Abstract: A method for sensing cardiac activity in an atrium of a patient's heart includes delivering a pulse to the atrium using an electrode configuration that includes at least a cathode electrode; sensing cardiac activity in the atrium using a unipolar electrode configuration to provide a sensed signal wherein the unipolar electrode configuration does not include the cathode electrode; determining the duration during which the voltage of the sensed signal falls below a threshold voltage; and comparing the determined duration to a parameter to determine whether the pulse caused an atrial evoked response.

Abstract: An implantable medical device includes a lead, a pulse generator, an autocapture module, an autothreshold module, a fusion detection module, and a control module. The lead includes electrodes configured to be positioned within a heart. At least one of the electrodes is capable of sensing cardiac signals. The pulse generator delivers a stimulus pulse through at least one of the electrodes. The autocapture module senses an evoked response of the heart after delivery of the stimulus pulse when operating in an autocapture mode. The autothreshold module performs a threshold search when operating in an autothreshold mode. The fusion detection module identifies fusion-based behavior in the heart. The control module automatically switches between the autothreshold and autocapture modes based on a presence of the fusion-based behavior.

Abstract: An implantable medical device includes a lead, a pulse generator, an autothreshold module and a control module. The lead includes electrodes positioned within a heart. At least one of the electrodes senses cardiac signals. The pulse generator delivers a stimulus pulse through at least one of the electrodes. The autothreshold module performs a threshold search when operating in an autothreshold mode and causes atrial stimulus pulses to be delivered in an atrium of the heart at an overdrive rate during the threshold search. The control module determines an AV conduction time and applies an overdrive AV adjustment to the AV conduction time to generate an AV delay. The autothreshold module uses the AV delay in connection with delivering ventricular stimulus pulses to a ventricle of the heart.

Abstract: A plurality of electrodes are implanted in, on or near the patient's heart and initially configured to define first circuits or vectors enabled for at least one of sensing and stimulating and second circuits or vectors which are idle for at least one of sensing and stimulating. Selected first circuits or second circuits are tested for fault indications related to one or both of sensing and stimulating and a status record is updated to indicate corresponding sensing fault indications and stimulating fault indications. If a sensing fault is found in one of the first circuits, the first circuit is redefined when enabled for sensing to include at least one electrode of a second circuit that does not have a record of a sensing fault indication. Likewise, if a stimulating fault is found in one of the first circuits, the first circuit is redefined when enabled for stimulating to include at least one electrode of a second circuit that does not have a record of a stimulating fault indication.

Abstract: An implantable cardiac stimulation device selects an arrhythmia therapy based upon the time of day. The device comprises an arrhythmia detector that detects an accelerated arrhythmia of a heart, and a data circuit that maintains a time record of cardiac cycle lengths developed during detected accelerated arrhythmias. A therapy circuit provides a selected therapy to the heart based upon the maintained time record of cardiac cycle lengths and the time of day.

Abstract: A pulse is delivered to the atrium using an electrode configuration that includes at least a pulse cathode electrode. Cardiac activity in the atrium is sensed using a unipolar electrode configuration to provide a sensed signal wherein the unipolar electrode configuration does not include the pulse cathode electrode. A determination as to whether the pulse caused an atrial evoked response is made based on a maximum derivative value of the sensed signal with respect to time, a comparison of the sensed signal to a parameter or an integral of the sensed signal with respect to time.

Abstract: An implantable cardiac stimulation device applies pacing stimulation pulses to a heart and senses evoked responses to the pacing stimulation pulses. A pulse generator applies the stimulation pacing pulses to the heart in accordance with a pacing configuration. A sensor control selects an evoked response sensing electrode configuration from among a plurality of evoked response sensing electrode configurations in response to the pacing configuration. A sensor is then programmed to sense the evoked responses with the selected evoked response sensing electrode configuration. In accordance with a preferred embodiment, signal-to-noise ratios obtained with the various electrode configurations are used to select a best electrode configuration for sensing evoked responses.

