Abstract: An implantable medical device system is configured to sense cardiac events in response to a cardiac electrical signal crossing a cardiac event sensing threshold. A control circuit is configured to determine a drop time interval based on a heart rate and control a sensing circuit to hold the cardiac event sensing threshold at a threshold value during the drop time interval.

Abstract: An implantable medical device system capable of sensing cardiac electrical signals includes a sensing circuit, a therapy delivery circuit and a control circuit. The sensing circuit is configured to receive a cardiac electrical signal and sense a cardiac event in response to the signal crossing a cardiac event sensing threshold. The therapy delivery circuit is configured to deliver an electrical stimulation therapy to a patient's heart via the electrodes coupled to the implantable medical device. The control circuit is configured to control the sensing circuit to set a starting value of the cardiac event sensing threshold and hold the starting value constant for a sense delay interval. The control circuit is further configured to detect an arrhythmia based on cardiac events sensed by the sensing circuit and control the therapy delivery circuit to deliver the electrical stimulation therapy in response to detecting the arrhythmia.

Abstract: An implantable medical device system capable of sensing cardiac electrical signals includes a sensing circuit, a therapy delivery circuit and a control circuit. The sensing circuit is configured to receive a cardiac electrical signal and sense a cardiac event in response to the signal crossing a cardiac event sensing threshold. The therapy delivery circuit is configured to deliver an electrical stimulation therapy to a patient's heart via the electrodes coupled to the implantable medical device. The control circuit is configured to control the sensing circuit to set a starting value of the cardiac event sensing threshold and hold the starting value constant for a sense delay interval. The control circuit is further configured to detect an arrhythmia based on cardiac events sensed by the sensing circuit and control the therapy delivery circuit to deliver the electrical stimulation therapy in response to detecting the arrhythmia.

Abstract: An extra-cardiovascular implantable cardioverter defibrillator (ICD) having a high voltage therapy module is configured to control a high voltage charging circuit to charge a capacitor to a pacing voltage amplitude to deliver charge balanced pacing pulses. The capacitor is chargeable to a shock voltage amplitude that is greater than the pacing voltage amplitude. The ICD is configured to enable switching circuitry of the high voltage therapy module to discharge the capacitor to deliver a first pulse having a first polarity and a leading voltage amplitude corresponding to the pacing voltage amplitude for pacing the patient's heart via a pacing electrode vector selected from extra-cardiovascular electrodes. The high voltage therapy module delivers a second pulse after the first pulse. The second pulse has a second polarity opposite the first polarity and balances the electrical charge delivered during the first pulse.

Abstract: An implantable cardioverter defibrillator (ICD) starts a timer set to a time interval in response to a cardiac electrical signal crossing a noise threshold amplitude and resets the timer to the time interval in response to each crossing of the noise threshold amplitude by the cardiac electrical signal that occurs prior to the time interval expiring. A control circuit of the ICD determines a parameter of the behavior of the timer and identifies a sensed cardiac event as an electromagnetic interference (EMI) event based on the parameter. The ICD may detect EMI in response to the EMI event and withhold a tachyarrhythmia detection or therapy in response to EMI detection.

Abstract: An implantable medical device system capable of sensing cardiac electrical signals includes a sensing circuit, a therapy delivery circuit and a control circuit. The sensing circuit is configured to receive a cardiac electrical signal and sense a cardiac event in response to the signal crossing a cardiac event sensing threshold. The therapy delivery circuit is configured to deliver an electrical stimulation therapy to a patient's heart via the electrodes coupled to the implantable medical device. The control circuit is configured to control the sensing circuit to set a starting value of the cardiac event sensing threshold and hold the starting value constant for a sense delay interval. The control circuit is further configured to detect an arrhythmia based on cardiac events sensed by the sensing circuit and control the therapy delivery circuit to deliver the electrical stimulation therapy in response to detecting the arrhythmia.

Abstract: An implantable pacemaker detects delivery of an anti-tachyarrhythmia shock by another device. The implantable pacemaker delivers cardiac stimulation therapy within a patient. The implantable pacemaker senses, via the electrode pair, an electrical signal. The implantable pacemaker detects the anti-tachyarrhythmia shock based on the sensed electrical signal by detecting DC voltage polarization across the electrode pair within the patient. The implantable pacemaker alters the cardiac stimulation therapy based on the detected anti-tachyarrhythmia shock.

