When my husband had the heart attack the pain was excruciating but everybody, doctors included thought he had thrown his shoulder out again. He had done that in the past. If it were not for one ER doc that insisted that he be admitted for serial bloodwork he would have been sent home to see an ortho. In retrospect it was pretty scary. He ended up having a quadruple bypass4 days later.
Glad your pain passed Jerry.
Ouch, I just had a problem with a sharp pain in my left shoulder, not under the arm. I didn't even think it might be heart related. As it turns out I had my annual physical and my primary care does a EKG as part of it. We talked about the shoulder paint and prescribed an X-ray. That done, nothing was found, again no thought of my heart. As it worked out the pain as passed, not there the last few days.
Not trying to scare you but when my husband had a heart attack his pain was under his arm and in his shoulder. You need to get it checked.
Sounds like a good time to get a check-up, one that includes an EKG and discussion about you symptom.