Abstract: An implantable stimulation device delivers a stimulation pulse in a chamber of a patient's heart and perform periodic threshold tests for generating a statistical model of the threshold data, to minimize the number of threshold tests required over a given time. Based on this statistical model, the stimulation pulse energy is automatically adjusted to a level that minimizes the risk of loss of capture. The autocapture safety margin is determined by the variability of the threshold data accumulated over time such that a minimum safety margin can be set to ensure that the delivered pulse energy always exceeds the threshold level. The timing of the trigger events is continuously adjusted to be proportional to the variability of the threshold data. If the standard deviation of the threshold measurements increases, the trigger would occur more often. If the standard deviation decreases, the trigger would be adjusted automatically to occur less often.

Abstract: Techniques for providing capture verification during overdrive pacing are described. If an overdrive pacing pulse fails to evoke capture (i.e. a loss of capture occurs), a high voltage backup pulse is automatically delivered. Once a second loss of capture occurs during a single sequence of overdrive pacing pulses, an overdrive pulse capture threshold detection search, described herein, is performed while overdrive pacing continues. Various techniques for providing rate recovery are also described herein. The rate recovery techniques are designed to avoid problems that might arise from possible fusion of intrinsic beats and overdrive pacing pulses that fail to evoke capture. In a first rate recovery technique, capture detection is suspended during rate recovery due to the possibility of fusion. Instead, an extra safety margin is added to the overdrive pulses.

Abstract: An implantable stimulation device delivers a stimulation pulse in the ventricular chamber of a patient's heart and automatically adjusts a post-ventricular atrial blanking period. The stimulation device generates a ventricular stimulation pulse to trigger an evoked response, in order to produce a ventricular far-field signal that follows a successfully captured ventricular stimulation pulse. The stimulation device further includes an atrial sense circuit that senses the ventricular far-field signal, and a control system that adaptively segments the post-ventricular atrial blanking period in a post-ventricular atrial blanking period (PVAB) which is fixed in duration, and a variable far-field interval (FFI) window.

Abstract: Optimization of evoked response detection in an automatic capture detection system employed by an implantable cardiac stimulation device is presented. Patient state information is used to determine the appropriate settings of variables that are associated with the evoked response signal detection algorithm. The variables used by the evoked response signal detection algorithm are first established for the patient in a variety of positions. During operation of the implantable cardiac stimulation device, the patient state is monitored and the variables used by the evoked response signal detection algorithm are adjusted accordingly.

Abstract: An apparatus and method for operating an implantable stimulation device are disclosed. The implantable stimulation device is configured to dynamically modify pacing pulse energies based upon a patient's varying capture threshold. In at least certain situations where the implantable stimulation device modifies the pacing pulse energy, a stored value for an operating parameter, such as a ventricular blanking period or a maximum sensor rate, is automatically adjusted based upon the new pacing pulse energy. Additionally, the stored value may also be adjusted by additional variables in combination with the new pacing pulse energy.

Abstract: An implantable cardiac stimulation device establishes communication with at least first and second external devices which communicate using first and second communication protocols, respectively, and wherein the first and second protocols are different. The implantable device includes a pulse generator configured to generate stimulation pulses and a telemetry circuit arranged to establish communication with the first and second external devices according to the first and second communication protocols, respectively. A control circuit coupled to the telemetry circuit and the pulse generator detects the first and second external devices based upon the protocol used in establishing communication to provide a first response when the first external device is detected and a second response when the second external device is detected.

Abstract: A multi-chamber stimulation device and associated method reliably and automatically distinguish fusion from loss of capture during ventricular stimulation. The stimulation device provides immediate and accurate fusion detection when a loss of capture is suspected in the ventricles without delivering back-up stimulation pulses. To achieve this objective, the far-field signal present in the atrial channel is examined for evidence of a far-field R-wave whenever the ventricular channel detects a loss of capture. If a far-field R-wave is present, fusion is confirmed, and a far-field R-wave is absent, loss of capture is confirmed. Additionally, the stimulation device inhibits unnecessary back-up stimulation and threshold tests when fusion occurs, and provides appropriate adjustment of stimulation parameters based on confirmed fusion detection such that fusion re-occurrence is minimized.

