heartbeat vs periodic event

heartbeat and periodic event both are nouns.

Word	Noun	Adjective	Verb	Adverb
heartbeat	Yes	No	No	No
periodic event	Yes	No	No	No

As nouns, periodic event is a hypernym of heartbeat; that is, periodic event is a word with a broader meaning than heartbeat:

heartbeat: the rhythmic contraction and expansion of the arteries with each beat of the heart
periodic event: an event that recurs at intervals

Other hypernyms of heartbeat include recurrent event.

heartbeat (noun)	periodic event (noun)
an animating or vital unifying force	an event that recurs at intervals
the rhythmic contraction and expansion of the arteries with each beat of the heart
a very short time (as the time it takes the eye to blink or the heart to beat)