Biomedical User Group Documents
The ECG Feature Extractor allows you to extract ECG features from an ECG signal, such as the QRS complex and P and T waves. The input signal can be loaded from a file or acquired from a DAQ device. When you use a DAQ device, the ECG Feature Extractor can perform online analysis.
New features in the 2013 ECG Feature Extractor
- ST segment analysis
- New algorithm, providing more accurate feature extraction results
- Modify the feature extraction results and save them to file
- Load feature extraction results from previously saved file
- Display annotations on graph
New Feature Settings Dialog Box
The Feature Settings dialog box has been redesigned for the new algorithm. In the QRS Detection section, you can set the QRS frequency, QRS onset and QRS offset according to the QRS wave type of your signal. In the P/T Wave Refinement section, you now have the option to remove the noise from a raw signal by low-pass filtering. Set the PR interval and QT interval to configure how the application refines the P wave and the T wave.
New ST segment analysis
In this version, the ECG Feature Extractor provides ST analysis. You can find the ST segment information in the Statistics window, by clicking Statistics on the main window, or in the Beat Characteristics window, by right-clicking on the graph and selecting Show and Modify Beat Characteristics....
Modify the Feature Extraction Results
You can now modify the results if the automated feature extraction results are not optimal.
Note: You can only modify results in file mode.
Modify a Beat
After the feature extraction completes, right-click on the beat that you want to modify and select Show and Modify Beat Characteristics... to open the Beat Characteristics window.
In this window, drag the annotations on the graph to modify the position of feature points. The other beat characteristics will be automatically updated. You can click Zoom in and Zoom out to change the window size.
When Detect QRS complex only is unchecked in Feature Settings, you can right-click on the graph and select P Wave Valid or T Wave Valid to specify whether this beat contains a valid P wave or T wave.
Click Apply to apply the changes you have made to the current beat. You can click << or >> to view and modify the previous beat or the next beat.
Delete a Beat
To delete a beat, click Delete on the Beat Characteristics window. You can also right-click on the beat that you want delete on the main window and select Delete Beats... and then select to delete all beats or delete the current beat.
Add a Beat
To add a new beat, right-click on the area where you want to add a beat on the main window and select Add Beat Manually.... The Beat Characteristics window will automatically open. You can then modify the added beat.
Note: You must right-click on a blank area (where no red or green segment exists), because the added beat cannot overlap with an existing beat.
Save Feature Extraction Results
To save feature extraction results, you need to first configure the feature settings. In the Feature Settings dialog box, select Log signals and save feature extraction results to file and then specify a file path (TDMS file). You also can specify an Annotation tag to write the feature extraction results as annotations. When you load ECG signals from a TDMS file created by the LabVIEW Biomedical Toolkit, you can also select Save to original file to save the annotations to the original file.
After configuring the feature settings, click Start to save the features extraction results. If you want to save the results after you manually modify them, you need to click Save on the main window.
Display Annotations and Load Feature Extraction Results from Annotations
If an ECG file contains annotations, you can now view them in the ECG Feature Extractor. Click Ann after you load the file. The Configure Annotations dialog box will appear. The Show annotations section lists the available annotation tags. You can select one or more tags and then click OK. The selected annotations show on the main window.
If a file contains annotations previously written by the ECG Feature Extractor, you can load the corresponding feature extraction results from the annotations. In order to do this, you need to select Load ECG features from annotation in Configure Annotations dialog box and then select an annotation tag to load.
