EP Workbench – Electroanatomic map annotation
This tutorial will show how EP Workbench can be used to edit and annotate electroanatomic maps.
To begin, go to File>>Load>>OpenEP and load your OpenEP file which should be in “.mat” format.
Begin by inspecting the electroanatomic map and its geometry. The default map shown will be a voltage map with colour bar limits set from 0-2. The Field and Colour bar limits can be edited.
- Remove areas of false Geometry
If you notice areas of false geometry, you can use the “geodesic cutter” and “fill holes” tools to edit these. See below an area of false geometry.
Then go to “Tools>>Mesh Editor>>Geodesic cutter” to delete the region
Then use the Fill holes function to refill the mesh.
- Clipping valves and veins
To clip valves, review the area with the valve is for areas of low voltage and for ventricular far field EGMs. Then use the Geodesic cutter to select the region and clip the valve.
This tool can also be used to clip veins as shown below.
Then you will have a mesh with the valves and veins clipped.
- Use the pre-processing tab to remove erroneous points
Toggle “Remove/Restore mapping points where LAT is -10000” to On. Deleted points will be highlighted in yellow.
Use the “Remove/Restore mapping points outside of mesh by distance of X mm” to remove additional points. Notice here that more points are now in yellow indicating that they have been deleted.
- Manually reviewing electrogram points
To review individual electrogram points, switch to the Preferences tab and set the scroll speed to 1. Click apply.
Then switch to the signals tab and manually review use the electrogram points. The window of interest is demarcated by the dashed white lines. The dashed pink line indicates the system identified local activation time. The image below shows a map created under Coronary Sinus pacing at a cycle length of 500ms. A mid coronary site is selected as the Reference channel. These sites can be adjusted in EP Workbench.
The size of the signal can be altered by clicking on it and then using the mouse scroller. Notice the difference in size of the Bipolar signal
To remove erroneous electrogram signals, review the maps and individual electrogram points which appear incorrect for areas which appear incorrect. To remove a point, right click it in the Mapping points box. It will then move to the Recycle bin.
When you have finished annotating the map, go to File> Export>(map name).
This provides a series of options which will enable you to export your data.
You can then edit the map further if you want to create different versions of the data. In the example below, the left atrial appendage has also been clipped. The points associated with the left atrial appendage have also been removed through use of the the pre-processing tab to restore and then re-remove the mapping points outside of the mesh.
