cardiologist vs heart specialist

cardiologist and heart specialist both are nouns.

Word	Noun	Adjective	Verb	Adverb
cardiologist	Yes	No	No	No
heart specialist	Yes	No	No	No

As nouns, cardiologist and heart specialist are synonyms defined as:

cardiologist and heart specialist: a specialist in cardiology; a specialist in the structure and function and disorders of the heart

Other synonyms of cardiologist include heart surgeon.

cardiologist (noun)	heart specialist (noun)
a specialist in cardiology; a specialist in the structure and function and disorders of the heart	a specialist in cardiology; a specialist in the structure and function and disorders of the heart