Detection of Atrial Fibrillation in mice with Ponemah 5.4
Atrial Fibrillation (AFib) is characterized by disorganized atrial electrical activity and contraction.
During AFib, the heart rate is irregular, and there are no P-waves.
The method described below only relies on changes in heart rate to identify potential regions of AFib. P waves were not used since they are often not reliably identified. If clearly defined P waves are available, the absence of P-waves can be incorporated into these searches.
Ensure the ECG signal is well marked
- Use the following Data Insights (DI) searches to identify and correct marking errors:
- dv_HR Change
- dv_HR Limits
- dv_HR Missed Beats
- Missed beats and triggering on noise can introduce variability in the heart rate that is misinterpreted by the search
- In the case of missed beats an option would be to discard results where the HR or beat to beat HR change fell outside of a defined range but cleaning up the data is the preferred method.
Create new Custom Derived Parameters to detect high heart rate variability
- Changes in heart rate are evaluated over a range of beats to account for the inherent variability during an AFib event and to group adjacent AFib events that may be separated by a few sinus beats
- The selected Standard Deviation (SD) range is used to construct Custom Derived Parameters (CDP) that are used in AFib DI searches
- The attached file (HRSD.XML) can be imported through the CDP dialog to add 6 CDPs with standard deviations over 2 through 9 cycles (HRSD2, HRSD3, HRSD4, HRSD5, HRSD7, HRSD9)
- HRSDx, x represents the number of cycles over which the SD is calculated. Additional CDPs can be constructed if needed.
Create Data Insights Searches
- The CDP HRSD4 has been used in the searches in this example – and will close a gap of up to 3 beats will low HR change. A different CDP may be used based on the SD range selected.
- Two searches are used, _HRSD4 and _HRSD4_series. The two searches can be imported using the attached file (HRSD4_Searches.XML)
- Value(HRSD4cyc0) >= 25
- This identifies beats where the CDP HRSD4 exceeds a threshold (25 bpm)
- The threshold of 25 bpm was selected based on the two datasets provided and was set slightly above the SD of non AFib mice
- Series(_HRSD4, 1) >= 9
- This identifies cycles where 9 or more cycles satisfy the _HRSD4 search
- The number 9 can be increased to only identify longer AFib runs, alternatively the search results can be sorted by the number of cycles in the Series
- Smaller runs of AFib can be identified by decreasing 9 or by creating another Series based search that looks for a specific number of consecutive cycles that match _HRSD4
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