Method and system for noise measurement in an implantable cardiac device
AssigneeCardiac Pacemakers, Inc.
InventorsSurekha Palreddy, Carlos Ricci, Yayun Lin
Life of this patent
Estimating the term…
Abstract
An implantable cardiac rhythm management device is configured to estimating the noise level and noise floor in a sensing channel by measuring the magnitude of signal in the sensing channel when noise is determined to be present or absent, respectively. The presence or absence of noise may be determined by computing the density of local peaks or inflection points in an electrogram waveform. The computed local peak density is then used to set or clear a noise flag, which signifies whether noise is present or not. A noise statistic computed from samples of the electrogram signal obtained through a sensing channel may then be used to estimate a noise level or a noise floor.
Claims25
A method for operating a cardiac rhythm management device, comprising:
- sampling an electrogram signal from a sensing channel of the device to obtain a series of samples, where each sample can be designated by X[n] with n an integer;
- determining whether each sample represents a local peak or not, wherein a sample X[n] is a local peak if its amplitude is either:
- 1) greater than the amplitude of the preceding sample X[n−1] by a specified threshold value δ1 and also greater than the amplitude of the subsequent sample X[n+1] by the specified threshold δ2, or 2) less than the amplitude of the preceding sample X[n−1] by a specified threshold δ3 and also less than the amplitude of the subsequent sample X[n+1] by the specified threshold δ4;
- computing a local peak density in a predetermined number of consecutive samples;
- computing a noise flag as either set or cleared in accordance with the computed local peak density, wherein the noise flag is set if the local peak density exceeds a first threshold value;
- and,
- estimating a noise level in the electrogram signal by computing a noise statistic from a series of samples when the noise flag is set.
21 The method of claim 3 further comprising adjusting a sensing threshold or threshold profile of a sensing amplifier in accordance with the estimated noise floor when the noise flag is cleared.
The method of claim 21 wherein the sensing threshold, a starting value, decay rate, or sensing floor of the threshold profile, is adjusted by multiplying its nominal value by a coefficient and then adding an offset value to the result, where the offset value and coefficient value are based upon the estimated noise floor.
A cardiac rhythm management device, comprising:
- one or more sensing channels for sensing intrinsic cardiac activity;
- means for sampling an electrogram signal from a sensing channel of the device to obtain a series of samples, where each sample can be designated by X[n] with n an integer;
- means for determining whether each sample represents a local peak or not, wherein a sample X[n] is a local peak if its amplitude is either:
- 1) greater than the amplitude of the preceding sample X[n−1] by a specified threshold value δ1 and also greater than the amplitude of the subsequent sample X[n+1] by the specified threshold δ2, or 2) less than the amplitude of the preceding sample X[n−1] by a specified threshold δ3 and also less than the amplitude of the subsequent sample X[n+1] by the specified threshold δ4;
- means for computing a local peak density in a predetermined number of consecutive samples;
- means for computing a noise flag as either set or cleared in accordance with the computed local peak density, wherein the noise flag is set if the local peak density exceeds a first threshold value;
- and,
- means for estimating a noise level in the electrogram signal by computing a noise statistic from the series of samples when the noise flag is set.
Dependencies are inferred from the claim text.