cardiac arrhythmia vs arrhythmia

cardiac arrhythmia and arrhythmia both are nouns.

Word	Noun	Adjective	Verb	Adverb
cardiac arrhythmia	Yes	No	No	No
arrhythmia	Yes	No	No	No

As nouns, cardiac arrhythmia and arrhythmia are synonyms defined as:

cardiac arrhythmia and arrhythmia: an abnormal rate of muscle contractions in the heart

cardiac arrhythmia (noun)	arrhythmia (noun)
an abnormal rate of muscle contractions in the heart	an abnormal rate of muscle contractions in the heart