Abstract: An implantable device and associated method for delivering multi-site pacing therapy is disclosed. The device comprises a set of electrodes including a first ventricular electrode and a second ventricular electrode, spatially separated from one another and all coupled to an implantable pulse generator. The device comprises a processor configured for selecting a first cathode and a first anode from the set of electrodes to form a first pacing vector at a first pacing site along a heart chamber and selecting a second cathode and a second anode from the set of electrodes to form a second pacing vector at a second pacing site along the same heart chamber. The pulse generator is configured to deliver first pacing pulses to the first pacing vector and delivering second pacing pulses to the second pacing vector. The pulse generator generates a recharging current for recharging a first coupling capacitor over a first recharge time period in response to the first pacing pulses.

Abstract: An implantable pacemaker detects delivery of an anti-tachyarrhythmia shock by another device. The implantable pacemaker delivers cardiac stimulation therapy within a patient. The implantable pacemaker senses, via the electrode pair, an electrical signal. The implantable pacemaker detects the anti-tachyarrhythmia shock based on the sensed electrical signal by detecting DC voltage polarization across the electrode pair within the patient. The implantable pacemaker alters the cardiac stimulation therapy based on the detected anti-tachyarrhythmia shock.

Abstract: An implantable pacemaker detects delivery of an anti-tachyarrhythmia shock by another device. The implantable pacemaker delivers cardiac stimulation therapy within a patient. The implantable pacemaker senses, via the electrode pair, an electrical signal. The implantable pacemaker detects the anti-tachyarrhythmia shock based on the sensed electrical signal by detecting DC voltage polarization across the electrode pair within the patient. The implantable pacemaker alters the cardiac stimulation therapy based on the detected anti-tachyarrhythmia shock.

Abstract: This disclosure describes a chopper-stabilized sigma-delta analog-to-digital converter (ADC). The ADC is configured to provide accurate output at low frequency with relatively low power. The chopper-stabilized ADC substantially reduces or eliminates noise and offset from an output signal produced by the mixer amplifier. Dynamic limitations, i.e., glitching that result from chopper stabilization at low power are substantially eliminated or reduced through a combination of chopping at low impedance nodes within the mixer amplifier and feedback. The signal path of the ADC operates as a continuous time system, providing minimal aliasing of noise or external signals entering the signal pathway at the chop frequency or its harmonics. In this manner, the chopper-stabilized ADC can be used in a low power system, such as an implantable medical device (IMD), to provide a stable, low-noise output signal.

Abstract: In general, this disclosure describes techniques for reducing power consumption within an implantable medical device (IMD). An IMD implanted within a patient may have finite power resources that are intended to last several years. To promote device longevity, sensing and therapy circuits of the IMD are designed to incorporate an analog-to-digital converter (ADC) that provides relatively high resolution output at a relatively low operation frequency, and does so with relatively low power consumption. An ADC designed in accordance with the techniques described herein utilizes a quantizer that has a lower resolution than a digital-to-analog converter (DAC) used for negative feedback. Such a configuration provides the benefits of higher resolution DAC feedback without having the use high oversampling ratios that result in high power consumption. Also, the techniques avoid the use of, and the associated high power consumption of, a high resolution flash ADC, within the sigma delta loop.

Abstract: This disclosure describes a chopper-stabilized sigma-delta analog-to-digital converter (ADC). The ADC is configured to provide accurate output at low frequency with relatively low power. The chopper-stabilized ADC substantially reduces or eliminates noise and offset from an output signal produced by the mixer amplifier. Dynamic limitations, i.e., glitching that result from chopper stabilization at low power are substantially eliminated or reduced through a combination of chopping at low impedance nodes within the mixer amplifier and feedback. The signal path of the ADC operates as a continuous time system, providing minimal aliasing of noise or external signals entering the signal pathway at the chop frequency or its harmonics. In this manner, the chopper-stabilized ADC can be used in a low power system, such as an implantable medical device (IMD), to provide a stable, low-noise output signal.

