Electrocardiogram signal detection

Patent metadata

Field	Value
Publication number	US-9254095-B2
Application number	US-201314076076-A
Country	US
Kind code	B2
Filing date	Nov 8, 2013
Priority date	Nov 8, 2012
Publication date	Feb 9, 2016
Grant date	Feb 9, 2016

Abstract

Apparatuses and methods for extracting, de-noising, and analyzing electrocardiogram signals. Any of the apparatuses described herein may be implemented as a (or as part of a) computerized system. For example, described herein are apparatuses and methods of using them or performing the methods, for extracting and/or de-noising ECG signals from a starting signal. Also described herein are apparatuses and methods for analyzing an ECG signal, for example, to generate one or more indicators or markers of cardiac fitness, including in particular indicators of atrial fibrillation. Described herein are apparatuses and method for determining if a patient is experiencing a cardiac event, such as an arrhythmia.

First claim

What is claimed is:

1. A non-transitory computer-readable storage medium storing a set of instructions capable of being executed by a processor, that when executed by the processor, causes the processor to extract an electrocardiogram (ECG) signal from a signal containing noise by causing the processor to:
identify putative QRS regions in the signal containing noise;
cross-correlate the putative QRS regions to determine correlated QRS regions in the signal containing noise;
de-noise the correlated QRS regions by filtering correlated QRS regions in the signal containing noise using a first filtering regime, wherein the correlated QRS regions are filtered by the first filtering regime in isolation of the entire signal containing noise, and filtering a remainder of the signal containing noise outside of the correlated QRS regions using a second filtering regime that is different from the first filtering regime;
construct a de-noised ECG signal comprising the filtered correlated QRS regions and the filtered remainder of the signal outside of the correlated QRS regions; and
present the de-noised ECG signal.

2. The non-transitory computer-readable storage medium of claim 1 , wherein the set of instructions, when executed by the processor, further causes the processor to:
identify putative R-R intervals in the de-noised ECG signal;
cross-correlate the putative R-R intervals to determine correlated R-R intervals in the de-noised ECG signal; and
modify the de-noised ECG signal by filtering only the correlated R-R intervals of the de-noised ECG signal with a third filtering regime.

3. The non-transitory computer-readable storage medium of claim 2 , wherein the set of instructions causes the processor to identify putative R-R intervals in the de-noised ECG signal by constructing an R-R matrix of normalized R-R intervals from the de-noised ECG signal.

4. The non-transitory computer-readable storage medium of claim 3 , wherein the set of instructions causes the processor to cross-correlate the putative R-R intervals to determine correlated R-R intervals in the de-noised ECG signal by cross-correlating every normalized R-R interval in the R-R matrix against every other normalized R-R interval in the matrix.

5. The non-transitory computer-readable storage medium of claim 4 , wherein the set of instructions causes the processor to determine correlated R-R intervals when a correlation coefficient threshold between R-R intervals is above an R-R correlation threshold.

6. The non-transitory computer-readable storage medium of claim 5 , wherein the R-R correlation coefficient threshold is about 0.7.

7. The non-transitory computer readable storage medium of claim 5 , wherein the set of instructions causes the processor to modify the de-noised ECG signal by filtering only the correlated R-R intervals of the de-noised ECG signal with a Principle Component Analysis (PCA) of the correlated R-R intervals.

8. The non-transitory computer-readable storage medium of claim 1 , wherein the set of instructions, when executed by the processor, further causes the processor to pre-filter the signal containing noise before identifying putative QRS regions in the signal containing noise.

9. The non-transitory computer-readable storage medium of claim 1 , wherein the set of instructions, when executed by the processor, further causes the processor to remove 50 Hz or 60 Hz noise in the signal containing noise before identifying putative QRS regions in the signal containing noise.

10. The non-transitory computer-readable storage medium of claim 1 , wherein the set of instructions, when executed by the processor, further causes the processor to perform wavelet filtering on the signal containing noise before identifying putative QRS regions in the signal containing noise.

11. The non-transitory computer-readable storage medium of claim 1 , wherein the set of instructions causes the processor to identify putative QRS regions in the signal containing noise by filtering the signal, setting a threshold, and identifying spikes above the threshold as putative R-spike components of putative QRS regions.

12. The non-transitory computer-readable storage medium of claim 11 , wherein the set of instructions, when executed by the processor, further causes the processor to calculate a putative heart rate (HR) from the R-spikes and to use the HR to modify the signal containing noise to remove baseline wander.

13. The non-transitory computer-readable storage medium of claim 1 , wherein the set of instructions causes the processor to cross-correlate the putative QRS regions to determine correlated QRS regions of the signal containing noise by cross-correlating each putative QRS region with every other putative QRS region.

14. The non-transitory computer-readable storage medium of claim 1 , wherein the set of instructions causes the processor to determine correlated QRS regions of the signal containing noise when a peak correlation between a pair of putative QRS regions is above a correlation threshold and their amplitudes vary by less than an amplitude threshold.

15. The non-transitory computer-readable storage medium of claim 14 , wherein the correlation coefficient threshold is about 0.8 and the amplitude threshold is about 40%.

16. The non-transitory computer-readable storage medium of claim 1 , wherein the set of instructions, when executed by the processor, further causes the processor to indicate that there may be a problem with the signal containing noise when there are fewer than a minimum number of correlated consecutive putative QRS regions.

17. The non-transitory computer-readable storage medium of claim 16 , wherein the minimum number of correlated consecutive putative QRS regions is 6.

18. The non-transitory computer-readable storage medium of claim 1 , wherein the set of instructions causes the processor to construct the de-noised ECG signal from the signal by removing the correlated QRS regions from the signal containing noise to form a subtracted signal, filtering the correlated QRS regions of the signal using the first filtering regime and filtering the subtracted signal comprising the remainder of the signal outside of the correlated QRS regions using the second filtering regime, and then adding together the filtered correlated QRS regions with the filtered subtracted signal.

19. The non-transitory computer-readable storage medium of claim 1 , wherein the set of instructions causes the processor to construct the de-noised ECG signal from the signal by filtering the correlated QRS regions of the signal using the first filtering regime comprising a Principle Component Analysis (PCA).

20. The non-transitory computer-readable storage medium of claim 1 , wherein the set of instructions causes the processor to construct the de-noised ECG signal from the signal by filtering the remainder of the signal outside of the correlated QRS regions using the second filtering regime comprising a polynomial fit to the remainder of the signal outside of the correlated QRS regions.

21. The non-transitory computer-readable storage medium of claim 1 , wherein the set of instructions causes the processor to present the de-noised ECG signal by displaying the de-noised ECG signal.

22. The non-transitory computer-readable storage medium of claim 1 , wherein the set of instructions, when executed by the processor, further causes the processor to determine if the signal is indicative of an atrial fibrillation.

23. The non-transitory

Assignees

• Alivecor Inc
• Alivecor

Inventors

• Galloway Conner Daniel Cross
• Albert David E

Classifications

• A61B5/7203 Primary

  for noise prevention, reduction or removal · CPC title

• A61B5/02438

  with portable devices, e.g. worn by the patient · CPC title

• A61B5/0006

  ECG or EEG signals · CPC title

• A61B5/358

  Detecting ST segments · CPC title

• A61B5/353

  Detecting P-waves · CPC title