cardiomegaly vs megalocardia

cardiomegaly and megalocardia both are nouns.

Word	Noun	Adjective	Verb	Adverb
cardiomegaly	Yes	No	No	No
megalocardia	Yes	No	No	No

As nouns, cardiomegaly and megalocardia are synonyms defined as:

Other synonyms of cardiomegaly include enlarged heart, megacardia.

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