heartbeat vs diastole

heartbeat and diastole both are nouns.

Word	Noun	Adjective	Verb	Adverb
heartbeat	Yes	No	No	No
diastole	Yes	No	No	No

As nouns, diastole is a hyponym of heartbeat; that is, diastole is a word with a more specific, narrower meaning than heartbeat:

heartbeat: the rhythmic contraction and expansion of the arteries with each beat of the heart
diastole: the widening of the chambers of the heart between two contractions when the chambers fill with blood

Other hyponyms of heartbeat include systole, pounding, throb, throbbing.

heartbeat (noun)	diastole (noun)
an animating or vital unifying force	the widening of the chambers of the heart between two contractions when the chambers fill with blood
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)