enlarged heart vs cardiomegaly

enlarged heart and cardiomegaly both are nouns.

Word	Noun	Adjective	Verb	Adverb
enlarged heart	Yes	No	No	No
cardiomegaly	Yes	No	No	No

As nouns, enlarged heart and cardiomegaly are synonyms defined as:

Other synonyms of enlarged heart include megacardia, megalocardia.

enlarged heart (noun)	cardiomegaly (noun)
an abnormal enlargement of the heart	an abnormal enlargement of the heart