Abstract: A filtering scheme for an implantable medical device mitigates potentially adverse effects that may be caused by MRI-induced signals. In some aspects filtering is provided to attenuate MRI-induced signals on an implanted cardiac lead that is coupled to an implanted device. In some aspects the filter may be configured to complement a capacitor circuit (e.g., a feedthrough capacitor) that reduces the amount of EMI that enters the implanted device via the cardiac lead. In some implementations the filter consists of a LC tank circuit and a series LC circuit, where the LC tank circuit is in series with the cardiac lead and a cardiac stimulation circuit and the series LC circuit is in a shunt configuration across the cardiac stimulation circuit.

Abstract: A surface electrocardiogram (EKG) is emulated using signals detected by the internal leads of an implanted device. In one example, the emulation is performed using a technique that concatenates portions of signals sensed using different electrodes. In another example, the emulation is performed using a technique that selectively amplifies or attenuates portions of a single cardiac signal sensed using a single pair of electrodes. The surface EKG emulation may be performed by the implanted device itself or by an external device, such as a programmer, based on cardiac signals transmitted thereto. The external device then displays the emulated surface EKG along with an intracardiac electrogram (IEGM) and set of event markers. Alternatively, the external device displays an entire set of emulated EKGs that had been generated based on the same patient input data but using different emulation techniques.

Abstract: An exemplary method includes detecting a first atrial event, initiating a detection window after detecting the first atrial event, detecting a second atrial event during the detection window, classifying the second atrial event as a premature atrial contraction and calling for delivery of an atrial extrastimulus in response to the premature atrial contraction. Various other exemplary technologies are also disclosed.

Abstract: An implanted cardiac rhythm management device is disclosed that is operative to detect myocardial ischemia. This is done by evaluating electrogram features to detect an electrocardiographic change; specifically, changes in electrogram segment during the early part of an ST segment. The early part of the ST segment is chosen to avoid the T-wave.

Abstract: An exemplary method includes detecting arrhythmia, detecting myocardial ischemia, determining whether the myocardial ischemia comprises local ischemia or global ischemia and, in response to the determining, calling for delivery of either a local ischemic anti-arrhythmia therapy or a global ischemic anti-arrhythmia therapy. Various other exemplary methods, devices, systems, etc., are also disclosed.

Abstract: An implantable cardiac device is programmed to detect and classify premature atrial contractions (PACs) and administer responsive pacing therapy. The responsive pacing therapy is in the form of an atrial extrastimulus, which is intended to preempt initiation of a reentrant tachycardia. The atrial extrastimulus is timed to occur late enough after a PAC to ensure atrial capture, but early enough that the resulting atrial depolarization does not conduct through the AV node to the ventricles if the PAC has already done so. If both of these criteria cannot be met, the device may be configured to inhibit the atrial extrastimulus.

Abstract: An implantable cardiac device is programmed to detect and classify premature atrial contractions (PACs). In the described implementation, the device uses timing based techniques to distinguish PACs from native sinus P-waves. The device is also able to detect and count a salvo of consecutive PACs for diagnostic purposes.

Abstract: A Fast Fourier Transform (FFT) converts time-varying event waveforms into the frequency domain waveforms to thereby decompose the events into their spectral components, which are analyzed to distinguish R-waves from T-waves. In some embodiments, the FFT is only activated if a ventricular tachyarrhythmia is already indicated. For example, an initial ventricular rate may be derived from a ventricular IEGM based on all events detected therein. The initial ventricular rate is compared against one or more thresholds representative of ventricular tachycardia (VT) and/or ventricular fibrillation (VF) to determine if VT/VF is indicated. If so, the FFT is activated to distinguish R-waves from T-waves and, in particular, to detect and eliminate T-wave oversensing. Then, the ventricular rate is re-determined based only on the rate of true R-waves. Therapy is delivered if VT/VF is still detected.

Abstract: A method and apparatus for treating an arrhythmia is provided. The method includes the steps of: (a) sensing at least one electrical signal from the patient's heart; (b) calculating a frequency spectrum of each electrical signal; (c) calculating a center frequency for each frequency spectrum; and (d) selecting an electro-therapy for delivery to the patient's heart based on the center frequency. The electro-therapy can be a pre-programmed anti-tachycardia pacing (ATP) therapy, a shock therapy, or no therapy at all. The method is performed through the use of an implantable cardioverter defibrillator (ICD). Also provided is a method of determining the optimal location to deliver the electro-therapy.

Abstract: Techniques are provided for controlling ventricular pacing during an episode of atrial fibrillation (AF) for use by a pacemaker, implantable cardioverter-defibrillator (ICD) or other implantable medical device. In one example, upon detection of AF, the underlying intrinsic ventricular rate of the patient is determined prior to delivering any ventricular pacing. Then, a ventricular pacing procedure—such as dynamic ventricular overdrive (DVO) pacing—is activated to reduce ventricular rate variability to mitigate the adverse effects of AF. The ventricular pacing procedure employed during AF is controlled based on a maximum ventricular rate set relative to the underlying intrinsic ventricular rate so as to keep an overall ventricular rate below the maximum rate.

