Siemens-pacesetter, Inc.

Pacesetter, Inc.

James L Duncan

Jason A Sholder

Paul A Levine

Andrew E Epstein

James D Causey, Iii

Bruce L Wilkoff

Werner Hafelfinger

Murray P King

Raymond A Kristall

An antitachycardia stimulation device that automatically adjusts its detection rate threshold as a function of a sensed physiological parameter indicative of cardiac rate. The implantable antitachycardia stimulation device includes heart rate detection circuitry and antitachycardia therapy circuitry for applying a specific antitachycardia therapy in the event that the detected heart rate falls within at least one tachycardia rate zone. The tachycardia rate zone is defined by a lower threshold limit, and may also be defined by an upper threshold limit if more than one rate zone is used. The lower threshold limit is automatically adjusted as a function of an independently sensed physiological parameter that predicts a normal or natural change in the heart rate. If more then one rate zone is used, other threshold limits may also be adjusted automatically as a separate function of the same sensed physiological parameter. In one embodiment of the invention, the implantable stimulation device comprises a rate-responsive pacemaker, and the sensed physiological parameter used to adjust the rate threshold limit(s) is also used to define a sensor indicated rate signal to control the pacing rate of the pacemaker.

Automatic adjustment of detection rate threshold in an implantable

Improved methods and apparatus are provided for applying atrial and ventricular therapies to the heart of a patient using an implanted cardiac stimulating device. Atrial and ventricular heart rates are monitored and analyzed to determine whether the patient is suffering from an atrial or ventricular arrhythmia and to determine what type of therapy is appropriate to apply to the heart. Atrial and ventricular heart rates are compared to determine if the ventricular heart rate exceeds the atrial heart rate and to determine whether the ventricular heart Fate is stable. An early atrial stimulation pulse can also be applied to determine whether the ventricular heart rate follows the atrial heart rate. Atrial and ventricular therapies are applied to the heart based on these determinations.

System and method for discriminating between atrial and ventricular

An implantable cardioversion shock therapy system is provided which delays delivery of a cardioversion shock until late in the cardiac cycle to optimize the chance for the vast majority of ventricular myocardial tissue to be non-refractory. The system in intended to increase efficacy and safety by properly synchronizing the cardioversion shock to the appropriate portion of the cardiac cycle to successfully terminate a tachycardia episode. The timing of the cardioversion shock is programmable as either a percentage of measured tachycardia cycle length or fixed delay in milliseconds.

Implantable cardiac stimulating device and method for administering

A programming system is provided that allows a physician or medical personnel to optimize the settings of various arrhythmia detection criteria and/or parameters related to hemodynamic performance to be programmed into the implanted cardiac stimulating device. The cardiac stimulating device may be a pacemaker or cardioverter/defibrillator that detects heart arrhythmias by using various arrhythmia detection criteria. The cardiac stimulating device is capable of recording the patient's cardiac signals and/or sensor data. The programming system may play back the recorded signals to test the detection criteria and hemodynamic performance and may simulate the response of the device to the cardiac signal. Alternatively, the programming system may play back an artificially created or previously stored cardiac signal for test purposes. As a result, the recorded signal may be played back repeatedly without unnecessarily stressing the patient's heart. Additionally, the programmer may suggest specific arrhythmia detection criteria and therapies to a physician based on an analysis of a patient's arrhythmia.

Programming system having means for recording and analyzing a patient's

A rate-responsive pacemaker includes programmable hysteresis means for automatically extending an escape interval, EI.sub.0, in the presence of sensed intrinsic cardiac activity, and returning the escape interval to its initial value in the presence of pacemaker-stimulated (paced) cardiac activity. The escape interval sets the rate at which stimulation pulses are generated on demand in the absence of sensed intrinsic cardiac activity. The initial value of the escape interval is selected to be the lessor of: (a) a programmed escape interval (determined from a minimum programmed rate), or (b) a sensor-indicated escape interval (determined from a physiological or metabolic sensor used as part of the rate-responsive pacemaker). In addition to the hysteresis mode, a scan mode is optionally provided wherein the escape interval, EI.sub.0, is gradually extended (lengthened) in small incremental steps if no intrinsic activity is sensed during the prior escape interval. In this manner, the pacemaker incrementally 'scans' through an increasingly longer window of time looking for the occurrence of intrinsic cardiac activity before generating a stimulation pulse. A hysteresis rate adjust (HRA) mode is also optionally provided wherein the escape interval is gradually returned to EI.sub.0 over several pacing cycles, rather than abruptly returning to EI.sub.0 in a single step after the hysteresis mode has been ended due to no sensed intrinsic activity during the hysteresis escape interval EI.sub.H.

