System and method for distinguishing a cardiac event from noise in an electrocardiogram (ECG) signal

Patent metadata

Field	Value
Publication number	US-11160484-B2
Application number	US-201916537917-A
Country	US
Kind code	B2
Filing date	Aug 12, 2019
Priority date	Jul 7, 2014
Publication date	Nov 2, 2021
Grant date	Nov 2, 2021

Abstract

A system includes an ambulatory medical device and a server. The ambulatory medical device comprises: a digital signal processing module configured to: detect an abnormal rhythm from an electrocardiogram (ECG) signal of a patient using a first signal processing routine; and generate a first flag indicating an abnormal rhythm is detected; and a noise detector module configured to: receive the ECG signal from the digital signal processing module; execute a second signal processing routine to classify the abnormal rhythm as one of an arrhythmia event and a noise event; and, if the abnormal rhythm is classified as a noise event, initiate a preconfirmation period during which the noise detector module continues to evaluate the abnormal rhythm and classify the abnormal rhythm as one of an arrhythmia event and a noise event using the second signal processing routine; and generate a second flag indicating the start of the preconfirmation period; and a server configured to: receive the ECG signal, the first flag indicating the abnormal rhythm, and the second flag indicating the start of the preconfirmation period; and provide a visual indication of the preconfirmation period.

First claim

The invention claimed is:

1. A cardiac monitoring and treatment system, comprising:
at least one sensing electrode for obtaining an electrocardiogram (ECG) signal from a patient;
a memory configured to store a history of data and events; and
at least one processor operatively coupled to the at least one sensing electrode, the at least one processor configured to execute a signal processing routine comprising:
a first signal processing routine configured to
analyze the ECG signal from the at least one sensing electrode,
detect an abnormal heart rhythm, and
store the ECG signal in the memory of the system, and

a second signal processing routine configured to
determine a transformed ECG signal comprising at least one of a power spectral density (PSD) and a frequency domain representation of the ECG signal,
extract a plurality of values representing features of the transformed ECG signal,
analyze the plurality of values in a machine learning classifier to determine a score associated with the ECG signal, wherein the machine learning classifier is based on a training data set comprising a collection of ECG signals associated with treatments performed by a plurality of defibrillators,
compare the ECG-derived score to a predetermined threshold score, and
classify the detected abnormal heart rhythm as one of a cardiac event or a noise event in the ECG signal based on the comparison.

2. The system of claim 1 , wherein the plurality of values representing features of the transformed ECG signal comprise at least four features of the PSD representation.

3. The system of claim 2 , wherein the at least four features of the PSD representation that are extracted are: at least one value representing a dominant frequency of the PSD; at least one value representing in-band entropy of the PSD between frequencies of 2 Hz and 6 Hz; at least one value representing first-band entropy of the PSD between frequencies of 0 Hz and 2 Hz; and at least one value representing a variance of the PSD.

4. The system of claim 1 , wherein the detected abnormal heart rhythm is at least one of a ventricular fibrillation (VF) and a ventricular tachycardia (VT).

5. The system of claim 1 , wherein the machine learning classifier is one of a multivariate adaptive regression splines classifier and a neural network classifier.

6. The system of claim 1 , further comprising therapy pads in communication with the at least one processor and being removably connected to the patient, the therapy pads configured to deliver a therapeutic shock to the patient in response to detection of a cardiac event.

7. The system claim 6 , further comprising at least one response mechanism operatively connected to the at least one processor, the at least one response mechanism configured to prevent the delivery of the therapeutic shock in response to a patient actuation of the at least one response mechanism.

8. The system of claim 1 , wherein the second signal processing routine is configured to evaluate a portion of the ECG signal that is stored in the memory, and wherein the portion of the ECG signal evaluated is a predetermined time period of the ECG signal that precedes the detection of the abnormal heart rhythm.

9. The system of claim 8 , wherein the predetermined time period is 20 seconds.

10. The system of claim 1 , further comprising a communications module configured to report data and events stored by the memory to a central location.

11. The system of claim 1 , wherein the first signal processing routine is further configured to record an event flag associated with the stored ECG signal indicative of the abnormal heart rhythm.

12. The system of claim 1 , wherein the second signal processing routine is further configured to initiate a pre-confirmation period during which the second signal processing routine continues to
evaluate the abnormal heart rhythm and classify the abnormal heart rhythm as one of an arrhythmia event and a noise event, and
does not provide an alert to the patient regarding the abnormal heart rhythm.

13. The system of claim 12 , wherein the second signal processing routine is further configured to generate a second flag indicating the initiation of the pre-confirmation period.

14. The system of claim 12 , further comprising a communications circuitry configured to transmit the stored ECG signal to a server at a central location.

15. The system of claim 14 , further comprising the server at the central location, wherein the server is further configured to provide to a remote device operative connected to the server a visual representation of the ECG signal, along with one or more annotations of a portion of the ECG signal corresponding to the pre-confirmation period.

16. The system of claim 15 , wherein the pre-confirmation period is highlighted by providing a portion of the visual representation of the ECG signal corresponding to the pre-confirmation period a color that is different than a remainder of the visual representation of the ECG signal.

17. The system of claim 15 , wherein the pre-confirmation period is indicated by providing a portion of the visual representation of the ECG signal corresponding to the pre-confirmation period with at least one of icons and text to differentiate the portion from a remainder of the visual representation of the ECG signal.

18. The system of claim 15 , wherein the visual representation of the ECG signal further comprises icons and text providing further information comprising at least one of a patient's heart rate and a threshold VT heart rate.

19. The system of claim 15 , wherein the pre-confirmation period is between about 10 seconds and about 60 seconds.

20. The system of claim 15 , wherein the server is configured to provide the visual representation of the ECG signal to the remote device through an online portal.

21. The system of claim 15 , wherein the server is configured to generate a report comprising the visual representation of the ECG signal, along with one or more annotations of a portion of the ECG signal corresponding to the pre-confirmation period.

Assignees

• Zoll Medical Corp

Inventors

• Sullivan Adam
• Kaib Thomas E
• Nicolo Francesco
• Szymkiewicz Steven J
• Whiting Jason T

Classifications

• A61B5/349 Primary

  Detecting specific parameters of the electrocardiograph cycle · CPC title

• A61N1/046

  Specially adapted for shock therapy, e.g. defibrillation · CPC title

• A61B5/6802

  Sensor mounted on worn items · CPC title

• A61B5/316 Primary

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

• A61B5/333

  Recording apparatus specially adapted therefor · CPC title