Abstract: An implantable cardiac device is programmed to detect and classify premature atrial contractions (PACs) and administer responsive pacing therapy. The responsive pacing therapy is in the form of an atrial extrastimulus, which is intended to preempt initiation of a reentrant tachycardia. The atrial extrastimulus is timed to occur late enough after a PAC to ensure atrial capture, but early enough that the resulting atrial depolarization does not conduct through the AV node to the ventricles if the PAC has already done so. If both of these criteria cannot be met, the device may be configured to inhibit the atrial extrastimulus.

Abstract: An implanted cardiac rhythm management device is disclosed that is operative to detect myocardial ischemia. This is done by evaluating electrogram features to detect an electrocardiographic change; specifically, changes in electrogram segment during the early part of an ST segment. The early part of the ST segment is chosen to avoid the T-wave.

Abstract: Techniques are described for adaptively adjusting detection thresholds for use in detecting cardiac ischemia and other abnormal physiological conditions based on morphological parameters derived from intracardiac electrogram (IEGM) signals, impedance measurements, or other signals. In one example, where ST segment elevation is used to detect cardiac ischemia, default detection thresholds are determined in advance from an examination of variations in ST segment elevations occurring within a population of patients. Thereafter, an individual pacemaker or other implantable medical device uses the default thresholds during an initial learning period to detect ischemia within the patient in which the device is implanted. During the initial learning period, the pacemaker also collects data representative of the range of variation in ST segment elevations occurring within the patient.

Abstract: Techniques are described for efficiently detecting and distinguishing among cardiac ischemia, hypoglycemia or hyperglycemia based on intracardiac electrogram (IEGM) signals. In one example, a preliminary indication of an episode of cardiac ischemia is detected based on shifts in ST segment elevation within the IEGM. In response, the implanted device then records additional IEGM data for transmission to an external system. The external system analyzes the additional IEGM data to confirm the detection of cardiac ischemia using a more sophisticated analysis procedure exploiting additional detection parameters. In particular, the external system uses detection parameters capable of distinguishing hypoglycemia, hyperglycemia and hyperkalemia from cardiac ischemia, such as QTmax and QTend intervals. Alternatively, the more sophisticated analysis procedure may be performed by the device itself, if it is so equipped. Other examples described herein pertain instead to the detection of atrial fibrillation.

Abstract: A process for determining whether the location of a stimulation electrode meets a selected heart performance criteria includes providing stimulation to the heart through the electrode and obtaining an impedance measurement during stimulation delivery using an impedance sensing vector formed by electrodes that do not include the stimulation electrode. The impedance measurements are processed, either alone or in combination with an electrogram, also obtained during stimulation, to obtain a measure of hemodynamic performance.

Abstract: Methods and systems are presented for using an ICD to detect myocardial ischemia. One such method includes sensing via an implantable cardiac-rhythm-management device (ICRMD) a signal indicative of cardiac pressure; determining via a processor associated with the ICRMD, a derivative signal that is a first derivative of the sensed signal; measuring via the processor, a maximum positive value of the derivative signal; measuring via the processor, a maximum negative value of the derivative signal; and indicating via the processor, an ischemia based on a comparison of a ratio of the maximum positive value to the maximum negative value with a predetermined value.

Abstract: Methods and systems are presented for using an ICD to detect myocardial ischemia. In one embodiment, a method includes sensing a signal indicative of cardiac pressure, measuring a height of the sensed signal at a peak amplitude of the sensed signal, and measuring a duration of the sensed signal. The method further includes indicating an ischemia based on a comparison of a ratio of the height to the duration with a predetermined value. In another embodiment, a method includes sensing a signal indicative of cardiac pressure, determining a derivative signal that is a first derivative of the sensed signal, measuring a maximum positive value of the derivative signal, and measuring a maximum negative value of the derivative signal. The method further includes indicating an ischemia based on a comparison of a ratio of the maximum positive value to the maximum negative value with a predetermined value.

Abstract: An exemplary method includes detecting arrhythmia, detecting myocardial ischemia, determining whether the myocardial ischemia comprises local ischemia or global ischemia and, in response to the determining, calling for delivery of either a local ischemic anti-arrhythmia therapy or a global ischemic anti-arrhythmia therapy. Various other exemplary methods, devices, systems, etc., are also disclosed.

Abstract: The implantable device is capable of performing thermal dilution analysis of the cardiac output of a patient using power delivered from an external source. By using power from an external source, the implantable device conserves its power resources for other purposes, such as for pacing or defibrillation therapy. In one example, an external programmer or bedside monitor provides power through a hand-held power delivery wand via electromagnetic induction, with the power routed from a subcutaneous coil to a heating element implanted in the right atrium, which heats blood as it passes through the right atrium. In another example, the heating element is formed of a material that generates heat in response to a beam of ultrasound provided by the wand. In either case, a downstream blood temperature profile is detected using a thermistor implanted in the pulmonary artery and cardiac output is then estimated by analyzing the temperature profile.

Abstract: An implantable cardiac system including an implantable cardiac stimulation device provides a heart activity signal of a heart facilitating measurement of slowly changing electrogram features. The system comprises at least one implantable electrode arrangement that senses cardiac electrical activity and provides an intracardiac electrogram signal, a first high pass filter that filters the electrogram and an equalizer that filters the filtered electrogram signal. The equalizer has a transfer function that is non-decreasing for frequencies up to a lower frequency breakpoint that is less than the upper frequency breakpoint, decreasing for frequencies between the lower frequency breakpoint and the upper frequency breakpoint, and generally flat for frequencies above the upper frequency breakpoint through a bandpass region of interest.