Abstract: There is provided an implantable system and method for monitoring pancreatic beta cell electrical activity in a patient in order to obtain a measure of a patient's insulin demand and blood glucose level. A stimulus generator is controlled to deliver stimulus pulses so as to synchronize pancreatic beta cell depolarization, thereby producing an enhanced electrical signal which is sensed and processed. In a specific embodiment, the signal is processed to determine the start and end of beta cell depolarization, from which the depolarization duration is obtained. In order to reduce cardiac interference, each stimulus pulse is timed to be offset from the QRS signal which can interfere with the pancreas sensing. Additionally, the beta cell signals are processed by a correction circuit, e.g., an adaptive filter, to remove QRS artifacts, as well as artifacts from other sources, such as respiration.

Abstract: There is provided an implantable system and method for monitoring pancreatic beta cell electrical activity in a patient in order to obtain a measure of a patient's insulin demand and blood glucose level. A stimulus generator is controlled to deliver stimulus pulses so as to synchronize pancreatic beta cell depolarization, thereby producing an enhanced electrical signal which is sensed and processed. In a specific embodiment, the signal is processed to determine the start and end of beta cell depolarization, from which the depolarization duration is obtained. In order to reduce cardiac interference, each stimulus pulse is timed to be offset from the QRS signal which can interfere with the pancreas sensing. Additionally, the beta cell signals are processed by a correction circuit, e.g., an adaptive filter, to remove QRS artifacts, as well as artifacts from other sources, such as respiration.

Abstract: There is provided an implantable system and method for monitoring pancreatic beta cell electrical activity in a patient in order to obtain a measure of a patient's insulin demand and blood glucose level. A stimulus generator is controlled to deliver stimulus pulses so as to synchronize pancreatic beta cell depolarization, thereby producing an enhanced electrical signal which is sensed and processed. In a specific embodiment, the signal is processed to determine the start and end of beta cell depolarization, from which the depolarization duration is obtained. In order to reduce cardiac interference, each stimulus pulse is timed to be offset from the QRS signal which can interfere with the pancreas sensing. Additionally, the beta cell signals are processed by a correction circuit, e.g., an adaptive filter, to remove QRS artifacts, as well as artifacts from other sources, such as respiration.

Abstract: A system and method of providing for cardiac pacing which incorporates modulation of the pacing rate in order to minimize variations in ventricular power output, e.g., variation related to patient respiratory phases. In a preferred embodiment, pacing rate is increased during inspiration relative to expiration, to restore a measure of the normal rate modulation which occurs in a normal person. Patient respiration is monitored and a respiration signal is processed to determine the timing of rate modulation. Parameters representative of respiratory changes, such as right ventricular volume and right ventricular blood pressure are also monitored and, together with respiration amplitudes changes, are used to determine an incremental rate signal for controlling the extent of rate variation.

Abstract: There is provided an implantable system and method for monitoring pancreatic beta cell electrical activity in a patient in order to obtain a measure of a patient's insulin demand and blood glucose level. A stimulus generator is controlled to deliver stimulus pulses so as to synchronize pancreatic beta cell depolarization, thereby producing an enhanced electrical signal which is sensed and processed. In a specific embodiment, the signal is processed to determine the start and end of beta cell depolarization, from which the depolarization duration is obtained. In order to reduce cardiac interference, each stimulus pulse is timed to be offset from the QRS signal which can interfere with the pancreas sensing. Additionally, the beta cell signals are processed by a correction circuit, e.g., an adaptive filter, to remove QRS artifacts, as well as artifacts from other sources, such as respiration.

Abstract: There is provided an implantable system and method for monitoring pancreatic beta cell electrical activity in a patient in order to obtain a measure of a patient's insulin demand and blood glucose level. A stimulus generator is controlled to deliver stimulus pulses so as to synchronize pancreatic beta cell depolarization, thereby producing an enhanced electrical signal which is sensed and processed. In a specific embodiment, the signal is processed to determine the start and end of beta cell depolarization, from which the depolarization duration is obtained. In order to reduce cardiac interference, each stimulus pulse is timed to be offset from the QRS signal which can interfere with the pancreas sensing. Additionally, the beta cell signals are processed by a correction circuit, e.g., an adaptive filter, to remove QRS artifacts, as well as artifacts from other sources, such as respiration.

Abstract: There is provided a system for automatically responding to insulin demand without any need for external monitoring or injecting of insulin into the diabetic patient. The system provides for sensing glucose levels internally, and responding by stimulating either the pancreas or a transplant of pancreatic islets in order to enhance insulin production. The enhancing stimulation is delivered at a rate greater than the burst rate, or is otherwise controlled so that the depolarization burst constitutes a greater portion of each islet electrical cycle, thereby resulting in increased insulin production. The system also provides for continuous glucose monitoring, and reacts to sensed hypoglycemia by delivering stimulus pulses timed to reduce the burst durations, and thus to inhibit insulin production.

Abstract: A rate responsive pacemaker is provided having the capability of automatically adjusting the lower rate limit (LRL) for sleep, or nighttime. The pacemaker has a temperature sensor for determining patient blood temperature, and processes patient blood temperature data to obtain an average daily low value of nighttime blood temperature. The pacemaker monitors blood temperature to determine a drop below a threshold which is coupled to the average daily low value, as well as when the rate of temperature change exceeds a predetermined limit, these two coincident conditions suggesting onset of nighttime and/or sleep. Lower rate limit is decremented, preferably by a predetermined amount at onset of nighttime, and is automatically incremented when patient blood temperature and/or time of day indicate the end of nighttime.

