Abstract: A VDD-type pacing system which may have a floating atrial electrode analyzes P-wave events and absences of P-waves to determine data indicative of the likelihood of P-wave undersensing. The pacemaker logic chooses a reaction algorithm to respond to atrial events in accordance with whether an absence of a P-wave is more likely to have been an undersense or an incidence of bradycardia. Specific algorithms are presented which illustrate pacemaker reactions to probable undersense and brady occurrences. The pacemaker also incorporates a subsystem for detection of undersense events.

Abstract: There is disclosed a pacemaker, a dual chamber VDD(R) or DDD(R) pacemaker, having improved features for avoiding undesired sensor-sinus competition and providing blended sensor and sinus (atrial) control. The pacemaker employs atrial hysteresis which is used during sensing of natural atrial beats in order to enable tracking the sinus signals that occur at rates below the current pacing limit; and sensor hysteresis which prevents early takeover by sensor control and, in a DDDR pacer, controls when the sensor rate controls over a sensed sinus rate and also enables dropping the pacing rate during sensor control so as to enable finding and tracking of underlying lower rate sinus signals. The sensor hysteresis function is automatically adapted by obtaining and processing scattergram data representative of the sensor rate compared to the average of the natural sinus rate, and adjusting the sensor hysteresis function to optimally match the data.

Abstract: A rate adaptive pacemaker and method of operation, where the sensor-indicated rate is adjusted as a function of sensed sinus rate. The pacemaker is particularly adapted for VDDR operation. The natural sinus rate is compared to the sensor-indicated rate at one or more rates, and the sensor response function is adjusted, or adapted as a function of such comparisons, so as to optimize sensing of the atrial rate and maintenance of synchronous operation. The rate response function may be adjusted specifically at upper pacing limit, and may also be adjusted as a function of comparisons made at other rates.

Abstract: The dual chamber system and method of operation contains an automatic test for determining an optimum AV interval at a test frequency such as LRL. In a preferred embodiment the test is carried out at nighttime, wherein the implanted pacer is set to asynchronous operation at LRL, and AV interval is sequenced through a range from a predetermined AV.sub.min to a predetermined AV.sub.max. The QT interval corresponding to each respective AV interval is determined and stored; the QT data is analyzed to determine the maximum QT interval; and the optimum AV is determined at that which corresponds to the maximum QT. The optimum AV interval thus found is incorporated into the pacer memory for use in timing out AV interval. The optimum AV data may be utilized for determining AV=f.sub.s (rate) for calculating AV interval following each AS, as well as AV=f.sub.p (rate) for calculating AV interval following an atrial pace.

Abstract: A pacemaker for providing optimized inhibit and trigger responses, operating in a VVD or AAD mode. For each pacemaker cycle, the pacemaker is controlled to time out a refractory interval, an inhibit interval or range following a refractory interval, and a trigger interval or range which follows the inhibit interval and ends at the time out of the scheduled escape interval. A signal sensed during the inhibit range results in no pace pulse delivery, the pacemaker goes to the trigger mode and extends the escape interval. Any signal thereafter sensed before the time out of the extended escape interval results in delivery of a trigger pulse and restarting of a new pacemaker cycle. If no signal is sensed during the inhibit range, any signal sensed during the trigger range results in generation of a trigger pulse and the start of a new pacemaker cycle.

Abstract: A system and method are provided for accurate determination of various tremors and movements derived from Parkinson's Disease and other causes. Movement signals are generated by an accelerometer, the movement signals being analyzed to determine whether they are in a predetermined frequency range, and when there occurs an uninterrupted series of such movement signals that are within the frequency range. By determining when these two criteria are met, tremor signals are reliably discriminated from other activity signals. The system includes circuitry for collecting and storing data concerning the timing of tremor occurrences, the timing of other activity occurrences, and amplitude data concerning tremor occurrences.

Abstract: A dual chamber pacemaker system is provided having means for determining when sensed atrial signals have a physiological rate, and tracking only such sensed atrial signals as are found to have physiological rates. The pacemaker provides logic means for continuously determining a physiological rate as a function of sensed atrial rate, whereby physiological rate substantially tracks the rate of sensed physiological atrial signals. The pacemaker also determines dynamic decision rates which are coupled to follow the physiological rate. The decision rates comprise a dynamic pacing limit, which sets the pacing escape interval; a dynamic tracking limit, which sets the upper limit of the physiological range of rates which are tracked; and the dynamic Wenckebach limit, which defines the upper rate for a dynamic Wenckebach range.

Abstract: A dual chamber pacemaker is provided having incorporated therein a VA conduction test for concurrently testing for the conditions of retrograde conduction (RC) and far field R wave sensing (FFRS). The pacemaker changes the AV or VV interval to a predetermined interval over a number of pacemaker cycles, and determines whether the VA interval remains substantially unchanged, i.e., the VA intervals are substantially equal. When VA interval equality is determined, the pacemaker checks the measure of VA interval with stored RC and FFRS criteria to determine whether either can be verified. Respective corrective steps are taken if either RC or FFRS is verified.

Abstract: A pacing lead is disclosed having folded tine elements in a first normal state, the tine elements being adapted to be unfolded by insertion of a stylet. In the second unfolded state, the tine elements are stretched to conform closely to the outer diameter of the lead casing, providing a reduced cross-section that facilitates introduction of the lead, and repositioning of the lead tip. A telescoping arrangement of inner and outer tubing elements is used to enable the stretching of the tine elements.

