Abstract: A digital phase-locked looped generates a clock signal synchronized with a carrier signal modulated by amplitude shift keying (ASK). During periods when no carrier signal is present, the generated clock signal coasts at the frequency of the carrier signal most recently present, rather than trying to phase-lock on noise. A binary controlled digital oscillator generates the clock signal. A phase detector determines the difference between the phase of the carrier signal, when present, and the local clock signal. When the average amplitude of the carrier signal exceeds a prescribed threshold level, the phase detector output is sampled and passed to an integrator circuit, where the phase difference is integrated. The output of the integrator circuit is applied to a pulse generator, causing the pulse generator's duty cycle to change proportionally.

Abstract: A high speed digital telemetry system (10) includes a transmitter (12) and a receiver (14), at least one of which is adapted for use in an implantable device. The transmitter includes a data encoder (14), modulator (16), transmitting coil (20), and transmitting coil drive circuit (18). The data encoder examines prescribed incoming data bits and prior encoded data bits, generating an encoded data stream (36) that includes a data transition only when a prescribed correlation is noted amongst the examined bits. The modulator modulates a carrier signal (34) with the encoded data stream, causing a phase reversal of the carrier at each data transition of the encoded data stream. The transmitting coil drive circuit applies the modulated carrier (38) to the transmitting coil. The receiver includes a receiving coil (22) and associated amplifier (24) and bandpass filter (26) for detecting the transmitted modulated carrier.

Abstract: An atrial rate based programmable pacemaker including means for preventing the heart from being paced at an upper rate limit for prolonged periods of time is disclosed which paces the heart at a rate that follows or tracks the atrial rate up to the upper rate limit of the pacemaker, at which point the pacemaker stimulates the heart at the upper rate limit, but also continues to monitor the atrial rate. If the monitored atrial rate exceeds a second upper rate limit, a fast atrial arrhythmia or tachycardia condition is deemed to exist, and the pacemaker automatically switches from its existing mode of operation to an alternate mode of operation in an attempt to break or terminate the fast atrial condition. Alternate embodiments include using an external activity or physiological sensor to control the pacing rate in the new pacing mode, and the inclusion of means for periodically verifying that atrial sensing is occurring, and means for automatically adjusting the sensitivity of the atrial channel as required.

Abstract: A rate-responsive pacemaker which includes a conventional programmable pulse generator, a physiological sensor, and a processor is disclosed which generates heart stimulation pulses on demand, or as otherwise programmed, as controlled by a rate control signal which is derived from the physiological sensor. The physiological sensor generates a raw signal which varies as a function of some physiological parameter, such as activity level to provide some indication of whether the heart rate should increase or decrease, and hence whether the pacemaker should change the rate at which pacing pulses are provided. The processor converts the raw signal to the sensor-indicated rate signal in accordance with a selectable transfer relationship which defines the sensor-indicated rate signal as a function of a set of discrete sensor level index signals.

Abstract: A device for use as a rate-responsive pacemaker is disclosed in which the pacing interval is controlled by the amount of energy contained in a raw signal generated by a suitable physiological sensor and processed by an energy converter to generate an output energy signal coupled to the pacemaker control circuits to adjust the pacing interval. The energy converter may be a rectifying amplifier and an integrating circuit, a voltage controlled oscillator whose frequency is measured over a suitable time interval using a time interval generator and a counter with the output of the counter being used by the control circuits of the pacemaker to vary its pacing interval, or means for measuring energy content of the raw signal and storing that measurement in memory and periodically processing it to alter the transfer characteristics of the rate-responsive pacemaker.

Abstract: A unitary piston cap and boot seal for use in a medication infustion system is disclosed which is mounted on a rigid piston contained in a cylinder disposed in a cassette. The piston cap and boot seal, which are made of a flexible, elastomeric material, effectively both form the pumping element disposed in the cylinder, and prevent contamination of the pump through use of a rolling seal. The device may be sterilized by gas, since a tortuous path affording passage to gas is included in the retaining skirt mounted around the outer diameter of the pump cylinder.

Abstract: A feedthrough connector for an implantable medical device, combines the connector function with the feedthrough function and eliminates the need for the cast epoxy connector previously used on such devices. The feedthrough connector includes a barrel assembly having open and closed ends. The open end of the assembly has an opening for receiving a slidably inserted electrical lead. The barrel assembly includes cylindrical metal conductive portions separated by cylindrical ceramic insulating portions. Spring contacts are mounted on the inside of the metal portions and are adapted to make electrical contact with the appropriate contacts of an electrical lead when the lead is inserted into the connector. The outer side of the metal portions are electrically connected to the appropriate electrical circuit within the housing, and the open end of the barrel assembly is bonded (welded) to the device housing so that the inside of the device can be hermetically sealed.

