Abstract: There is provided a cardiac pacemaker system with a ventricular tachycardia prevention feature, whereby the pacemaker monitors ventricular activity during each patient awakening period to determine when VT is likely. In a preferred embodiment, QRS and T wave templates are generated cyclically during awakening, and compared to normal templates to obtain a measure of variability, indicative of refractory dispersion and thus of probable VT. Ventricular extra-systoles are also monitored and analyzed during the awakening period to see how closely they occur to the ventricular vulnerable period. When the monitored data indicates VT probability during awakening, the pacemaker responds by overdriving the heart with an intervention pacing rate which is continually adjusted as a function of the currently obtained data.

Abstract: There is provided an implantable device system such as a battery-powered pacemaker system, with an improved capability of measuring battery internal impedance, thereby providing the means to determine anticipated device End of Life. Within one pacemaker cycle following a sensed beat or a delivered stimulus, and before delivery of a next stimulus, three battery measurements are taken at equally spaced time intervals. Due to the RC nature of the battery internal impedance, the first two battery voltage measurements can be used to calculate what the voltage would be at the third time, assuming no change in current load. At the third time, a predetermined incremental current load is added, and the battery voltage at the time of the added current load is measured. The voltage differential between the calculated battery voltage and the measured battery voltage at the third time, together with the predetermined incremental current load, is used to calculate the battery impedance.

Abstract: A pacing system and method for determining a heart failure condition such as left ventricular dysfunction in a patient are provided, based upon obtaining information from cardiac signals, which information is processed and examined for an indication of the onset or progression of LVD. Since LVD is generally characterized by conduction disorders and other body responses calling for different heart rates during exercise, an examination of sensed cardiac signals is utilized to obtain data reflective of an LVD condition. In one embodiment, a QT rate responsive pacemaker is utilized, wherein variations in QT interval corresponding to heart rate are detected and stored, and then periodically analyzed to detect changes of sufficient magnitude to indicate onset of LVD. In another embodiment, changes in lower natural rate at nighttime or rest are monitored and analyzed for detection for a trend indicating LVD.

Abstract: There is provided a pacemaker system having the feature of delivering a ventricular safety pulse (VSP) following an early ventricular sense (VS), wherein the pacemaker automatically determines whether VSPs are to be delivered following early VSs, and if yes, with what timing. The pacemaker gathers data following delivered VSPs, which data contains information indicative of whether each early VS was indeed the result of a spontaneous R wave, or was due to crosstalk from a prior delivered atrial pace pulse. This data is processed and, when it presents a high statistical confidence, is used to make a determination of whether to respond with the assumption of a true R wave, or of crosstalk. If the data is not statistically significant, the pacemaker delivers VSPs in a normal fashion, e.g., at the end of a programmable VSP interval timed out following delivery of an atrial pace pulse.

Abstract: A device and method useful in the diagnosis and treatment of congestive heart failure. Specifically the present invention senses the trans-thoracic impedance as well as patient posture. By correlating changes in posture with trans-thoracic impedance changes, the present invention is able to diagnose and assess the degree of congestive heart failure. The present invention is described in the context of an implantable pulse generator system, but it may also be practiced in conjunction with various types of implantable devices.

Abstract: A programmable pacemaker system, having a programmer which has the capability of making software control modifications to a family of pacemakers types which can be software modified with different control functions. The programmer carries manual data relating to the manual corresponding to each pacemaker type. Whenever a new control software release is loaded into the programmer, an accompanying new manual portion is also loaded into programmer memory; the programmer can determine what manual portion or portions are superseded if the new control software is downloaded into any one of the respective different pacemaker types of the family. Whenever a programmer is used to download a new control routine into an implanted pacemaker, the programmer automatically provides the option to display and/or print a new applicable manual portion; superseded manual portions due to downloading operations; and/or the entire manual corresponding to the pacemaker as modified by the downloading operation.

Abstract: A system and method are provided for inducing ventricular tachycardia in a patient to enable testing to determine the optimum parameters for anti-tachycardia stimulation. The implantable device provides for overdrive pacing of the heart for a short sequence, followed by delivery of a series of pulse pairs. Each pulse pair has a first stimulus pulse delivered at the same or similar overdrive rate, and an inducing pulse which is delivered in timed relation to the evoked T-wave, preferably during the falling edge portion of the T-wave. In this way, each cycle the inducing pulse is timed for efficaciously inducing tachycardia. The timing of the inducing pulse is enhanced by near field sensing of the T-wave at about the location where the pulses are delivered, preferably using bipolar sensing and/or sense circuitry designed to recover the signal with an optimum time response.

