How to dect the ECG artifacts by get ECG( ECG=ECG1-ECG2)

Discussions
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1

Hi,
I wanna to consult a issue about applying SSP to remove cardiac artifacts. After linking to the raw files, I have two channels named ECG1 and ECG2 as shown the left panel of screenshot. and I wanna to get the ECG = ECG1- ECG2 signal. I firstly detect the cardiac using the menu as shown the right panel of screenshot. But only can choose ECG1 or ECG2, couldn’t enter ECG=ECG1-ECG2. How should I do to solve this issue? I’m stuck in the data preprocessing step. Thank you so much.

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2

Hi @weixy35, from the plots you shared, it seems the signal on EGC1 is enough to identify the hear beat occurrences, which is all you need to use SSP to remove cardiac artifacts.

3

Thank you, Raymundo. The plots Ushared is easy to recognize. however, there are some other plots that hard to distinguish like following screeshots. I also have EOG signals need to be EOG=EOG1-EOG2. Do you have any solution could solve this? Or I use the ECG1 to calculate SSP one time, and use the ECG2 to calculte SSP again? Is it reasonable?

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4

Hi， Raymundo.
I notice that there is another weird issue. I have several subjects. For the subjects that I didn’t applied the SSP, but when I double click the raw file , choose Artifacts-- select active projectors, it automatically appears the ssp results I did in 10 th of October, Do you know what happened?

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5

You can pre-proccess your raw file to replace the differential channels:

  1. Check the indices for ECG1 and ECG2, this is the first column in the Channel Editor (right-click on the channel file). Let's name these indices ix_ECG1 and ix_ECG2

  2. Run the process Pre-process > Run Matlab command on your raw data, to replace the ECG1 timeseries with the difference ECG-ECG2:

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    Data(ix_ECG1, :) = Data(ix_ECG1, :)- Data(ix_ECG2, :);

  3. A new raw folder will be added to your database with the suffix _matlab, in this one, ECG1 is the difference ECG-ECG2. You can find the heart beats in this channel

6

As SSP projectors are saved in the channel file. These SSP projectors are there because:

  • they were computed before for that recording
  • the channel file was copied from other folder with SSP projectors

You may want to make larger that window to check the date and time when they were created, that may give you a hint of their origin

7

Thank you so much, Raymundo. you really help me solve a big problem!

8

Hi，Raymundo.After I tried your suugestion about the ECG, I replaced their name, and followed by your suggestion, but it got errors as the screenshots. Did you try successfully?

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9

Hi @weixy35, let me clarify the mentioned steps, and use your ECG signal as example:

With this step, I meant to write down the indices of the channels for the pair of sensors that make ECG. From your screenshot it means 34 and 35.

Replace ix_ECG1 and ix_ECG2 with the obtained indices in step 1
Data(34, :) = Data(34, :)- Data(35, :);

10

Thank you. Raymundo. It works!