heart muscle vs muscular tissue

heart muscle and muscular tissue both are nouns.

Word	Noun	Adjective	Verb	Adverb
heart muscle	Yes	No	No	No
muscular tissue	Yes	No	No	No

As nouns, muscular tissue is a hypernym of heart muscle; that is, muscular tissue is a word with a broader meaning than heart muscle:

heart muscle: the muscle tissue of the heart; adapted to continued rhythmic contraction
muscular tissue: animal tissue consisting predominantly of contractile cells

Other hypernyms of heart muscle include muscle.

heart muscle (noun)	muscular tissue (noun)
the muscle tissue of the heart; adapted to continued rhythmic contraction	animal tissue consisting predominantly of contractile cells