A device includes a sensor signal input node and a high-pass filter stage. The high-pass filter stage includes an operational amplifier and a feedback integrator. The operational amplifier includes an input node coupled to the sensor signal input node. The feedback integrator is coupled between an output node of the operational amplifier and the input node of the operational amplifier to set a high-pass pole frequency of the high-pass filter stage.

Some method examples may include pacing a heart with cardiac paces, sensing a physiological signal for use in detecting pace-induced phrenic nerve stimulation, performing a baseline level determination process to identify a baseline level for the sensed physiological signal, and detecting pace-induced phrenic nerve stimulation using the sensed physiological signal and the calculated baseline level. Detecting pace-induced phrenic nerve stimulation may include sampling the sensed physiological signal during each of a plurality of cardiac cycles to provide sampled signals and calculating the baseline level for the physiological signal using the sampled signals. Sampling the sensed physiological signal may include sampling the signal during a time window defined using a pace time with each of the cardiac cycles to avoid cardiac components and phrenic nerve stimulation components in the sampled signal.

Systems and methods for determining brain health of a subject include or employ an electrical stimulator configured to apply a current to at least one pair of electrodes, and the electrodes are positioned on a skull of the subject to apply the current and to receive brain activity of the subject. The electrical stimulator is configured to apply a current having a waveform according to a Stochastic Gabor Function (SGF). A signal processor is configured to record the brain activity of the subject in the form of spectral electrical impedance data, and a computer system having non-transient computer readable media is programmed and configured to process the spectral electrical impedance data and indicate an impedance change within the brain of the subject.

An implantable device for controlling electrical conditions of body tissue. A feedback sense electrode and a compensation electrode are positioned proximal to the tissue to make electrical contact with the tissue. A feedback amplifier is referenced to ground, and takes as an input a feedback signal from the feedback sense electrode. The output of the feedback amplifier is connected to the compensation electrode. The feedback amplifier thus drives the neural tissue via the compensation electrode in a feedback arrangement which seeks to drive the feedback signal to ground, or other desired electrical value.

Techniques for sensing neural responses such as Evoked Compound Action Potentials (ECAPs) in an implantable stimulator device are disclosed. A first therapeutic pulse phase is followed by a second pulse phase, which phases may be of opposite polarities to assist with active charge recovery. The second pulse phase is formed so as to overlap in time with the arrival of the ECAP at a sensing electrode, which second phase may generally be longer and of a lower amplitude. In so doing, a stimulation artifact formed in a patient's tissue is rendered constant, and of a smaller amplitude, when the ECAP is sensed at the sensing electrode, which eases sensing by a sense amp circuit. Passive charge recovery may follow the second phase, which will not interfere with ECAP sensing that has already occurred.

Embodiments describe herein generally pertain to implantable medical device (IMDs), and methods for use therewith, that can be used to automatically switch an IMD from its normal operational mode to magnetic resonance imaging (MRI) safe mode, and vice versa, within increased specificity. A controller of an IMD is configured to use an accelerometer to determine whether a positional condition associated with a patient is detected, and control sampling of a magnetic field sensor or at least one signal output therefrom, such that a first sampling rate is used when the positional condition is detected, and a second sampling rate, that is slower than the first sampling rate, is used when the positional condition is not detected, to thereby conserve power. Based on results of the sampling, the controller determines whether a magnetic field condition is detected, and in response thereto performs a mode switch to an MRI safe mode.

A catheterization system that includes an electrophysiologic (EP) catheter which has a lumen receiving an electrically conductive fluid delivered by a hydraulic line that is acted upon by a peristaltic pump advantageously avoids noise in intracardiac ECG signal recordings by using an electrical connection to short triboelectrical charge carried by the conductive fluid in the hydraulic line to an existing analog ground in the system. In one embodiment, the electrical connection includes an electrically conductive wire housed in the control handle and configured to provide electrical connection between the fluid and a pin on a printed circuit board housed in the control handle that is electrically connected to the analog ground. In another embodiment, the electrical connection shorts the electrically conductive fluid proximal of the control handle of the catheter.

Systems and methods are described for denoising, or filtering out, unwanted noise or interference, from biological or physiological parameter signals or waveforms such as ECG signals caused by application of electromagnetic energy (e.g., electrical stimulation) in a vicinity of sensors configured to obtain the biological or physiological parameter signals.

A physiological signal of a patient is sensed with sense electrodes symmetrically arranged relative to a stimulation electrode. In some examples, a member includes a plurality of relatively small electrodes that are configured to function as both sense and stimulation electrodes. One or more of the electrodes may be selected as stimulation electrodes and two or more different electrodes of the member may be selected as sense electrodes that are symmetrically arranged relative to the one or more selected stimulation electrodes. In some examples, a member includes a plurality of levels of segmented sense electrodes and a plurality of levels of stimulation electrodes. The levels of sense electrodes are arranged such that each level of stimulation electrodes is adjacent at least two levels of sense electrodes symmetrically arranged relative to the level of stimulation electrodes.

There is described a technique using apparatus for recording and analyzing a surface electrocardiogram (ECG) for distinguishing a physiological signal from noise. The technique involves aligning and averaging multiple surface electrogram records taken for repeated pacing sequence with the same interval between pacing stimuli.