Fig. 2.

Overview of zebrafish ECG reading GUI (zERG), a zebrafish ECG analysis software program. In step 1, ECG voltage measurements are imported into zERG. In step 2, data for peak analysis are selected. During peak analysis, P waves (red asterisks) and QRS complexes (black asterisks) are identified based on the following: (1) the user-defined wave amplitude threshold; (2) the minimum peak distance; and (3) classification based on the distance between the P peak to R wave of consecutive cycles and the reference distance defined as two times the first ‘P peak to R wave’ interval. Consecutive red or black peaks are marked yellow for error correction; the user can then manually add and/or delete P waves and/or QRS complexes. Once all waves are marked correctly, the user can proceed to step 3 by choosing the ‘Calculate Average Trace’ button. This plots an average trace and allows the user to click on ‘Add Markers’ to note wave markers on the average trace. Finally, after all peaks are confirmed, the user selects ‘Analyze ECGs’ to obtain a graphical user interface (GUI) table with the ECG metrics, in addition to an output .txt and several average trace plots. The yellow boxes show an example of a trace in which the P wave amplitude exceeds the R wave amplitude and how zERG handles such traces. The example trace in the blue boxes was captured from a 6-month-old AB wild-type male fish, and the trace in the yellow boxes was captured from a 3.5-month-old AB wild-type male fish after being dosed with 0.800 mmol/l FA for 15 min. All images were captured from zERG version 1.0.