Limitations of power-spectrum and time-domain analysis of heart rate variability in short-term ECG recorded using telemetry in unrestrained rats

A radio-telemetry technique used to record electrophysiological signals in animals is broadly used in experimental studies. Using implantable probes, this technique can record electrocardiographic (ECG) signals without disturbing animal activities. In this study, we investigated the stability of heart rate variability (HRV) parameters computed from radio-telemetry ECG recordings in unrestrained rats. The experiment involved 4 normal rats in which ECGs were recorded during baseline conditions with and without drug-induced autonomic blockade. The study revealed that the stability of HRV estimators for both time and frequency domain analysis in unrestrained rats was highly dependent on the average heart rate (related to physical rats activity) as well as the length of the ECG recording.