How to Filter Data and Correct Artifacts in AcqKnowledge
Steps
Steps for an inverted QRS wave:
-
Open AcqKnowledge
-
Select “analyze only” and then click “ok” on the pop-up menu
-
Change the file type to txt file, select your ECG file, and then click “open”
-
Enter your sampling rate in milliseconds/sample for the sampling rate interval (250 Hz will be 4 ms/s) and click “ok”
-
Go to “transform” -> “expression” and then enter “-CH0” into the box and click “ok”
-
Minimize CH0 by clicking on the drop-down arrow in the left hand corner of the channel
-
Click on CH1, resize the channel by entering ctrl+y.
-
Relabel the left side of the channel with “ECG” and the right hand side with “mV”
-
To filter the data, go to “transform” -> “digital filters” -> “comb band stop” and click “ok”
Steps for a normal QRS wave:
-
Open AcqKnowledge
-
Select “analyze only” and then click “ok” on the pop-up menu
-
Change the file type to txt file, select your ECG file, and then click “open”
-
Enter your sampling rate in milliseconds/sample for the sampling rate interval (250 Hz will be 4 ms/s) and click “ok”
-
Relabel the left side of the channel with “ECG” and the right hand side with “mV”
-
To filter the data, go to “transform” -> “digital filters” -> “comb band stop” and click “ok”
After filtering:
-
Resize the dataset by going to “auto scale” and then entering ctrl+y
-
Scan for artifacts
-
Zoom in on artifacts using the zoom tool
-
To correct a missed QRS peak, take the I-beam tool and highlight from one end of the peak to the next.
-
Go to “transform” -> “waveform math”
-
Make sure that
-
Source 1 = the channel you are on
-
Addition is selected
-
Source 2 = K, a constant
-
Destination = the channel you are on
-
-
Enter a constant to add to the waveform and click “ok”
-
-
To correct noise that could interfere with QRS detection, highlight from the end of one QRS peak to the start of the next QRS peak using the I-beam tool.
-
Go to “transform” -> “math functions” -> “connect endpoints”
-
-
Repeat this process for any artifacts. Be sure to scan the entire waveform for artifacts before exporting.
-
Remove any extraneous channels (otherwise these will be exported with the corrected channel) by selecting the channel you want to remove, and going to “edit” -> “remove waveform”.
-
Then, once you are ready to export go to “file” -> “save as” and select txt file from the file type menu. Name your file, then click “save” and then “ok”