse generator capable of operating in several atrial and ventricular pacing modes having atrial and ventricular sense amplifiers and output circuits, programmable memory and clock controlled digital timing circuits and a depletable power source. End-of-life sensing circuits detect first and second end-of-life depletion levels. Magnet activated end-of-life test circuitry responds to the presense of none, one or both of the end-of-life depletion level signals to alter the operating modes and pacing rates to indicate the orginally programmed mode and the level of depletion to an observer. Preferably, the pulse generator is operated in the asynchronous DOO or VOO modes and at non-programmed test rates to provide the indication.

Abstract: A service kit for splicing body implantable leads having inner and outer coaxially-arranged coil wire conductors insulated from one another. A conductive pin having a distal portion with an outside diameter less than the inside diameter of the inner coil has a barbed tip that is screwed into the inner conductor coil. A shoulder portion of the conductive pin having a larger diameter bears against and retracts the inner coil with respect to the outer coil as the distal portion is screwed into the coil lumen. An insulating sleeve over the shoulder portion assures that the conductive pin does not contact the outer conductor coil. An adaptor housing physically holds the end of the coaxial lead being spliced, the conductive pin and the insulating sleeve. A first set screw through the adapter housing contacts the conductive pin allowing electrical contact thereto.

Abstract: A gamma ray scintillation camera generating (X,Y) spatial coordinate and Z energy signals relative to detected radiation events. The system provides for calibration of the camera Z signal response as a function of camera face location. In addition, the camera signals are converted to their digital equivalents subsequent to which the apparent coordinate locations of detected events as determined by the camera are corrected to their true spatial coordinates based upon correction information stored in the system.

Abstract: An implantable medical device to deliver cardioverting energy to cardiac tissue in synchrony with detected ventricular depolarizations. The energy renders refractory, areas of the heart associated with a reciprocating or automatic tachycardia, thus reverting these tachyarrhythmias to normal sinus rhythm without the risk of stimulating the heart during the vulnerable portion of repolarization.

Abstract: A body implantable lead having a two-piece stylet. An inner solid portion of the stylet enables a shape to be imparted to the stylet to allow proper maneuvering of the lead during implant. A second portion of the stylet is slideably located coaxially about the first portion. The second portion of the stylet permits the imposition of a torque at the distal end of the implantable lead by the turning of a knob fixedly attached to the proximal end of the second portion of the stylet. The second portion of the stylet is a helically wound coil. The two-piece stylet is inserted into the proximal end of the body implantable lead. The distal end of the body implantable lead is located in the position desired through the use of the solid inner first portion of the stylet in which a bend or other desired shape has been introduced. The body implantable lead is permanently attached to the muscle tissue by a fixation device activated through the torque supplied by the second portion of the stylet.

Abstract: A structure for use as an electrode on a pacing lead to be located some distance proximal to the distal end of the pacing lead. Two short lengths of wire having high electrical conductivity are cut to size. The coils of the outer conductor are welded together at the desired location of the ring electrode of the lead. The two short lengths of wire are welded to the outer conductor of the lead at the desired location of the ring electrode. An insulating sheath having an inside diameter close to the outside diameter of the outer conductor is slid over the outer conductor. The flexibility of the insulating sheath is sufficient to permit encasing of the two short lengths of wire, though the insulating sheath is caused to protrude at the two places directly over and corresponding to the two short lengths of wire.

Abstract: A demand cardiac pacemaker of the type having sense amplifier circuitry for detecting the occurrence of natural heart activity which establishes a first level representative of sensed extraneous repetitive noise and a second level greater in absolute value than the reference by an amount representative of sensed heart activity. Circuitry differentially responsive to the difference between the reference and second level detects the occurrence of natural heart activity. The sense amplifier circuitry is blanked, that is disconnected from the terminals coupled to the heart, for a blanking interval following stimulation to avoid saturation of the sense amplifier stages and the erroneous detection of a pacing stimulus. Any reference level voltages developed by extraneous repetitive noise are retained during blanking to prevent the differential circuitry from interpreting the noise signal sensed at the end of the blanking interval as a heart signal.

Abstract: A marker channel telemetry system for use with a pacemaker or other medical device for transmitting event identifying codes to a remote receiver to indicate the occurrence of specific events such as sensed and paced events in a dual chamber pacemaker. The structure of the system includes latches to store event information and for forming the marker codes. The system also includes a serial telemetry transmitter for transmitting the data to the remote receiver.

Abstract: A digital computer system is described as comprising an input data circuit, a processor for executing a program stored in a memory to process the inputted data, a depletable energy source (e.g., a battery) for energizing the elements of the computer system, and a power control circuit for selectively controlling the drain imposed upon the energy source in accordance with the data input into the system and the program executed by the processor. In an illustrative embodiment of this invention, the power control circuit is operative in at least three modes of operation, namely off/rest, power down, and operating. In the off/rest mode, the power control circuit imposes a minimum power drain upon the depletable energy source. An operator may manipulate a switch or actuation means to apply a transition signal to the power control, whereby the computer system is disposed from its off/rest mode to its power down mode.

Abstract: Apparatus and method for accurately measuring the energy output of a pacing system analyzer or other pulse generator. Voltage measurements are made across the output capacitor before and after the pulse is generated. These voltages are measured by a microprocessor using an analog-to-digital converter and various gating and control circuitry. By using a known value of capacitance for the output capacitor along with the voltages measured before and after the stimulation pulse is generated, the microprocessor can calculate the total amount of energy within the stimulation pulse. This value is displayed on an integral display device. Through the use of additional circuitry, measurements may be made for both atrial and ventricular stimulation pulses in a dual chamber stimulation device. Provisions have also been made for measuring the output energy for constant voltage pulse generators. This technique employs measurement of pulse width.

Abstract: A multiple-mode pacer which automatically switches from an atrial synchronous mode to a ventricular inhibited mode when the intrinsic atrial rate drops below a preset hysteresis rate. This mode switching prevents atrial bradycardia from resulting in the delivery of closely spaced ventricular stimulating pulses.