Abstract: An implantable cardiac stimulation device and method provide a histogram for storing the number of primary and backup stimulation pulses delivered at each amplitude setting, to monitor the performance of the automatic capture verification. The stimulation device delivers cardiac stimulation therapy in which a stimulation histogram advantageously stores the number of primary pulses delivered at each stimulation output, or range of outputs, and separately stores the number of high-energy backup stimulation pulses delivered. Knowing the historical frequency of the applied stimulation amplitudes is useful to a physician in selecting future stimulation pulse output settings and the working margin. This information is also useful in determining the expected remaining battery life. The stimulation histogram further provides a useful diagnostic tool for evaluating the integrity of the stimulation device, lead system and performance of the automatic capture algorithm.

Abstract: An implantable stimulator device provides automatic electrode polarity switching during an atrial capture verification mode. In systems using a bipolar sensing configuration in the atrium, polarity switching will be advantageous in detecting far-field R-waves for verification of capture. This automatic polarity switching feature is programmable and enables or disables automatic switching from bipolar to unipolar sensing at the onset of a far-field interval window and switching again back to bipolar pacing at the end of the far-field interval window.

Abstract: An implantable cardiac stimulation device applies pacing stimulation pulses to a heart and senses evoked responses to the pacing stimulation pulses. A pulse generator applies the stimulation pacing pulses to the heart in accordance with a pacing configuration. A sensor control selects an evoked response sensing electrode configuration from among a plurality of evoked response sensing electrode configurations in response to the pacing configuration. A sensor is then programmed to sense the evoked responses with the selected evoked response sensing electrode configuration. In accordance with a preferred embodiment, signal-to-noise ratios obtained with the various electrode configurations are used to select a best electrode configuration for sensing evoked responses.

Abstract: An implantable cardiac stimulation device and method automatically verify capture of one or both ventricular chambers by sensing a far-field signal in both atrial chambers. A far-field interval window is set following the delivery of the ventricular stimulation, during which a far-field signal is detected and compared to a signal representing a predetermined far-field R-wave that represents successful capture of one or both ventricular chambers. If the far-field signal is approximately equal to the predetermined far-field R-wave signal, then capture is verified. If capture is not verified, a threshold search is performed in the ventricle in which capture was lost.

Abstract: An implantable cardiac stimulation device and associated method perform an automatic calibration procedure for evaluating whether automatic capture verification can be recommended. The calibration procedure calculates and displays a number of variables for use by a medical practitioner in programming automatic capture operating parameters. An average paced depolarization integral (PDI) is determined from the cardiac signals following delivery of multiple stimulation pulse below and above capture threshold such that both pure lead polarization signals and evoked response signals may be analyzed. From the paced depolarization integral data, a capture threshold, a stimulation response curve, a minimum evoked response, a maximum lead polarization, an evoked response sensitivity, an evoked response safety margin, and a polarization safety margin are determined. Based on these variables, the calibration procedure determines if automatic capture verification can be recommended.

Abstract: An implantable stimulation device delivers a stimulation pulse in a chamber of a patient's heart and perform periodic threshold tests for generating a statistical model of the threshold data, to minimize the number of threshold tests required over a given time. Based on this statistical model, the stimulation pulse energy is automatically adjusted to a level that minimizes the risk of loss of capture. The autocapture safety margin is determined by the variability of the threshold data accumulated over time such that a minimum safety margin can be set to ensure that the delivered pulse energy always exceeds the threshold level. The timing of the trigger events is continuously adjusted to be proportional to the variability of the threshold data. If the standard deviation of the threshold measurements increases, the trigger would occur more often. If the standard deviation decreases, the trigger would be adjusted automatically to occur less often.