Graphical plots of beat-by-beat heart rate (HR) patterns, e.g., Poincare?? plots, provide information beyond traditional HRV, but such plots have not been used in mice. HR patterns from 3 min recording/ hour in 4 wild type and 4 PGC1??-deficient mice were compared. In comparison to normal mice, knockout mice tended to have lower HRs (694 ?? 16 vs. 752 ?? 51 bpm) consistent with their decreased ability to use glucose in the heart. Poincare?? plots from each hour showed that none of the wild-type mice had abnormal, fan-like, complex patterns in any hour of their recording. However, 3 of the 4 knockout mice had a complex pattern in at least 10 hours of the recording. Results suggest that hourly Poincare?? plot analyses from multiple short-term recordings may be useful in identifying cardiac autonomic abnormalities in knockout mouse models. Samples from the entire 24-hour period provide more information about autonomic function than a single brief recording.