blink of an eye vs heartbeat

blink of an eye and heartbeat both are nouns.

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

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

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

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

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