Abstract: A system for long term monitoring of an internal patient medical parameter having an external reference and means to correct the internal measurements of the parameter via external measurements taken by the external reference. A coordinating device makes the correction and makes available a histogram-based record of the parameter over time. This information can be used to reprogram an implantable device or for other therapeutic or diagnostic purposes. Pressure sensor embodiment is detailed.

Abstract: An implantable system providing cardiac anodal stimulation (AS) as a system for effecting hyperpolarization of myocardial cells of a heart chamber to enhance the relaxation thereof in the diastolic phase and to thereby enhance cardiac function. The AS system is optimally timed to be delivered in an AS delivery interval following an AS delay interval timed from a preceding ventricular depolarization or pacing pulse to effect maximal cardiac relaxation. The sub-threshold AS pulse or train of pulses is increased in energy (amplitude) and/or decreased in energy to and from a peak energy level gradually rather than abruptly. The AS characteristics are optimized in an initialization process that determines the AS characteristics that provide the optimum blood pressure parameters and thereafter continually or from time to time in a confirmation process.

Abstract: A physiologic rate responsive pacer which alters the pacer's escape interval in response to the patient's respiratory minute ventilation derived from the electromyogram of selected respiratory muscle groups. The directly detected electromyogram (EMG) signal is amplified and band passed filtered, processed to remove any electrocardiogram (ECG) or pacing impulse signal, full-wave rectified, processed to develop a moving time average signal from which the peak, the maximal slope, and the average slope of the EMG moving time average may be calculated and processed in conjunction with the inspiratory and expiratory times between successive slope detections of the moving time average EMG to develop a rate control signal representative of minute ventilation.

Abstract: There is provided a system and method for increased data transmission from an implanted pacemaker when the pacemaker is in magnet mode. Pacemaker data including, e.g., pacemaker operating conditions, pacing events and patient events, is outputted by changing the asynchronous pacing rate to selected ones of available rates, and with a predetermined sequence, enabling read out of the data on an EKG strip chart. In a preferred embodiment, data-encoded pace pulses with intervals corresponding to selected rates are delivered in a predetermined sequence with fixed rate non-data intervals. For example, four pulses are delivered at 85 ppm followed by one or more data-encoded pulses, each data-encoded pulse being at 90, 95 or 100 ppm, whereafter the sequence is repeated with additional data-encoded intervals. The combination of rates for each of the data-encoded intervals represents the pacemaker data, and can be decoded by observing an EKG strip taken during the pattern of pace pulses.

Abstract: A cardiac pacemaker with an analog telemetry system. A calibration circuit within the pacemaker is adapted to provide a reference signal of known character to the pacemaker's telemetry system. The reference signal is transmitted across the telemetry link as if it were an actual cardiac signal, and received by an external programmer. Since the reference signal has known, predetermined qualities, the programmer can automatically calibrate and scale the telemetry signal from the pacemaker, thereby increasing the accuracy of the telemetry channel. The increased accuracy is particular useful in assessing rejection of a transplanted heart, which is known to be associated with a 15% decline in the peak R-wave amplitude of the cardiac signal.

Abstract: An implantable medical device with a ceramic enclosure has a novel multi-layered ceramic feedthrough substrate in place of a prior art glass-to-metal feedthrough substrate, leading to lower costs and a higher feedthrough density. Use in a metal enclosure is also disclosed.

Abstract: A tissue electrical stimulator and electrical pulse waveform are described. The stimulator or pulse generator may deliver the pules preferably through an endocardial electrode to pace a heart but could be used for other tissue such as nerves or to deliver defibrillation pulses through other means. A preferred circuit is described employing timing of a gate voltage level on an output transistor for the discharge capacitor(s) of the pulse generator. The waveform has a leading edge starting above zero volts and ramps upward for an initial fraction until a saturation voltage is reached and then ramps downward.

Abstract: A pacemaker control method and apparatus for determining the presence of atrial tachyarrhythmias uses a true interval value and compares it to a predetermined tachy value. The true interval value is updated based on the presence of far field R waves in PVARP that meet certain sequencing criteria. The criteria selected allows the control method and apparatus to reduce or eliminate event sequences that will generate false positive tachy detection and subsequent mode switching, while still allowing for the detection of tachy events in PVARP.

Abstract: A system and method for communicating with a medical device implanted in an ambulatory patient and for locating the patient in order to selectively monitor device function, alter device operating parameters and modes and provide emergency assistance to and communications with a patient. The implanted device includes a telemetry transceiver for communicating data and operating instructions between the implanted device and an external patient communications control device that is either worn by or located in proximity to the patient within the implanted device transceiving range. The control device preferably includes a communication link with a remote medical support network, a global positioning satellite receiver for receiving positioning data identifying the global position of the control device, and a patient activated link for permitting patient initiated personal communication with the medical support network.

Abstract: A dual chamber pacemaker is provided having capability for adjusting the AV escape interval so as to optimize the timing of delivered ventricular pace pulses for therapy of patients with cardiomyopathy. The pacemaker system continually monitors to determine when a delivered pace pulse results in a fusion beat, and periodically adjusts the AV escape interval in accordance with the percentage or rate of incidence of such fusion beats. In one specific embodiment, the pacing system determines the percentage of delivered ventricular pace pulses which are followed by fusion beats over a predetermined number of intervals, and decrements AV escape interval when such percentage is not below a predetermined minimum. The pacing system also periodically increments AV escape interval when the rate of fusion beats is acceptable, thereby providing a closed loop system for maintaining the AV interval at an optimally long value consistent with maximizing full capture by delivered ventricular pace pulses.