Hysteresis in a rate-responsive pacemaker

A system and method for preventing atrial competition during sensor-driven operation of a dual-chamber pacemaker includes means for sensing atrial activity during an atrial refractory period. Atrial competition is avoided by either: (1) generating an atrial competition prevention (ACP) interval upon the detection of any atrial activity during the relative refractory portion of an atrial refractory period, and preventing any atrial stimulation pulses from being generated for the duration of such ACP interval; or (2) shortening the atrial refractory period in the event that the sensor-driven rate of the pacemaker begins to approach a rate that might place atrial stimulation pulses near the end of the unshortened atrial refractory period. Further, the invention includes features that allow monitoring of the intrinsic atrial rate to determine if such is much greater than the sensor-driven rate, and, if so: (1) reducing the maximum tracking rate of the pacemaker, and/or (2) switching the operating mode of the pacemaker from a dual-chamber sensor-driven mode to an single-chamber sensor-driven mode.

System and method for selecting a mode of operation of a dual-chamber

System and method for preventing atrial competition during sensor-driven

A system and method for terminating a cardiac arrhythmia includes pacing means for stimulating the heart with at least one stimulation pulse during a narrow region of susceptibility (termination window) of the arrhythmia cycle. The location of the region of susceptibility is initially found by delivering the stimulation pulse(s) to the heart in accordance with a prescribed scan pattern. The scan pattern delivers the stimulation pulse(s) at a time during the cardiac cycle such that each successive stimulation pulse is presented to the heart at a slightly different time than was a prior stimulation pulse, thereby assuring that the region of susceptibility or termination window is eventually located. When the arrhythmia is successfully terminated, the location of the successful stimulation pulse within the prescribed scan pattern is stored. Upon the next occurrence of a cardiac arrhythmia, the initial stimulation pulse is presented to the heart at a time within the prescribed scan pattern that is backed up from the location of the prior successful stimulation pulse by a prescribed amount. Thus, even though the region of susceptibility may have moved in either direction within the cardiac cycle, the initial stimulation pulse of the next scanning sequence is likely to be applied at a location within the cardiac cycle that is near and moving towards the region of susceptibility.

Pacing system for termination of cardiac arrhythmias utilizing scanning

An implantable pacemaker provides a paced AV delay that is automatically adjusted to include patient variations in latency conduction, that is, the time interval between a stimulus to the heart and an evoked potential, time due to lead position and specific patient latency. An AV timer, designed to provide a programmed AV interval, starts its timing operation at the generation of an atrial pulse, and restarts the timing operation again at the occurrence of the evoked atrial potential. The evoked atrial potential is typically monitored from a ring electrode of a bipolar lead relative to the pacemaker can (case), although other monitoring configurations are also possible. The length of the AV intrval is programmed to a desired value using conventional programming techniques. By starting the AV timer from the paced atrial stimulus, and restarting it from the evoked atrial potential, all variablility in nodal conduction time due to lead position and specific patient latency is removed, thereby obviating the need of having the pacemaker make adjustments to the AV interval. The paced AV delay (the time interval from the generation of an atrial stimulus to the generation of a ventricular stimulus) is automatically adjusted to compensate for these variations, while the AV interval (desired time from an atrial depolarization to a ventricular depolarization) remains at the desired value. In a rate-responsive packemaker, the programmed AV interval may still be shortened to mimic decreases in AV nodal conduction during periods of physical activity without affecting operation of the invention.

System and method for automatically compensating for latency conduction

An implantable pacemaker having a unipolar/bipolar lead interchangeability includes lead impedance measuring capability for automatically measuring lead impedance, initiated by the occurrence of predetermined events, such as whenever a programming change is made, whenever capture fails to occur in response to an applied stimulation pulse, whenever the leads are changed, and whenever a significant change of lead impedance is otherwise detected. If a proper impedance measurement is not sensed for a programmed configuration, additional impedance measurements for other possible configurations are made in an ordered sequence in order to determine if an improper lead has been implanted or if a electrode has broken. If an operable configuration is found, signified by a measurement of impedance as expected, the pacemaker continues operation in that configuration, thereby assuring that capture can continue to occur until such time as the problem which has been detected can be corrected.

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Alpharetta, GA, United States of America

James L Duncan