There is no such thing as a minor heart attack
. Either you do or you don't have one. The doctor can take a blood sample and see by the enzymes if he had one or not.
The pain could have been anything from a tendinitis
in the arm, shoulder, neck to a bursitis
in the shoulder. It's becoming quite apparent that everyone now days that has a sore arm is having a heart attack, it can be easily proven with an enzyme check.
He should see a doctor to clear this up just in case he has heart problems and they're stating to raise their heads. Then he can be treated.