Abstract: A method and apparatus for variable rate cardiac stimulation, wherein sudden drops in the rate of delivery of stimulation pulses are avoided by means of rate smoothing and peak rate support functions. In one embodiment, circuitry in a cardiac pulse generator detects atrial events and maintains an updated value of the A-A time intervals between certain atrial events. If a preset ratio or total of these A-A intervals are found to have been shorter than the updated value by at a least a predetermined amount of time, a rate smoothing function is activated wherein the rate of delivery of stimulating pulses is prevented from changing, from cycle to cycle, by more than a predetermined maximum amount. A peak rate support function preferably employs the same updated value in the computation of "escape" intervals. Following the latest A-A interval, if that A-A interval is less than the updated value, then the updated value is used as the new escape interval.

Abstract: A method of and apparatus for pacing a patient's heart at a pacing rate dependent on patient activity and posture particularly during stair climbing. A dual chamber, rate responsive pacemaker for pacing a patient's heart includes at least one DC accelerometer mounted in the pacemaker pulse generator for implantation such that the sensitive axis of the DC accelerometer is sensitive to the effects of gravity during forward lean of the patient characteristic of stair climbing posture. The DC and AC signal outputs of the accelerometer are processed to develop a tilt signal and an activity signal. A target rate control signal is derived from the activity signal dependent on the level of activity. A stair climbing rate is selected for controlling the physiologic pacing rate between a lower and an upper pacing rate in the presence of an activity signal indicative of a patient walking rate and a tilt signal value falling within a tilt window.

Abstract: A dual chamber pacemaker is provided having capability for adjusting the AV escape interval so as to optimize the timing of delivered ventricular pace pulses for therapy of patients with cardiomyopathy. The pacemaker system continually monitors to determine when a delivered pace pulse results in a fusion beat, and periodically adjusts the AV escape interval in accordance with the percentage or rate of incidence of such fusion beats. In one specific embodiment, the pacing system determines the percentage of delivered ventricular pace pulses which are followed by fusion beats over a predetermined number of intervals, and decrements AV escape interval when such percentage is not below a predetermined minimum. The pacing system also periodically increments AV escape interval when the rate of fusion beats is acceptable, thereby providing a closed loop system for maintaining the AV interval at an optimally long value consistent with maximizing full capture by delivered ventricular pace pulses.

Abstract: New pacing algorithm defines faster than indicated pacing rate during detection of PAC's/PVC's and reduces rate after awhile to a safety rate unless natural depolarizations are detected.

Abstract: A method and apparatus for automatic determination of a pacemaker patient's pacing stimulation threshold. Circuitry is provided in a pacemaker for obtaining a signal reflecting cardiac impedance, which is known to reliably reflect certain aspects of cardiac function. Circuitry is also provided for monitoring the cardiac impedance waveform during a predetermined capture detect window following delivery of stimulating pulses. One or more values are derived which characterize the morphology of the impedance waveform during the capture detect window associated with each stimulation pulse delivered. These values are compared to predetermined control values in order to assess whether a stimulation pulse has achieved cardiac capture. The assessment of whether cardiac capture has been achieved is also based partly upon the conventional sensing of atrial and/or ventricular cardiac signals occurring during the capture detect window.

Abstract: A capture verification system for a cardiac pacemaker comprising an implantable pulse generator (IPG) and one or more pacing leads having a proximal end coupled to the IPG and a distal end in contact with a patient's heart. The capture verification system employs a pressure wave sensor mounted in the IPG in relation to the proximal end of the pacing lead for sensing pressure waves transmitted from the distal end of the pacing lead to the proximal end thereof. The pressure waves include characteristic sounds of heart contraction and/or distal end lead motion caused by the contraction motion of the patient's heart that are transmitted along the lead body to the active sensor. A further isolated, reference sensor is also incorporated into the IPG in a similar fashion. Signal processors are coupled to the pressure wave and reference sensors for nulling out common mode noise.

Abstract: A method and apparatus for cardiac pacing, which provides for delivery of pacing pulses at an increased rate in response to a detected rapid drop in heart rate. A rapid drop may be detected in response to a drop of greater than a defined amount from the highest detected heart rate, over a preceding time period. Alternatively, an unbroken sequence of pacing pulses delivered at a base pacing rate may trigger pacing at an increased pacing rate.

Abstract: A dual chamber, rate-responsive pacemaker for pacing a patient's heart novelly allows tracking of the patient's sinus rate when the sinus rate is slightly less than the sensor rate; i.e., within a predetermined "Sinus Preference Window Maximum Rate Drop." Pacing at the sensor rate occurs when the sensor rate exceeds the sinus rate by more than the Sinus Preference Window Maximum Rate Drop. In the preferred embodiment a Sinus Preference Window, which occurs at the end of the ventricle-to-atrium interval, is decremented with successive heart beats by a programmable delta to increase the pacing rate until the Sinus Preference Window reaches zero, in which case the pacemaker paces at the sensor rate. The Sinus Preference Window is reset to its maximum value upon either the detection of an atrial sensed event, or upon the expiration of a programmable Sinus Check Interval.

Abstract: Because a determination of atrial tachycardia can occur too often where the pacemaker maintained true atrial interval value is designed to converge on the shortest A-A intervals, a method and apparatus either extends PVAB to cover inappropriate atrial senses that should not be counted in determining the true atrial interval, primarily where they occur after an atrial pace, or removes other AS events from consideration.

Abstract: A rate-responsive cardiac pacemaker implements a novel pacing mode, identified as ADIR/VVIR, which is especially effective for patients with Sick Sinus Syndrome and only intermittent atrioventricular block. Within the same pacemaker circuitry, an AAIR pacemaker and a VVI pacemaker (with an escape rate below that of the AAIR pacemaker) are provided with atrial blanking following both atrial and ventricular events. Ventricular blanking after atrial pacing is minimized for better detection of R-waves following an atrial paced event.