Abstract: A cardiac medical device and associated method control delivery of anti-tachycardia pacing (ATP) in response to detecting tachycardia. In one embodiment, an initial set of single chamber pacing pulses are delivered in a single one of the atrium and the ventricle, the other one of the atrium and the ventricle being a non-paced chamber during the initial set of single chamber pacing pulses. The device detects simultaneity between a sensed event in the non-paced chamber and one of the single chamber pacing pulses and delivers ATP in both the atrium and the ventricle in response to detecting the simultaneity.

Abstract: Methods and apparatus are provided for discriminating high rate polymorphic QRS complexes from high rate monomorphic QRS complexes to increase the specificity of detection of polymorphic VT and VF employing wavelet transform signal processing of the QRS complexes are disclosed. Wavelet transforms are applied to the sampled amplitude values of a sequence of QRS complexes to develop wavelet transform coefficient (WTC) data sets. At least selected ones of the WTC data sets are processed and comparisons are made to determine a wavelet match score. A determination is made as a function of the wavelet match scores of the series of successive QRS complexes that characterizes the most recent QRS complex as more or less likely to signify polymorphic VT or VF.

Abstract: A medical device and associated method for monitoring a patient's heart rhythm sense cardiac events and detect a sudden change in the heart rhythm in response to the sensed cardiac events. Detecting the sudden change includes determining a variability of intervals between the sensed cardiac events and switching between a low variability mode of operation and a high variability mode of operation in response to the variability of intervals. During the low variability mode, detecting the sudden change includes detecting an increase in the rate of cardiac events. During the high variability mode, detecting the sudden change includes detecting a sudden decrease in the variability of the cardiac event intervals. A concerning cardiac rhythm is detected in response to detecting the sudden change.

Abstract: A method and apparatus for monitoring a patient's heart rate sense first cardiac events in a heart chamber using a first cardiac electrode pair and sense second cardiac events in the heart chamber using a second cardiac electrode pair. The method includes estimating a first heart rate using the first cardiac events, comparing the first heart rate to a heart rate threshold and estimating a second heart rate using the second cardiac events in response to the first heart rate exceeding the heart rate threshold.

Abstract: A method of detecting a cardiac event that includes sensing cardiac signals from a plurality of electrodes, determining rates of change of the sensed cardiac signals, and determining a range of the sensed cardiac signals. The sensed cardiac signals are detected as being associated with the cardiac event in response to the determined rates of change and the determined range.

Abstract: A cardiac medical device and associated method control delivery of dual chamber burst pacing pulses in response to detecting tachycardia. In one embodiment, a single chamber pacing pulse is delivered in response to detecting a tachycardia. Dual chamber pacing pulses are delivered subsequent to the single chamber pacing pulse. An intrinsic depolarization is sensed subsequent to delivering the dual chamber pacing pulses. The tachycardia episode is classified in response to the sensed intrinsic depolarization.

Abstract: A first implantable medical device (IMD) implanted within a patient may communicate with a second IMD implanted within the patient by encoding information in an electrical stimulation signal. The delivery of the electrical stimulation signal may provide therapeutic benefits to the patient. The second IMD may sense the electrical stimulation signal, which may be presented as an artifact in a sensed cardiac signal, and process the sensed signal to retrieve the encoded information. The second IMD may modify its operation based on the received therapy information. Crosstalk between the first and second IMDs may be reduced using various techniques described herein. For example, the first IMD may generate the electrical stimulation signal to include a spread spectrum energy distribution or a predetermined signal signature. The second IMD may effectively remove a least some of the signal artifact in a sensed cardiac signal based on the predetermined signal signature.

Abstract: A medical device and associated method for discriminating cardiac events sense cardiac signals that includes determining whether a first match score is within one of a first match zone corresponding to a first cardiac event, and a second match zone corresponding to the first cardiac event, and determining whether a second match score is within one of the first match zone, the second match zone, and a third match zone corresponding to a second cardiac event different from the first cardiac event. One of increasing and decreasing an event counter is performed in response to both the determination of whether the first match score is within one of the first match zone and the second match zone and the determination of whether the second match score is within one of the first match zone, the second match zone, and the third match zone.

Abstract: With a method and apparatus for detecting cardiac arrhythmias during overdrive pacing, a maximum paced rate and a reduced paced rate for a heart are determined, the maximum paced rate being higher than the reduced paced rate. The heart is paced at the maximum paced rate. After the heart is paced at the maximum paced rate for a predetermined amount of time, the heart is paced at the reduced paced rate.

Abstract: An implantable medical device having an optical sensor selects the function of modular opto-electronic assemblies included in the optical sensor. Each assembly is provided with at least one light emitting device and at least one light detecting device. A device controller coupled to the optical sensor controls the function of each the assemblies. The controller executes a sensor performance test and selects at least one of the plurality of assemblies to operate as a light emitting assembly in response to a result of the performance test. The controller selects at least one other of the plurality of optical sensor assemblies to operate as a light detecting assembly in response to a result of the performance test.

Abstract: A method comprises monitoring a heart rate, a respiration rate and an activity level of a patient, comparing the monitored heart rate, respiration rate and activity level to a predetermined threshold zone which is a function of heart rate, respiration rate and activity level, determining the patient is experiencing worsening heart failure when the monitored heart rate, respiration rate and activity level are outside the predetermined threshold zone; and after determining the patient is experiencing worsening heart failure when the monitored heart rate, respiration rate and activity level are outside the predetermined threshold zone, issuing an alert to indicate that the patient is experiencing worsening heart failure.

