Abstract: A medical device is configured to determine tachyarrhythmia evidence in a cardiac signal segment received from a cardiac electrical signal sensed during a pacing escape interval started to schedule a pending cardiac pacing pulse. The medical device may delay the pending cardiac pacing pulse in response to determining the tachyarrhythmia evidence during the pacing escape interval.

Abstract: A medical device is configured to sense first ventricular event signals from a first cardiac electrical signal and sense second ventricular event signals from a second cardiac electrical signal. The medical device is configured to determine sensed event data in response to the first ventricular event signals and the second ventricular event signals. The medical device may select one of the first cardiac electrical signal or the second cardiac electrical signal for providing input for tachyarrhythmia detection based on the sensed event data.

Abstract: A medical device is configured to receive cardiac electrical signals and sense ventricular event signals from the cardiac electrical signals. The medical device may start a validation window in response to sensing a ventricular event signal and determine if the ventricular event signal is a valid event signal or an invalid event signal based on processing of a different cardiac electrical signal than the cardiac electrical signal from which the ventricular event signal was sensed.

Abstract: A medical device is configured to determine tachyarrhythmia evidence in a cardiac signal segment received from a cardiac electrical signal sensed during a pacing escape interval started to schedule a pending cardiac pacing pulse. The medical device may delay the pending cardiac pacing pulse in response to determining the tachyarrhythmia evidence during the pacing escape interval.

Abstract: A medical device is configured to sense first ventricular event signals from a first cardiac electrical signal and sense second ventricular event signals from a second cardiac electrical signal. The medical device is configured to determine sensed event data in response to the first ventricular event signals and the second ventricular event signals. The medical device may select one of the first cardiac electrical signal or the second cardiac electrical signal for providing input for tachyarrhythmia detection based on the sensed event data.

Abstract: A medical device is configured to set a post-atrial time interval in response to an atrial event and generate an event time signal in response to a ventricular electrical signal crossing an R-wave sensing threshold during the post-atrial time interval. The device accumulates oversensing evidence in response to the event time signal and adjusts a ventricular sensing control parameter based on the accumulated oversensing evidence in some examples.

Abstract: A medical device is configured to receive cardiac electrical signals and sense ventricular event signals from the cardiac electrical signals. The medical device may start a validation window in response to sensing a ventricular event signal and determine if the ventricular event signal is a valid event signal or an invalid event signal based on processing of a different cardiac electrical signal than the cardiac electrical signal from which the ventricular event signal was sensed.

Abstract: An example device includes a memory configured to store representations of sensed signals. The example device includes processing circuitry coupled to the memory, the processing circuitry being configured to read or write the representations of the sensed signals in the memory. The example device includes sensing circuitry coupled to the processing circuitry, the sensing circuitry being configured to sense signals indicative of a physiological condition of a patient via a plurality of electrodes and to output to the processor circuitry the representations of the sensed signals. The sensing circuitry includes a switched capacitor charge pump configured to amplify the sensed signals to generate amplified signals.

Abstract: Implantable medical devices include a first sensor for detecting a magnetic field that indicates an exposure mode of operation is appropriate. The implantable medical devices include a second sensor for detecting whether an MRI characteristic is present that indicates whether MRI or non-MRI post exposure diagnostics and other actions should be implemented and may also indicate whether the exposure mode should be MRI or non-MRI specific. An MRI post exposure diagnostic may perform pacing capture threshold tests and the post exposure pacing amplitude output may be kept at a higher than normal level. The second sensor may be an overvoltage clamp circuit of a telemetry coil that indicates whether an overvoltage condition on the telemetry coil is occurring to indicate whether an MRI characteristic is present. The second sensor may be a second threshold magnetic sensor, an accelerometer, or a microphone to indicate whether an MRI characteristic is present.

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: A medical device comprises a sensing circuit configured to sense at least one cardiac electrical signal, sense first ventricular event signals from the at least one cardiac electrical signal according to a sensitivity setting set to a first amplitude; and a control circuit in communication with the sensing circuit, the control circuit configured to determine that the at least one cardiac electrical signal meets suspected undersensing criteria, in response to determining that the suspected undersensing criteria are met, perform a morphology analysis of a first cardiac signal segment acquired from a first cardiac electrical signal of the at least one cardiac electrical signal sensed by the sensing circuit over a first predetermined time interval, determine that the first cardiac signal segment is a first tachyarrhythmia segment based on the morphology analysis, and adjust the sensitivity setting from the first amplitude to a second amplitude less than the first amplitude in response to determining that the firs

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 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 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: A medical device is configured to set a post-atrial time interval in response to an atrial event and generate an event time signal in response to a ventricular electrical signal crossing an R-wave sensing threshold during the post-atrial time interval. The device accumulates oversensing evidence in response to the event time signal and adjusts a ventricular sensing control parameter based on the accumulated oversensing evidence in some examples.

Abstract: A medical device is configured to set a post-atrial time interval in response to an atrial event and generate an event time signal in response to a ventricular electrical signal crossing an R-wave sensing threshold during the post-atrial time interval. The device accumulates oversensing evidence in response to the event time signal and adjusts a ventricular sensing control parameter based on the accumulated oversensing evidence in some examples.

Abstract: Implantable medical devices include a first sensor for detecting a magnetic field that indicates an exposure mode of operation is appropriate. The implantable medical devices include a second sensor for detecting whether an MRI characteristic is present that indicates whether MRI or non-MRI post exposure diagnostics and other actions should be implemented and may also indicate whether the exposure mode should be MRI or non-MRI specific. An MRI post exposure diagnostic may perform pacing capture threshold tests and the post exposure pacing amplitude output may be kept at a higher than normal level. The second sensor may be an overvoltage clamp circuit of a telemetry coil that indicates whether an overvoltage condition on the telemetry coil is occurring to indicate whether an MRI characteristic is present. The second sensor may be a second threshold magnetic sensor, an accelerometer, or a microphone to indicate whether an MRI characteristic is present.

Abstract: A medical device is configured to determine tachyarrhythmia evidence in a cardiac signal segment received from a cardiac electrical signal sensed during a pacing escape interval started to schedule a pending cardiac pacing pulse. The medical device may delay the pending cardiac pacing pulse in response to determining the tachyarrhythmia evidence during the pacing escape interval.

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: A medical device is configured to receive cardiac electrical signals and sense ventricular event signals from the cardiac electrical signals. The medical device may start a validation window in response to sensing a ventricular event signal and determine if the ventricular event signal is a valid event signal or an invalid event signal based on processing of a different cardiac electrical signal than the cardiac electrical signal from which the ventricular event signal was sensed.