Abstract: There is provided an implantable cardiac pacing system or other cardiac monitoring system, having an enhanced capability of classifying intracardiac signals through a combination of DSP techniques and software algorithms. The implantable device has one or more DSP channels corresponding to different signals which are being monitored. Each DSP channel provides for amplification of the incoming signal; conversion from analog to digital form; digital filtering of the converted signals to provide filtered signals; operating on the filtered signals to provide slope signals; determining from the filtered and slope signals whenever an intracardiac event has been detected, e.g., R wave, P wave, etc.; and signal processing of the filtered and slope signals for a predetermined analysis interval after threshold crossing, for generating a plurality of signal parameters.

Abstract: There is provided an implantable cardiac pacing system, having multiple sensing channels for sensing spontaneous cardiac signals which arise between respective different pairs of electrodes. In a preferred embodiment, the system utilizes a single pass VDD-type lead, having at least one atrial ring electrode for sensing atrial signals, and at least a distal tip electrode positioned in the right ventricle for sensing ventricular signals. Sensing channels concurrently process signals between the atrial ring and the pacemaker can (the indifferent electrode); the ventricular tip electrode and the pacemaker can; and the between the atrial ring and the ventricular tip. One or more additional electrode pairs can also be employed. Enable signals selectively enable the channels to be used for concurrent processing of the signals.

Abstract: There is provided a pacemaker system with an SRD detection and intervention feature, which enables a simple way of initiating confirmation of SRD, i.e., looking for an AS/AP transition in a DDD or DDI pacemaker, or a transition from a VS to a VP in a DDI pacemaker. This simple initiation of SRD confirmation is made possible by use of a relatively wide hysteresis band which is normally operative when a spontaneous rate is present, and which tracks physiological changes in the patient's natural rate, across the pacemaker rate range. Transitions which result from a gradual decrease in natural rate and thus represent physiological bradycardia are not interpreted as suggesting SRD. The detection is confirmed only after a predetermined number of pace pulses are delivered at the hysteresis rate, i.e., 1-5 pulses.

Abstract: A pacing lead, and system for pacing, where the lead has an improved distal tip designed to provide reliable chronic fixation of the electrode-heart interface, while also providing low pacing threshold. The distal end of the lead has a standard surface, of roughly hemispherical shape, made of a porous material. In one embodiment, the tip surface is suitably about 6-8 square mm, and there is a smaller surface of about 1.5-2.0 square mm which is electrically isolated from the remainder of the porous surface; the smaller surface acts as a high impedance electrode, providing low threshold, while the larger porous surface provides the stable fixation. A steroid source is housed in the distal end of the lead, so as to provide an eluted steroid to the electrode surface area, as well as at least part of the remaining porous surface, whereby the overall porous surface and the eluted steroid minimizes the resulting capsule of non-excitable tissue around the electrode, providing for a stable reduced threshold.

Abstract: There is provided a pacing system having special functions for treating the patient's atrium with atrial pacing so as to reduce the probability of occurrence of dangerous atrial arrhythmias. The pacemaker of the system provides for atrial Pace.sub.-- Conditioning, whereby the patient's normal intrinsic atrial rate is overridden by higher rate pacing whenever a predetermined sequence of intrinsic heartbeats is sensed. The pacemaker also provides for special pacing routines following the detection of one or more PACs. The PAC response routines include pacing at an elevated rate for a predetermined time or number of beats, and smoothing out pacing intervals for one or several cycles following the occurrence of a PAC.

Abstract: There is provided an output stage for a battery powered implantable device, such as a cardiac pacemaker, for generating biphasic or triphasic pulses, each pulse having at least a prestimulus or poststimulus pulse of a first polarity, and a stimulus pulse of opposite polarity. The output stage provides for charging of a small sized pacing capacitor from the battery through a high rate charge pump only during delivery of a prestim or poststim pulse, and for discharging the pacing capacitor during the stimulus portion of the overall pulse. A fast or high rate capacitive charge pump is used with a controllable high rate clock signal, adjustment of the clock signal being used for controlling the charging rate during the prestim or poststim pulses, thereby allowing for tuning of the parameters of the prestim or poststim pulse portions.

