Hi
Thanks for writing to the forum!
A pain radiating to left arm definitely warrants a 12 lead EKG—this could be a heart attack.
However there are other things that also need to be investigated. Shoulder joint problems can cause a pinched nerve and pain along the arm. Compression of cervical nerves due to vertebral canal stenosis, slipped disc, degerative disease, spondylosis, tumor, bone disease etc is another possibility.
I think you should discuss these possibilities with your doctor. It is difficult to comment beyond this without examining. A comprehensive investigation is required keeping all the points in mind. Please let me know if there is any thing else and do keep me posted. Take care!
It could be tendonitis, bursitis, or it serious as a heart attack, especially if you are also having any other symptoms, such as shortness of breath and sweating at the same time you get these pains. I'd go in and get it checked.