enlarged heart vs symptom

enlarged heart and symptom both are nouns.

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

As nouns, symptom is a hypernym of enlarged heart; that is, symptom is a word with a broader meaning than enlarged heart:

enlarged heart: an abnormal enlargement of the heart
symptom: (medicine) any sensation or change in bodily function that is experienced by a patient and is associated with a particular disease

enlarged heart (noun)	symptom (noun)
an abnormal enlargement of the heart	anything that accompanies X and is regarded as an indication of X's existence
	(medicine) any sensation or change in bodily function that is experienced by a patient and is associated with a particular disease