heart surgeon vs cardiologist

heart surgeon and cardiologist both are nouns.

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

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

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

Other synonyms of heart surgeon include heart specialist.

heart surgeon (noun)	cardiologist (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