Abstract: A device such as a cardiac pacemaker or other implantable biomedical device, and method of operation thereof, containing one or more switchable circuits. A control system, preferably incorporating a microprocessor, controls predetermined changes of the operating characteristics of the switchable circuits. In a cardiac pacer embodiment, a circuit such as the input amplifier can be switched to have different characteristics, e.g. filter setting and sensitivity, during predetermined portions of the pacer cycle. Further, the operation of a circuit can be monitored over a plurality of operating cycles, with controlled switching of the circuit characteristics as a function of cumulative monitored circuit performance. A specific example of the invention is shown for changing characteristics of a filter circuit used in a pacer which adjusts the pacer rate as a function of determined stimulus-T wave time interval.

Abstract: A pacemaker and method of cardiac pacing employing the Tx mode of rate control, having means for automatically terminating the refractory period after sensing of an evoked T wave following a delivered stimulus. The pacemaker also is capable of overriding a natural rate and delivering one or more stimulus pulses so as to obtain a Tx rate determination during what would otherwise be inhibited pacer operation.

Abstract: Apparatus for producing programmable timing signals, having a microprocessor element with means for carrying out DMA operations when said microprocessor element is in a DMA mode, memory interconnected with said microprocessor element and containing a stored program and a plurality of data words stored at predetermined addresses for selection by said microprocessor when in said DMA mode, comprising controller means for transforming received data words into timing signals, connecting means for interconnecting said microprocessor element, said controller and said memory, said controller having means for setting said microprocessor in said DMA mode upon receipt of a predetermined signal generated by said program, means for receiving data words directly from said memory under control of said microprocessor when said microprocessor is in said DMA mode, and means for generating a two state timing signal corresponding to the data content of one or more such received data words.

Abstract: A biomedical system such as a pacemaker system having an implantable pacemaker and external apparatus, with communications capability for communicating between the implanted device and the external apparatus, characterized by the implanted device having means for cyclically transmitting event and device timing data representative of each prior device interval, the external apparatus having means for receiving and storing the data and for graphically constructing a graphic output representative of the timing and event information over a plurality of device cycles. Graphic output preferably includes a linear timing graph representative of timing functions of the implanted device.

Abstract: Apparatus and method for treatment of tachycardia, wherein when tachycardia is determined a portion of a patient T-wave is sensed and utilized as indicating the end of the cardiac refractory interval. One or more anti-tachycardia stimuli are delivered in timed relation to the sensed T-wave. The initial T-wave from which the first A-T stimulus is timed may be evoked by delivery of an early stimulus.

Abstract: A programmable dual chamber cardiac pacemaker is provided which provides improved means for responding to sensed high atrial rates. The pacemaker monitors the sensed high atrial rates and determines whether they are physiological or not, and automatically controls the operative atrial refractory period as a function of whether or not the atrial rate is physiological. The pacemaker is permitted to go into a Wenckebach mode of operation only when it is determined that a sensed high atrial rate is physiological, and that under other conditions will automatically go into a block mode of operation.

Abstract: A pacemaker system incorporates an implantable pacemaker and a plurality of electrodes, electrodes preferably being on a pacing lead for a single chamber pacemaker, or a pair of such leads for a dual chamber pacemaker. Programmable connection means are provided for connecting the pacemaker output to a selected combination of lead electrodes, the selection being changed during each pacer cycle to optimize the choice of unipolar and bipolar operation for given pacemaker events. In one mode, the system employs bipolar QRS sensing and unipolar pacing and T-wave sensing. In another mode, the system employs bipolar QRS sensing and pacing, and unipolar T-wave sensing.

Abstract: An improved cardiac pacemaker adapted to be programmed into one of a plurality of given modes of operation, including dual chamber modes, and in particular synchronous operation for pacing the patient's ventricle following detection of natural atrial heartbeats. The pacemaker has means for monitoring the time relationship between delivered ventricular stimulus pulses and next succeeding atrial heartbeats, for determining the occurrence of pacemaker induced retrograde P waves, or pacemaker caused tachycardia. The timing, and thus the rate of sensed P signals is processed to determine the desirability of establishing a special P sense window for looking for the occurrence of P signals at rates above a normal maximum operating rate, in which event the stability of the V-A timing is monitored in accordance with predetermined criteria to determine the existence of pacemaker mediated tachycardia, which may be broken up by skipping a ventricular stimulus.

