cardiomyopathy vs heart disease

cardiomyopathy and heart disease both are nouns.

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

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

cardiomyopathy: a disorder (usually of unknown origin) of the heart muscle (myocardium)
heart disease: a disease of the heart

Other hypernyms of cardiomyopathy include cardiopathy.

cardiomyopathy (noun)	heart disease (noun)
a disorder (usually of unknown origin) of the heart muscle (myocardium)	a disease of the heart