Abstract: In general, this disclosure describes techniques for reducing power consumption within an implantable medical device (IMD). An IMD implanted within a patient may have finite power resources that are intended to last several years. To promote device longevity, sensing and therapy circuits of the IMD are designed to incorporate an analog-to-digital converter (ADC) that provides relatively high resolution output at a relatively low operation frequency, and does so with relatively low power consumption. An ADC designed in accordance with the techniques described herein utilizes a quantizer that has a lower resolution than a digital-to-analog converter (DAC) used for negative feedback. Such a configuration provides the benefits of higher resolution DAC feedback without having the use high oversampling ratios that result in high power consumption. Also, the techniques avoid the use of, and the associated high power consumption of, a high resolution flash ADC, within the sigma delta loop.

Abstract: In general, this disclosure describes techniques for capacitive digit-to-analog converter (CAPDAC) resetting in an implantable medical device (IMD) analog-to-digital converter (ADC). The CAPDAC of an IMD ADC may occasionally be reset to increase the accuracy of its output. The output of the CAPDAC may be disconnected from a negative feedback input of an integrator and connected to a pseudo load during the reset. Disconnecting the CAPDAC from the negative feedback input of the integrator reduces the affect of the reset on the integrator. During the reset of the CAPDAC, the negative feedback input of integrator is coupled to a sample and hold capacitor, which temporarily provides an input approximately equal to a previous, e.g., immediate, value of the output of CAPDAC prior to the reset. Thus, the resetting of the CAPDAC is done in such a manner that the affect of the reset on integrator is substantially reduced or eliminated.

Abstract: In general, this disclosure is related to detecting overload within an analog-to-digital converter (ADC) of an implantable medical device (IMD). The IMD may include an overload detection module that determines whether the ADC is operating in an overload condition. When the overload detection module determines the ADC is operating in the overload condition for a particular period of time, the ADC may send an overload signal to a processor that processes the output of the ADC. The overload signal notifies the processor that the ADC is operating in or is close to operating in the overload condition. In response to the indication from the ADC, the processor of the IMD may disregard the output of the ADC. The processor may continue to disregard the output of the ADC until the overload signal is deactivated, thereby indicating that the ADC is no longer in an overloaded condition.

Abstract: An implantable medical device, such as a pacemaker or implantable cardioverter defibrillator, uses digital signal processing channels to process sensed time varying signals representing cardiac activity. Each digital signal processing channels includes a sigma-Delta analog-to-digital converter. The clock rate of each sigma-delta analog-to-digital converter is controlled as a function of a signal detection threshold for its respective digital signal processing channel. For higher threshold levels, a reduced clock rate for the sigma-delta analog-to-digital converter results in reduced power consumption and longer battery life.

Abstract: An implantable medical device, such as a pacemaker or implantable cardioverter defibrillator, uses digital signal processing channels to process sensed time varying signals representing cardiac activity. Each digital signal processing channels includes a sigma-Delta analog-to-digital converter. The clock rate of each sigma-delta analog-to-digital converter is controlled as a function of a signal detection threshold for its respective digital signal processing channel. For higher threshold levels, a reduced clock rate for the sigma-delta analog-to-digital converter results in reduced power consumption and longer battery life.

Abstract: A cardiac pacing device and method for automatically selecting an optimal evoked response sensing vector based on an evaluation of the evoked response signal quality are provided. Electrode switching circuitry allows selection of multiple sensing electrode vectors. Capture detection circuitry provides capture and loss of capture signal characteristics determined during a pacing threshold search to be used in determining evoked response signal quality parameters. An optimal evoked response sensing vector is selected based on evoked response signal quality parameters meeting predetermined criteria for reliable evoked response sensing.

Abstract: A system and method for acquiring and processing an EGM signal during a pacing event, wherein a unique converter code is generated upon digitizing of the EGM signal and encrypted in the EGM signal to demarcate a transient event. The system further provides dynamic filtering of the EGM signal and subsequent detection of an intrinsic event signal during the pacing event, from which rhythm events may be diagnosed and classified.