Abstract: Techniques for stabilizing the rate of a ventricle, during conducted atrial fibrillation for example, adjust the escape interval of an implantable medical device to increase or decrease the pacing rate. In some embodiments, the escape interval is adjusted to achieve and maintain a percentage of pacing. In other embodiments, the stability of the ventricular rate is quantified as a function of measured R-R intervals, and the escape interval is adjusted to achieve and maintain a level of stability. In still other embodiments, a mean compensatory pause length is determined, and the escape interval is adjusted as a function of the mean compensatory pause length, to maintain the escape interval at or near the mean compensatory pause length.

Abstract: An apparatus and method for detecting respiratory disturbances based on multiple physiological parameters are provided. The method includes sensing one or more physiological signals, deriving from the sensed signals multiple physiological parameters that change during a respiratory disturbance, computing a probability that the respiratory disturbance is present using the multiple physiological parameters, and detecting the respiratory disturbance if the probability exceeds a predetermined threshold. In some embodiments, the method further includes generating an alert signal or other report in response to a respiratory disturbance detection. In other embodiments, the method further includes triggering the delivery of a therapy in response to a respiratory disturbance detection.

Abstract: An implantable medical device operates to promote intrinsic ventricular depolarization according to a pacing protocol. When a cardiac rate exceeds a predetermined threshold, the implantable medical device modifies the pacing protocol parameters to promote AV synchrony.

Abstract: An implantable medical device operates to promote intrinsic ventricular depolarization according to a pacing protocol. The medical device operates to promote intrinsic conduction by providing elongated AV intervals or operating in an atrial based pacing mode. Conduction checks to determine if AV conduction is present are performed on a graduated or progressive scale to facilitate intrinsic emergence.

Abstract: An implantable medical device operates to promote intrinsic ventricular depolarization according to a pacing protocol. The medical device monitors the number of attempts made to promote intrinsic conduction in comparison with the number of successful cardiac cycles to determine an efficiency value.

Abstract: An implantable medical device operates to promote intrinsic ventricular depolarization according to a pacing protocol. The medical device monitors the AV interval and adjusts the Ventricular Pacing Protocol if the AV interval exceeds a threshold when the cardiac rate is elevated.

Abstract: An implantable medical device operates to promote intrinsic ventricular depolarization according to a pacing protocol. The medical device determines a course of action based upon the presence or absence of sensed ventricular activity. The device further determines whether that activity is properly conducted or the result of a PVC or nodal rhythm.

Abstract: A Ventricular Pacing Protocol (VPP) is provided that reduces ventricular pacing. The VPP has varying levels of aggressiveness that are more or less tolerant of an absence of intrinsic ventricular activity within a given interval. During periods of sleep, the VPP is adjusted to a more aggressive level to further reduce ventricular pacing based upon the reduced hemodynamic requirements of a patient during sleep.

Abstract: An implantable medical device identifies onset and/or progression of left ventricular dysfunction (LVD). The implantable medical device receives a signal that represents electrical activity within a heart, e.g., an electrogram signal, and digitally processes the signal to assess left ventricular function. In particular, the implantable medical device measures at least one characteristic of QRS complexes within the signal, and assesses left ventricular function based on measurements. The implantable medical device may, for example, measure the width of the QRS complexes and/or the amplitude of the R-waves within the QRS complexes. The implantable medical device may alert a patient or clinician of the onset or progression of LVD, and may control delivery of therapies, such as rate-responsive pacing and cardiac resynchronization pacing, based on the measurements. The implantable medical device may also control delivery of a drug by an implanted drug delivery device, e.g., drug pump, based on the measurements.

Abstract: A method of pacing cardiac tissue using an implantable medical device is provided. A first fibrillation-indicative interval is determined based on a first fibrillation-indicative event. A first adjusted pacing interval, wherein the first adjusted pacing interval is shorter than the first fibrillation-indicative interval, is determined and the cardiac tissue is paced based on the first adjusted pacing interval. If the cardiac tissue is not captured by pacing at the first adjusted pacing interval, an additional fibrillation-indicative interval is determined based on an additional earlier fibrillation-indicative event. An additional adjusted pacing interval, wherein the additional adjusted pacing interval is shorter than the additional fibrillation-indicative interval is determined and the cardiac tissue is paced based on the additional adjusted pacing interval.

