In chronobiology, an<unk>  is a rhythm with a period longer than the period of a circadian rhythm, i.e., with a frequency of less than one cycle in 24 hours. Some examples of<unk> s in mammals include menstruation, breeding, migration, hibernation, molting and fur or hair growth, and tidal or seasonal rhythms. In contrast, ultradian rhythms have periods shorter than the period of a circadian rhythm. Several<unk> s are known to be caused by hormone stimulation or exogenous factors. For example, seasonal depression, an example of an<unk>  occurring once a year, can be caused by the systematic lowering of light levels during the winter.
Infradian rhythm
Ultradian rhythm
Ventricular escape beat
Junctional rhythm
Spike-and-wave
Electrical alternans
Junctional escape beat
High frequency QRS