heart failure vs heart disease

heart failure and heart disease both are nouns.

Word	Noun	Adjective	Verb	Adverb
heart failure	Yes	No	No	No
heart disease	Yes	No	No	No

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

heart failure: inability of the heart to pump enough blood to sustain normal bodily functions
heart disease: a disease of the heart

Other hypernyms of heart failure include failure, cardiopathy.

heart failure (noun)	heart disease (noun)
inability of the heart to pump enough blood to sustain normal bodily functions	a disease of the heart