Yes, shoulder pain may be a sign of heart attack as there is a relationship between shoulder pain and heart attack as follow::
The heart attack can cause pain in the chest or shoulder, if you suffer from pain in the chest or shoulder, or feeling pain in the left side arm, this may be a sign of having a heart attack, but the heart attack is not the only reason for this Kinds of pain, it may be accompanied by some symptoms, burning, pressure and pain, and sharp pain during coughing or sneezing, and the pain may increase over a period of minutes, but the pain may be concentrated in one area, and it may extend to the back, jaw, neck and left arm, and the pain may last A very short period, but if the symptoms are accompanied by sudden nausea, cold sweats and trouble breathing, these symptoms may last for days or hours