Abstract: A pacemaker system and method for predicting cardiac allograft rejection noninvasively through the analysis of the T-wave amplitudes of evoked heartbeats. A pacemaker suitable for detecting the T-wave portions of heartbeat signals, such as the Rhythmyx pacemaker, is utilized for providing T-wave information, preferably the amplitude of the T-wave, which information is analyzed for determining a trend indicative of rejection. A decrease, or diminution of evoked T-wave amplitude indicates rejection, and can be used for appropriate follow-up treatment.

Abstract: A dual chamber pacemaker is provided having a connector of reduced width, enabling an overall thinner pacemaker case. The connector receives dual chamber leads and each pair of connector blocks corresponding to a respective one of the leads is tilted toward the center of the connector by a predetermined angle, e.g. about 6.degree.. The tilt angle enables a thinner connector, and thus a thinner pacemaker case, while providing distinguishable axis points at the top of the connector.

Abstract: There is provided a pacemaker lead for use in a dual chamber pacemaker system, wherein the single lead provides for ventricular pacing and atrial sensing. The lead has at least two floating bipoles positioned for placement in the atrium. A first whole-ring bipole is positioned a distance from the distal end so as to be positioned in the lower atrium of an average patient when the distal end is in position for ventricular pacing, and a second split-ring bipole is placed on the lead proximal from the first bipole so as to be positioned in the upper atrium of the normal patient. The method thus comprises positioning a floating whole-ring bipole in the lower atrium, and/or positioning a floating split-ring bipole in the upper atrium. The pair of bipoles so placed provide for atrial sensing with a high degree of ventricular far-field rejection, enabling VDD pacing and also monitoring of P-wave direction and conduction duration.

Abstract: A pacing system and method for delivering atrial stimulus pulses is provided, wherein detected AV interval is utilized for increasing or decreasing atrial pacing interval. The AV interval is compared with an AV reference value each cycle to determine direction of change of pacing, the AV reference being updated each cycle in accordance with a predetermined correlation of change of pacing interval and change of AV reference. The pacing system may be either DDDR or AAIR. In the AAIR embodiment, a single atrial lead is used and the far field ventricular R wave signal is sensed from the total electrocardiogram signal obtained from the atrial lead.

Abstract: A pacemaker system is provided for rate responsive pacing, wherein rate is controlled as a function of two or more sensor inputs, each sensor providing a signal representing a respective different control parameter. Preferably a first sensor signal represents a physiologically accurate although slow response signal such as OT interval, and a second sensor represents a relatively fast response such as activity. The two parameter signals are processed so that they are directly comparable and can be compared as indicators of pacing rate throughout the desired pacing range. The algorithm utilizes a parameter control reference curve for each respective parameter, such reference curve representing the desired correlation between pacing rate and the parameter signal.

Abstract: A rate adaptive pacemaker system, and method of operation, is provided which has a pacemaker which generates pacing pulses at a controlled pacing rate as a function of at least one monitored patient variable. The correlation of pacing rate with the patient variable is nonlinear, or dynamic, and is adapted to actual patient conditions. The value of the relationship between the pacing rate and the monitoring variable is determined at the lower rate limit and the upper rate limit, and the dynamic characteristic between these limits is automatically adjusted.

Abstract: There is provided an endocardial pacing lead having a substantially cylindrical length and an electrode at about the distal end thereof, the lead having a conductor for conducting signals between the proximal and distal ends thereof and an outer tubing enclosing the conductor for substantially the length of the lead. A tined piece is provided which envelopes the lead tubing just proximal to the distal electrode, the tined piece having a plurality of tines, each such tine being formed with a substantially C-shaped cross-section having its inner or backward surface substantially complementary to the outer surface of the tubing. The tined piece also preferably provides riser elements interspaced between respective pairs of the tines for providing a raised lead surface adjacent the tine interangles, thereby increasing the effective tined inter-radius presented to heart wall structures.

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 physiological device adapted for implantation in a human patient, e.g. a cardiac pacemaker or muscle stimulator, characterized by having programmable means for generating data and assembling same for presentation of one or more histograms. The implanted device has circuitry for registering the occurrence of sensed or evoked events, as well as device operating events such as cycles of operation, and means, preferably software control of a microprocessor, for classifying registered events into respective classes of one or more parameters associated with the events and for accumulating counts of events for each such class. The system also includes external apparatus for communicating programmed instructions to the device, whereby histogram selection and histogram classes are programmed, and for receiving the histogram data transmitted from the implanted device and displaying it in a convenient histogram form. Time based histograms are also generated, utilizing a software clock for continuously tracking time.

Abstract: A programmable pacemaker apparatus having a microprocessor and means for receiving program information from an external source, means for generating and delivering stimulus signals and means for sensing the occurrence of natural heartbeats in a patient, and having a battery source powering the apparatus, said microprocessor being combined with program instructions stored in memory for controlling the operation of said pacemaker, comprising controller circuit means external to said microprocessor and interconnected therewith for controlling the operating state of said microprocessor, said controller means having occurrence means for determining the occurrence of given events. The controller means further comprises means for stopping operation of the microprocessor on command from the microprocessor and for starting operation of the microprocessor upon determination of one of said events, whereby the microprocessor normally is on less than about 25% of the time.

Abstract: An improved automatically rate adaptive pacemaker, wherein the rate of delivered stimulus pulses is controlled as a function of sensed hearbeat characteristics and/or patient threshold. The pacemaker analyzes different characteristics or parameters of the detected heartbeat signal, and the rate of delivered stimulus pulses is controlled as a function of predetermined correlation factors. The pacemaker includes means for automatic threshold tracking, and also for adjusting the rate of delivered stimulus pulses as a continuous function of the patient threshold.