Although the Spike Histogram Module
for LabChart was initially designed to discriminate extracellular neural spike activity, the pattern matching features can be used to detect specific waveform shapes within any kind of data. To use Spike Histogram to detect arrhythmia shapes within an ECG waveform, first set up the detector by accessing the Settings
dialog within the Spike Histogram menu. Use a detection threshold that will find both normal and abnormal ECG beats, and be sure to use trigger intervals long enough to include the entire ECG heartbeat.
Next, open the Discriminator from the Spike Histogram menu in LabChart. Note that there should be two main clusters of beats on the left side of the Discriminator plot; one group of normal ECG beats, and one group of arrhythmic beats. When you click on individual beats (marked by x's) on the left side of the Discriminator, the selected waveform will be highlighted in black on the right side of the Discriminator. You can mark a group of beats "arrhythmic" by drawing a circle around the beats on the left side corresponding to an arrhythmia shape on the right side (see the red circle in the left side of the Discriminator below) and clicking "Add Unit."
After adding the unit of arrhythmic beats in the Discriminator, the instances of arrhythmia in the Chart View will each be marked by a red dot.
If desired, you can then use the Spike Histogram channel calculation to track instantaneous frequency or create a spike at every occurrence.
If you are displaying Unit Spikes, you can then use the Cyclic Measurements channel calculation in a new channel to keep a running count of the arrhythmia events by selecting Cyclic Measurements from the new channel's menu and choosing the Count calculation with the unit spikes channel as the source.
A LabChart file demonstrating the use of Spike Histogram to detect arrhythmias and add arrhythmia information to the Data Pad
can be downloaded HERE