Abstract: A medical device and associated method for discriminating cardiac events includes determining whether a first match score is within a first match zone having a first correlation with a non-treatable cardiac event, a second match zone having a second correlation with the non-treatable cardiac event less than the first correlation, a third match zone having a first correlation with a treatable cardiac event, and a fourth match zone having a second correlation with the treatable cardiac event greater than the first correlation with the treatable cardiac event. In response to the first match score being within one of the first and second match zones, a determination is made whether consecutive match scores are within the first match zone and whether a break in the treatable cardiac event has occurred. Cardiac evidence is accumulated in response to determining whether a break has occurred and utilized to discriminate cardiac events.

Abstract: An implantable pacing system with single, double and triple chamber pacing capabilities, provided individually or in concert on a conditional or continuous basis depending upon ongoing analyses of atrial rhythm status, atrioventricular conduction status and ventricular rate. A mode is selected to reduce the occurrence of any ventricular pacing in favor of intrinsic atrioventricular and ventricular conduction. If excessively long PR intervals are occurring too frequently or atrioventricular conduction is unreliable or absent, the implantable pulse generator is operated in a conditional triple chamber pacing mode that provides atrial-synchronous biventricular pacing in every cardiac cycle for a period of time as necessary to restore and maintain AV synchrony, while minimizing ventricular asynchrony otherwise associated with monochamber RV pacing as in conventional dual chamber pacing systems.

Abstract: An implantable medical device for monitoring tissue perfusion that includes a light source emitting a light signal and a light detector receiving emitted light scattered by a volume of body tissue. The light detector emits a signal having an alternating current component corresponding to the pulsatility of blood flow in the body tissue volume. A processor receives the current signal and determines a patient condition in response to the alternating component of the current signal.

Abstract: Techniques for processing impedance data to provide an early warning for heart failure decompensation are described. An example device may be configured to measure intrathoracic impedance values, and increment an index when a determined impedance is less than a reference impedance. The incrementing may be based on the difference between the reference impedances and the determined impedance. In some examples, the amount of incrementing is reduced based on a variability of the impedances, or increased over time so long as the index remains above a threshold, e.g., zero. In some examples, the manner is which the reference impedances are determined changes over time to, for example, address rapid changes in impedance after device or system implantation. In some examples, the index is compared to a threshold to determine whether to provide an alert. In some examples, two thresholds are used to provide hysteresis.

Abstract: This disclosure relates to monitoring intracardiac or vascular impedance to determine a change in hemodynamic status by detecting changes in an impedance parameter over cardiac cycles. An example method includes measuring a plurality of impedance values of a path within a patient over time, wherein the path includes at least one blood vessel or cardiac chamber of the patient, and wherein the impedance values vary as a function of blood pressure within the at least one vessel or chamber, determining a plurality of values of an impedance parameter over time based on the measured impedance values, wherein each of the impedance parameter values is determined based on a respective sub-plurality of the impedance values, comparing at least one of the impedance parameter values to at least one prior impedance parameter value, and identifying a change in a cardiovascular parameter related to the blood pressure based on the comparison.

Abstract: An implantable medical device system and associated method monitor changes in transimpedance in a body tissue due to changes in cardiac pulsatility. A first dipole is used to deliver a non-stimulating electrical current. The first dipole includes a first electrode and a second electrode adapted to be deployed along a first body location. A second dipole is used to measure a voltage resulting from the non-stimulating electrical current being conducted through a portion of a patient's body. The second dipole includes a third electrode and a fourth electrode different than the first electrode and the second electrode and adapted to be deployed along a second body location spaced apart from the first body location.

Abstract: An implantable pacing system with single, double and triple chamber pacing capabilities, provided individually or in concert on a conditional or continuous basis depending upon ongoing analyses of atrial rhythm status, atrioventricular conduction status and ventricular rate. A mode is selected to reduce the occurrence of any ventricular pacing in favor of intrinsic atrioventricular and ventricular conduction. If excessively long PR intervals are occurring too frequently or atrioventricular conduction is unreliable or absent, the implantable pulse generator is operated in a conditional triple chamber pacing mode that provides atrial-synchronous biventricular pacing in every cardiac cycle for a period of time as necessary to restore and maintain AV synchrony, while minimizing ventricular asynchrony otherwise associated with monochamber RV pacing as in conventional dual chamber pacing systems.

Abstract: A medical device for determining a respiratory effort having a pressure sensor to sense pressure signals, a housing having system components positioned therein, and a microprocessor positioned within the housing, wherein the microprocessor detects an inspiration and an expiration in response to the pressure signals, detects a breath in response to the detected inspiration and the detected expiration, and determines the respiratory effort in response to the detected breath.

Abstract: An implantable pacing system with single, double and triple chamber pacing capabilities, provided individually or in concert on a conditional or continuous basis depending upon ongoing analyses of atrial rhythm status, atrioventricular conduction status and ventricular rate. A mode is selected to reduce the occurrence of any ventricular pacing in favor of intrinsic atrioventricular and ventricular conduction. If excessively long PR intervals are occurring too frequently or atrioventricular conduction is unreliable or absent, the implantable pulse generator is operated in a conditional triple chamber pacing mode that provides atrial-synchronous biventricular pacing in every cardiac cycle for a period of time as necessary to restore and maintain AV synchrony, while minimizing ventricular asynchrony otherwise associated with monochamber RV pacing as in conventional dual chamber pacing systems.