Abstract: A system and method for sensing and providing an indication of one or more diabetes-related blood constituents of a patient, the system being based upon an ECG sensor which processes patient ECG signals, either surface, or intracardiac or epicardial, for determining a measure of a blood constituent such as insulin or glucose, or both insulin and glucose. The system has processing capability for correlating selected parameters of the ECG signal with patient blood insulin or blood glucose, to provide the insulin or glucose level. Additionally, the system is provided with input capability for enabling the patient to input data such as the time of meal intake, which is representative of glucose intake, which data is incorporated in making a determination of patient insulin need. The system can be in a first external wearable embodiment, or in a second implantable embodiment which utilizes a pacing-type lead for picking up intracardiac or epicardial signals.

Abstract: A pacemaker is provided having an improved circuit for obtaining a measure of battery end-of-life. The EOL detector includes an input stage with a current mirror output providing a current which is proportional to the current being consumed by the pacemaker circuitry, and thus being expended by the battery. The proportional current is directed to charge a capacitor, which is periodically discharged at a constant current, following which the battery goes through repeated cycles of charging and discharging. A measuring circuit measures the time of capacitor discharge, thereby providing a measure of battery energy discharge during the interval that the capacitor was charging. The interval counts are accumulated to provide an overall count representative of battery expenditure, and thus of pacemaker EOL.

Abstract: A method and apparatus for measuring the depletion level (depth of discharge) of a lithium-iodine battery in an implantable medical device. A first set of measurements are made to determine the internal impedance of the battery, and a second set of measurements are made to determine the geometric capacitance of the battery, which has been found to correlate closely to the depth of discharge of the battery. The measurements are all made while the pacemaker is first temporarily decoupled from the medical device circuitry. The first measurements are made during a time window following a known change in resistive load across the terminals of the battery, and are capable of being correlated with 1-kHz qualification testing data made on the battery at the time of manufacture. The second measurements are made when the known load is periodically coupled and decoupled to the terminals of the battery at a rate of 80-kHz.

Abstract: A cardiac pacemaker and method of operation of such pacemaker is disclosed comprising a single lead having conventional ventricular pacing and sensing electrode means as well as atrial sensors adapted to be positioned in the patient's atrim without any contact with the atrial wall, for sensing atrial wall movement and for generating information signals representative of the atrial wall movement. The free-floating atrial sensor is utilized in providing information for making a determination of a number of cardiac conditions, including analysis of direction of P waves to determine whether sensed signals are anterograde or retrograde.

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 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 circuit is disclosed for providing automatic detection of end of life of a battery source, particularly a lithium iodine type battery source characterized by a sharply increased internal resistance characteristic near end of life. The circuit periodically samples the short circuit output current of the source, the sampling being done at a high switching speed and for an extremely short time duration so that power consumption is minimized and only the resistive component which causes the knee in the resistance characteristic is measured. In the embodiment as incorporated in a cardiac pacer device, detection of the internal resistance knee is utilized to cause a step change in an operating characteristic of the pacer, such as stimulus rate, whereby end of life can be accurately monitored.

Abstract: An implantable programmable pacer is disclosed which incorporates a program logic system for receiving magnetic signals from a simple magnet source applied external to the patient, and for translating the simple magnetic signals into logic signals for re-programming selected pacer parameters. The circuitry of the programming system is adapted to react to predetermined timed sequences of application of the external magnetic signal, which timed sequences are correlated with successive intervals of the pacer stimulus generator. The programming system is adapted to interpret predetermined patterns of external application of a magnetic field as instructions for re-programming respective operating parameters.

Abstract: A cardiac pacer for providing stimulus signals for pacing a human heart, adapted to utilize a lithium-type battery source having an internal resistance which increases with the energy depletion of such source, and having an interface circuit adapted to transfer power from the lithium-type battery source to the circuitry for providing stimulus signals, which interface circuit provides transfer characteristics which are a programmed function of said lithium source internal resistance.

Abstract: A low current drain amplifier system, adaptable for use in cardiac pacers and other applications requiring low current drain operation, having an amplifier path comprising transconductance amplifier means characterized by having the circuit characteristic of a current source at its output, the transconductance amplifier means direct driving an active circuit having a high impedance input, and a current source supply for maintaining fixed current operation of the amplifier system elements. In the preferred embodiment, the amplifier path contains a first OTA operating as an amplifier of received signals, the first OTA having its output direct coupled to an input of a second OTA which operates as a comparator, the output of the comparator OTA being direct connected to an IC transistor element.

Abstract: A demand pacer, such as a cardiac pacer for delivering cardiac stimulus pulses on demand, having an oscillator producing an output which is normally gated for delivery, a low current drain amplifier which is substantially insensitive to voltage source variations for amplifying received natural signals, and logic circuitry for performing a plurality of functions including resetting the oscillator following each received natural signal. In the absence of interference, reset of the oscillator is blocked for a refractory period following either a delivered stimulus pulse or a detected natural signal, and means are provided for inhibiting delivery of a stimulus signal at time of oscillator reset. Current source configurations are utilized for supplying power to the amplifier and logic portions, and the amplifiers are also interfaced into a current driver, which techniques contribute to extremely low power consumption and insensitivity to power supply variations.

Abstract: A pacer having a DC to DC converter for use with a relatively low voltage power source, and for providing a raised voltage supply to a load 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. A method is provided for alternately delivering power from a battery source to respective circuit portions of a stimulus delivery system.