Abstract: A self-adjusting voltage regulator circuit on a CMOS chip, for use with CMOS digital and/or analog circuit, providing a voltage which is selected in accordance with the characteristics of the chip to optimally current control operation of CMOS circuits on this chip. The voltage regulator circuit has a reference CMOS pair with a predetermined geometry, and current means are provided for driving a current through said reference pair which is adjusted to operate the pair at a desired point of current controlled operation. The voltage across the reference pair is utilized to provide the regulated voltage to other CMOS pairs, which pairs have respective geometries of predetermined relation to the reference pair geometry, whereby the regulated voltage and the relative geometry provide current controlled operation of each such CMOS pair.

Abstract: A dual chamber pacemaker system is disclosed with means for operating in one or another of alternate rate adaptive modes. The pacemaker incorporates an atrial synchronous mode, wherein, pacing rate is determined as a function of sensed atrial signals. It also incorporates a T.sub.x mode, wherein pacing rate is controlled by a sensed QT interval, and an extra sensor mode, wherein pacing rate is controlled as a function of at least one sensed body parameter. The pacemaker comprises means for automatically testing the applicability or appropriateness of the mode currently in use, and for automatically selecting the appropriate rate control mode.

Abstract: A dual chamber pacemaker having means for operating in different pacing modes, including dual chamber modes, contains the capability of switching into a fixed rate ventricular pacing mode and of sensing early atrial signals without affecting the ventricular pacing timing. The timing of a plurality of such sensed early atrial signals is analyzed to determine if they represent retrograde P waves and, if so, the indicated V-A conduction time. The pacemaker atrial refractory time is adjusted so that, during dual chamber operation, the atrial refractory time extends past the time of anticipated retrograde P waves, thereby optimizing the setting of the atrial refractory period for avoidance of pacemaker mediated tachycardia. Other pacing conditions may also be adjusted in response to the determined patient V-A time.

Abstract: Method, kits and reagents for the simultaneous, kinetic spectrophotometric analysis of blood serum samples for multiple components. Pairs of components which may be simultaneously analyzed are: cholesterol and triglyceride; glucose and urea; uric acid and gamma glutamyl transferase; calcium and magnesium; albumins and total protein.

Abstract: A pacing system and method of programming the rate of said system is disclosed, wherein the pacemaker comprises circuitry for receiving a first group of simple on-off magnetic pulses which are accumulated and translated into the decades portion of the desired heartbeat rate (in bpm), and also for receiving a second group of pulses which are translated into the units count of the desired pacing rate in bpm. The circuitry provides that an initial portion of the programming signal is inspected relative to predetermined criteria, so that such initial portion acts also as an enabling key for accepting the overall programming signal. The doctor simply applies a simple hand held magnet t times according to the desired tens component of the programmed rate in bpm, maintains the magnet applied for at least a predetermined number of pacer intervals, and then applies the magnet u times corresponding to the units component of the desired heart rate, thereby programming the pacer to operate at tu bpm.

Abstract: A physiological stimulating system includes improved means for minimizing the polarization that results at the stimulus site, thereby enabling enhanced detection of evoked responses. In the pacemaker embodiment, the stimulus signal comprises positive recharge pulses immediately before and immediately after the negative stimulus signal, the recharge pulses being adapted in a time duration and amplitude such that the total current delivered to the stimulus site, (e.g., a patient's heart) by the stimulus signal is substantially zero.

Abstract: A combined linear and circular drive mechanism for driving a spindle in an up or down direction and also in a circular path about an axis parallel to the spindle. The mechanism has a dual or compound nut which is driven to rotate in a fixed plane so as to drive a spindle threaded therethrough in an up or down direction. The dual nut mechanism has a pair of nut components having respective eccentrically positioned threaded openings, the openings being displaced from each other such that one of the nut components engages the threaded spindle to drive it in a first direction while it is being carried in a circle, and a second nut component engages the spindle to drive it in the reverse direction, also while the shaft is being rotated in a circle.

Abstract: A switching power delivery means for use with a relatively low voltage power source, adapted to be used in conjunction with a converter for providing a raised voltage supply to a load, wherein the load is characterized by having a first circuit portion which is voltage sensitive and draws a low current, and a second circuit portion which draws a high current and is relatively insensitive to supply deviations, comprising a switching circuit alternately connecting said respective circuit portions through respective converters to the supply so that the voltage sensitive circuit is not affected by the loading of the high current circuit.

Abstract: A physiological stimulating system includes improved means for minimizing the polarization that results at the stimulus site, thereby enabling enhanced detection of evoked responses. In the pacemaker embodiment, the stimulus signal comprises positive recharge pulses immediately before and immediately after the negative stimulus signal, the recharge pulses being adapted in a time duration and amplitude such that the total current delivered to the stimulus site, (e.g., a patient's heart) by the stimulus signal is substantially zero.