SA node vs pacemaker

SA node and pacemaker both are nouns.

Word	Noun	Adjective	Verb	Adverb
SA node	Yes	No	No	No
pacemaker	Yes	No	No	No

As nouns, SA node and pacemaker are synonyms defined as:

SA node and pacemaker: a specialized bit of heart tissue that controls the heartbeat

Other synonyms of SA node include cardiac pacemaker, sinoatrial node.

SA node (noun)	pacemaker (noun)
a specialized bit of heart tissue that controls the heartbeat	a horse used to set the pace in racing
	an implanted electronic device that takes over the function of the natural cardiac pacemaker
	a specialized bit of heart tissue that controls the heartbeat
	a leading instance in its field