As u said u get pain in left arm when palpitations, it is possible that one can have chest pain
along with left arm pain
or only left arm pain during palpitation when the rate is too high. Have u got checked that what kind of palpitation u r having.tablet inderal
is good for fast palpitation, it may cause stomach upset
as u did not mentioned about duration of treatment that how long u r on medicine. With inderal u can have stomach upset for some time like a month on two. It usually settle down its own. I advice u to take medicine after food and be in upright position after lunch or dinner then look for symptoms.