Abstract: There is provided a pacing system, preferably a VDD system having a single pass lead with one or two ventricular electrodes and a pair of atrial electrodes. The pacemaker has timing and logic capability for determining when an atrial back-up pulse, such an atrial synchronization pulse, can be delivered, and also whether the pacemaker can provide for continuing atrial pacing. The pacemaker is provided with a plurality of modules for determining the likelihood that a delivered atrial pace pulse resulted in atrial contraction, and for storing data relating to the probable capture or no.sub.-- capture result of each delivered pace pulse. One of the capture-determining modules is a timing module which stores a plurality of rules by which a sequence of events and rates surrounding a delivered atrial pace pulse is analyzed to determine the probability of capture.

Abstract: There is provided an air core antenna, and method of production of same, suitable for use in implantable device, the antenna being used for telemetric communication with an outside programmer unit. The air core antenna is fabricated upon a hybrid substrate, which substrate is subsequently processed to contain electronic circuits for use in the implantable device. A groove is milled into the perimeter side walls of the antenna, and the coil wire is wound within the groove, the two ends of the coil then being attached to connector pads on the substrate. There is thus provided an antenna which is integrally incorporated into the substrate so that space requirements of the antenna are minimized, providing an antenna which has a sufficient loop area to provide the receiving and transmission characteristics required of a modern programmable implanted device.

Abstract: There is provided a pacemaker system and method for enabling special rate control for patients who have specially recognized conditions, e.g., patients who are post-ablation and thus are susceptible to bradycardia-dependent ventricular fibrillation or other arrhythmias. In a preferred embodiment, the pacemaker has a special function rate control algorithm which, for the post-ablation patient, commences pacing with a lower rate limit at a high start value of around 80-100 bpm, and decays the lower rate limit down to an end value of about 60-70 bpm over a duration of about a month. Additionally, the pacemaker is provided with one or more selectable special function rate response algorithms, for enabling higher rate response to patient exercise and demand for increase cardiac output. The combination of the gradual decay of lower rate limit over the programmable duration as well as the specially programmable rate response enables optimization of pacing so as to prevent arrhythmias.

Abstract: There is provided a pacemaker having automatic adjustment of the sensitivity for sensing cardiac signals such as QRS, T and P waves. The pacemaker has software for examining each inputted signal, obtaining a measure of the peak amplitude, e.g. one-half, comparing such measure with a stored software sensitivity level, and adjusting the software sensitivity level each beat so that it effectively tracks beat-to-beat changes in the signal amplitude. The adjusted software sensitivity level is used for determining when an input signal is to be accepted as a true signal, or rejected.

Abstract: There is provided a cardiac pacing system for dealing with dangerous atrial arrhythmias, wherein when an episode of such an arrhythmia is detected, the system operates to cool the A-V node so as to reversibly block conduction of the atrial excitations through to the ventricle, permitting uninterrupted asynchronous ventricular pacing during the episode. The system provides for an atrial lead having a Peltier element positioned toward its distal end, such that when the atrial lead distal end is affixed to the atrial heart wall, the cooling element is proximate to the A-V node. Upon detection of a dangerous atrial episode, the Peltier element is energized to cool the A-V node to point of effective block, and the pacemaker switches to asynchronous pacing.

Abstract: There is provided an implanted pacemaker having a system and method for determining a measure of the circadian rhythm of a patient and adjusting the pacemaker nighttime setting of lower rate limit to correspond to the determined circadian rhythm. In a preferred embodiment, the circadian rhythm is determined by examining daily variations in QT interval. In a first QT embodiment of the invention, when QT interval becomes longer than a parameter QT.sub.-- sleep, which represents a value associated with patient nighttime, the LRL is dropped to a night value and maintained at such value for a predetermined duration. In another embodiment, the start of night LRL is determined as a function of when QT interval becomes longer than a sleep value for a predetermined elapsed time, and LRL is changed back to a day value when QT interval drops back down to a shorter value than the sleep value and stays there for an elapsed period of time.

Abstract: A pacemaker system is provided which provides for more flexibility in re-programming of the control software, or program which is controlling an implanted pacemaker. The system comprises an external programmer device which is capable both of programming the implanted device in a conventional way, and also downloading new control software to the implanted device, subject to predetermined system conditions. All implanted devices, e.g., pacemakers within the system of the invention, share a hardware platform, and are identified as belonging to a given one of a plurality of groups, each group being characterized as providing therapy aimed at a different condition. Each pacemaker also carries type data, indicating the type of pacemaker within the group, and a set of permissions data representative of different types within the group to which it is permitted to be programmed.