heartbeat vs blink of an eye

heartbeat and blink of an eye both are nouns.

Word	Noun	Adjective	Verb	Adverb
heartbeat	Yes	No	No	No
blink of an eye	Yes	No	No	No

As nouns, heartbeat and blink of an eye are synonyms defined as:

heartbeat and blink of an eye: a very short time (as the time it takes the eye to blink or the heart to beat)

Other synonyms of heartbeat include flash, instant, jiffy, New York minute, split second, trice, twinkling, wink.

heartbeat (noun)	blink of an eye (noun)
an animating or vital unifying force	a very short time (as the time it takes the eye to blink or the heart to beat)
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)