Abstract: A fluid delivery monitoring and control apparatus for use in a medication infusion system is designed for use with a disposable fluid pathway that incorporates a sterile cassette containing pumping elements and sensor interfaces. The apparatus comprises a multi-segment drive mechanism, controller, and monitoring system. Fluid pumping is accomplished by controlling DC motors in the drive mechanism, each of which is coupled to two valves and a reciprocating piston for an individual pumping channel in the cassette. The motor is geared down to provide an appropriate maximum speed and torque. A cam sequentially actuates an inlet valve, piston, and an outlet valve in the cassette. A range of fluid delivery rates is achieved by periodically sending pulses to the motor. The output flow rate of the pump is maintained by a digital feedback controller which uses closed-loop feedback control to provide accurate regulation.

Abstract: A method of screening potential recipients of an implantable medication infusion system including an implanted intraperitoneal catheter is disclosed which seeks to select only those candidates who will have a high degree of resistance to catheter blockage due to fibrotic tissue growth. By checking certain physical parameters in candidates for an implantable catheter, and by declining to implant in those candidates who have higher than desirable levels of the parameters, catheter survival in those patients chosen for implant is maximized. The four parameters used are blood triglyceride level, blood cholesterol level, the level of insulin dosage per day, and mean blood glucose (MBG) level, with the first two being the more accurate parameters.

Abstract: A pacemaker lead analyzer for measuring impedance during standard operation of an implanted pacemaker. The analyzer makes separate measurements of lead impedance during each heart signal and each pacing pulse. A moving average of measured parameters is maintained and recurring deviations from the norms are noted in separate event counters for subsequent analysis of the noted events as possible indications of impending failure of an implanted lead.

Abstract: An adjustable template device for pacemaker ECG analysis is similar to a slide rule with a transparent window portion which can be laid over an ECG trace to aid in its analysis. A frame for the template has a back member and a cover member connected together with rivets, with the cover member having cutout portions through which various scales printed on the back portion can be seen. A series of movable transparent plastic sheets slide back and forth independently in the frame to allow measurement of time intervals on the ECG trace. Fiducial marks on the movable sheets indicate time intervals by their positions with respect to scales on the back member. AV, AE, MT, PVAR, and pacing intervals can all be set simultaneously on the template. A photocopy of the template overlying the ECG trace can be made to provide a permanent record.

Abstract: The improved transvenous implantation method of the present invention involves entering a vein of a patient, translating through the vein to the patient's cardium atrium, anchoring onto the atrial lateral wall, puncturing the atrial lateral wall and forming a hole therein, exiting the atrium through the hole to the pericardial space and inserting the object into the pericardial space. The present invention also includes a method for the transvenous repair of a wound in the atrial lateral wall.

Abstract: A device for use to detect air in a fluid line between a medication infusion reservoir such as an IV bottle or bag and an IV injection set or a medication infusion pump is disclosed which utilizes a detector apparatus which clamps onto a segment of tubing. The detector uses a light source to generate light which is directed into the tubing, and two light detecting devices, one of which is used to determine whether or not the tubing is properly installed in the detector, and the other of which is used to detect the presence of air in the segment of tubing. The detector works equally well with transparent, translucent, or opaque fluids and includes means for ensuring that the detection system is functioning normally.

Abstract: A cassette identification system for use with a medication infusion system having disposable cassettes which are mounted onto a main pump unit is disclosed which uses an optical sensor module to read the identifying bits from the cassette. The identification indicia contained on the cassette each either pass light through a portion of the cassette, or diffuse the light to prevent it from passing through the cassette. The optical module is mounted on the main pump unit, and includes light sources and sensors for each of the identification indicia on the cassette; the system may use either redundant or non-redundant coding for identifying the cassettes.

Abstract: A disposable cassette containing a fluid pump for use with a main unit including apparatus for driving the pump is disclosed which cassette utilized a piston-type pump in conjunction with active valves to pump fluid. The inlet and outlet channels in the cassette are formed by a diaphragm covering open channels in the cassette body, and the same diaphragm is used to form the active valves, which are actuated by valve actuators in the main pump unit. Additional features of the cassette include an air trap upstream from the pump, and an integral clamp which allows priming of the cassette.

Abstract: A system for detecting an occlusion in a fluid line is disclosed which can detect occlusions in the downstream or patient side of a disposable cassette containing a fluid pump thereon. The cassette includes a pressure diaphragm and is for installation onto and use with a main pump unit including a pressure transducer therein for monitoring fluid pressure downstream of the pump. The system utilizes control circuitry to provide an alarm in the event of a patient-side occlusion, and the occlusion detection system works when the system is configured as any of a number of difference device types, including both a flow controller emulation and several different infusion pump configurations.

Abstract: In a first embodiment, hysteresis is provided in a rate-responsive pacemaker to allow for natural AV synchrony when possible. In the absence of natural SA node signals, the heart is stimulated at a rate determined by the sensing of physiological need. When a natural heart signal is detected, the hysteresis is activated to extend the escape interval by a predetermined amount which is related to the sensed physiological need. The stimulating pulses are inhibited as long as normal heart activity is sensed. The extension of the escape interval under such conditions eliminates possible competition between normal activity and the paced stimulation. In a second embodiment automatic mode switching is provided in a dual chamber pacemaker to allow for more efficient operation at higher heart rates. When the heart rate (natural or paced) exceeds a prescribed level, such as 90 beats per minute, the pacemaker operates in a single chamber mode, such as VVI.