Abstract: A method of measuring a source impedance of at least one cardiac electrical signal in a mammalian heart is provided. A first amplifier system is operated. A first signal from a chamber of the heart is received. The first signal is passed through a first amplifier. A second amplifier system is then operated. A second signal from the chamber of the heart is received. The second signal is passed through a second amplifier. Finally, the source impedance of at least one cardiac electrical signal is calculated. The source impedance is based on the amplified first signal and the amplified second signal.

Abstract: A method of operating an implantable medical device is provided. A plurality of atrio-ventricular (AV) measurement signals is received. A QT interval is determined. The QT interval is a function of the AV measurement signals. Each of the plurality of AV measurement signals is compared with the QT interval. Finally, if one of the plurality of AV measurement signals is less than the QT interval, a difference between the one of the plurality of AV measurement signals and the QT interval is stored.

Abstract: A method for instantaneously stimulating a mammalian heart is provided. The mammalian heart includes a first atrium and a second atrium. A commencement signal is received. At least one additional signal is received. A plurality of intervals corresponding to the time between two successive signals is measured. An average interval is calculated. One of the plurality of intervals is compared to the average interval. Finally, a contraction signal is instantly transmitted to the second atrium when a difference between the average interval and one of the plurality of intervals is greater than a predetermined time period, instantaneously transmitting a contraction signal to the second atrium.

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: A dual chamber pacemaker for providing ventricular pace pulses synchronized with atrial senses or paces, and having specific control for optimizing the AV escape interval and resultant AV delay for purposes of therapy for a patient with hypertrophic obstructive cardiomyopathy (HOCM). The pacemaker has an algorithm for varying the AV escape interval and detecting when the AV delay is lengthened to the point of evoking a fusion beat, thereby providing an accurate indication of a patient's underlying PR interval without significant loss of pacing capture. By monitoring T-wave detection and drop in amplitude of the evoked T-wave, an algorithm is enabled for optimizing the pacemaker AV delay within a range of values just less than the longest value for obtaining pre-excitation by the delivered pace pulse.

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 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: A biomedical system such as a pacemaker system having an implantable pacemaker and external apparatus, with communications capability for communicating between the implanted device and the external apparatus, characterized by the implanted device having means for cyclically transmitting event and device timing data representative of each prior device interval, the external apparatus having means for receiving and storing the data and for graphically constructing a graphic output representative of the timing and event information over a plurality of device cycles. Graphic output preferably includes a linear timing graph representative of timing functions of the implanted device.

Abstract: A pacemaker system incorporates an implantable pacemaker and a plurality of electrodes, electrodes preferably being on a pacing lead for a single chamber pacemaker, or a pair of such leads for a dual chamber pacemaker. Programmable connection means are provided for connecting the pacemaker output to a selected combination of lead electrodes, the selection being changed during each pacer cycle to optimize the choice of unipolar and bipolar operation for given pacemaker events. In one mode, the system employs bipolar QRS sensing and unipolar pacing and T-wave sensing. In another mode, the system employs bipolar QRS sensing and pacing, and unipolar T-wave sensing.

Abstract: A dual chamber pacemaker having means for operating in different pacing modes, including dual chamber modes, contains the capability of switching into a fixed rate ventricular pacing mode and of sensing early atrial signals without affecting the ventricular pacing timing. The timing of a plurality of such sensed early atrial signals is analyzed to determine if they represent retrograde P waves and, if so, the indicated V-A conduction time. The pacemaker atrial refractory time is adjusted so that, during dual chamber operation, the atrial refractory time extends past the time of anticipated retrograde P waves, thereby optimizing the setting of the atrial refractory period for avoidance of pacemaker mediated tachycardia. Other pacing conditions may also be adjusted in response to the determined patient V-A time.