Medical device and method for detecting electrical signal noise

Patent metadata

Field	Value
Publication number	US-11737712-B2
Application number	US-202016874920-A
Country	US
Kind code	B2
Filing date	May 15, 2020
Priority date	May 15, 2020
Publication date	Aug 29, 2023
Grant date	Aug 29, 2023

Abstract

A medical device is configured to sense event signals from a cardiac electrical signal and determine maximum amplitudes of cardiac electrical signal segments associated with sensed event signals. The medical device is configured to determine at least one tachyarrhythmia metric based on at least a greatest one of the determined maximum amplitudes. The medical device may determine when the at least one tachyarrhythmia metric does not meet true tachyarrhythmia evidence and, in response, determine when the maximum amplitudes meet suspected noise criteria. The medical device may withhold a tachyarrhythmia detection and tachyarrhythmia therapy when suspected noise criteria are met.

First claim

What is claimed is:

1. A medical device comprising:
a sensing circuit configured to sense at least one cardiac electrical signal and sense event signals from the at least one cardiac electrical signal; and
a control circuit coupled to the sensing circuit and configured to:
determine a maximum amplitude associated with each of a plurality of the sensed event signals;
identify a greatest maximum amplitude from the determined maximum amplitudes associated with the plurality of the sensed event signals;
determine at least one tachyarrhythmia metric based on at least the identified greatest maximum amplitude;
determine the at least one tachyarrhythmia metric does not meet true tachyarrhythmia evidence criteria;
determine that suspected noise criteria are met based on the determined maximum amplitudes;
determine that a tachyarrhythmia detection criterion is met based on event signals sensed by the sensing circuit; and
in response to determining that the true tachyarrhythmia evidence criteria are not met and that the suspected noise criteria are met, withhold a tachyarrhythmia detection when the tachyarrhythmia detection criterion is determined to be met.

2. The device of claim 1 , wherein the control circuit is configured to:
set a threshold amplitude based on the greatest maximum amplitude;
identify each of the maximum amplitudes that are greater than the threshold amplitude;
determine the at least one tachyarrhythmia metric by determining a suspected true event interval based on each of the maximum amplitudes identified to be greater than the threshold amplitude; and
determine that the at least one tachyarrhythmia metric does not meet true tachyarrhythmia criteria by determining that the suspected true event interval does not fall within a predetermined interval range.

3. The device of claim 1 , further comprising a memory configured to buffer a cardiac electrical signal segment in response to each of the plurality of the sensed event signals;
wherein the control circuit is configured to:
determine at least one tachyarrhythmia metric by determining at least one gross morphology metric from the buffered cardiac electrical signal segment associated with the greatest maximum amplitude;
determine that the at least one tachyarrhythmia metric does not meet true tachyarrhythmia evidence criteria by determining that the at least one gross morphology metric is less than or equal to a threshold.

4. The device of claim 3 , wherein the control circuit is configured to determine the at least one gross morphology metric by:
determining a summation of absolute amplitudes of sample points of the buffered cardiac electrical signal segment;
determining a maximum absolute amplitude of the buffered cardiac electrical signal segment; and
determining the at least one gross morphology metric by dividing the summation of sample points by the maximum absolute amplitude.

5. The device of claim 3 , wherein the control circuit is configured to determine the at least one gross morphology metric by determining a maximum pulse width of the buffered cardiac electrical signal segment.

6. The device of claim 3 , wherein the control circuit is configured to:
determine at least one gross morphology metric by determining a gross morphology amplitude metric from the buffered cardiac electrical signal segment associated with the greatest maximum amplitude and determining a gross morphology signal width metric from the buffered cardiac electrical signal segment associated with the greatest maximum amplitude; and
determine the at least one tachyarrhythmia metric does not meet true tachyarrhythmia criteria by determining that at least one of the gross morphology amplitude metric is less than or equal to a first threshold or the gross morphology signal width metric is less than or equal to a second threshold.

7. The device of claim 1 , wherein:
the sensing circuit is configured to:
sense a first cardiac electrical signal and a second cardiac electrical signal; and
sense event signals from the first cardiac electrical signal; and

the control circuit is configured determine the maximum amplitudes and the at least one tachyarrhythmia metric from the second cardiac electrical signal.

8. The device of claim 7 , wherein:
the sensing circuit comprises:
a narrowband filter having a first bandpass for sensing the first cardiac electrical signal;
a wideband filter having a second bandpass wider than the first bandpass for sensing the second cardiac electrical signal; and
a notch filter for filtering the second cardiac electrical signal;

the control circuit is configured to determine the maximum amplitude associated with each of the plurality of the sensed event signals by determining a maximum peak to peak amplitude of the notch filtered second cardiac electrical signal.

9. The device of claim 1 , wherein the control circuit is configured to determine that suspected noise criteria are met based on the determined maximum amplitudes by determining that at least one of the maximum amplitudes is less than a noise threshold amplitude.

10. The device of claim 1 , wherein the control circuit is configured to determine that suspected noise criteria are met based on the determined maximum amplitudes by determining that a ratio of a lowest maximum amplitude determined from the maximum amplitudes to a greatest maximum amplitude determined from the maximum amplitudes is less than a threshold ratio.

11. The device of claim 1 , wherein:
the sensing circuit comprises a notch filter for filtering at least one cardiac electrical signal;
the control circuit is configured to determine that suspected noise criteria are met based on the determined maximum amplitudes by:
determining a first maximum amplitude from the at least one cardiac electrical signal;
determining a second maximum amplitude from the at least one cardiac electrical signal after notch filtering;
determining a ratio of the second maximum amplitude to the first maximum amplitude;
determining that the ratio is less than a relative noise threshold.

12. The device of claim 1 , further comprising a therapy delivery circuit configured to deliver a tachyarrhythmia therapy, wherein:
the control circuit is further configured to detect tachyarrhythmia by:
determining that the tachyarrhythmia detection criterion is met based on event signals sensed by the sensing circuit; and
determining that at least one of:
the true tachyarrhythmia evidence criteria are met by the at least one tachyarrhythmia metric; or
the suspected noise criteria are not met by the maximum amplitudes; and

the therapy delivery circuit is configured to deliver a therapy in response to the control circuit detecting the tachyarrhythmia.

13. A method, comprising:
sensing at least one cardiac electrical signal;
sensing event signals from the at least one cardiac electrical signal;
determining a maximum amplitude associated with each of a plurality of the sensed event signals;
identifying a greatest maximum amplitude from the determined maximum amplitudes associated with the plurality of the sensed event signals;
determining at least one tachyarrhythmia metric based on at least the identified greatest maximum amplitude;
determining the at least one tachyarrhythmia metric does not meet true tachyarrhythmia evidence criteria;
determining that suspected noise criteria are met based on the determined maximum amplitudes;
determining that a tachyarrhythmia detection criterion is met based on the plurality of sensed event signals; and
in response to determining that the true tachyarrhythmia evidence criteria are not met and that the susp

Assignees

• Medtronic Inc

Inventors

• Greenhut Saul E
• Liu Yuanzhen
• Zhang Xusheng

Classifications

• A61B5/346

  Analysis of electrocardiograms · CPC title

• A61B5/33

  specially adapted for cooperation with other devices · CPC title

• A61B5/7203 Primary

  for noise prevention, reduction or removal · CPC title

• A61B5/316

  Modalities, i.e. specific diagnostic methods · CPC title

• A61B5/363

  Detecting tachycardia or bradycardia · CPC title