antiarrhythmic medication

NOUN
25 LETTERS · STARTS WITH A

antiarrhythmic medication is a valid 25-letter word worth 42 points in Scrabble and 45 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
A1N1T1I1A1R1R1H4Y4T1H4M3I1C3M3E1D2I1C3A1T1I1O1N1
1 + 1 + 1 + 1 + 1 + 1 + 1 + 4 + 4 + 1 + 4 + 3 + 1 + 3 + 0 + 3 + 1 + 2 + 1 + 3 + 1 + 1 + 1 + 1 + 1 =42 PTS
DOUBLE WORD → 84TRIPLE WORD → 126
MEANING

What does antiarrhythmic medication mean?