Elevated heart rates recorded from two free-ranging wild black bears. The top panel demonstrates heart rate acceleration from a steady rate of approximately 85 bpm to 214 bpm. The bottom panels shows an acceleration during a period with a pronounced respiratory sinus arrhythmia (RSA). Note that the respiration rate is readily apparent in the lower panel from the RSA (4 breaths/minute; 14 breaths taken over a period of 220 seconds). It is postulated that this elevation in heart rate is due to a deepened breath. A sample of the ECG during the maximum recorded heart rate is inset in each panel (each interval on the ECG strip is equal to 0.2 seconds). The arrow indicates the approximate center point of the ECG strip.
Laske et al. BMC Physiology 2011 11:13 doi:10.1186/1472-6793-11-13