Left Arm Numb Fast Heartbeat Sudden Intense Pounding Heartbeat, Numbness Left Side?

Sudden intense pounding heartbeat, numbness left side? - left arm numb fast heartbeat

My daughter is 12 years. Over the past three weeks 4 episodes that I saw where you suddenly sense that the kind of cramp in his left arm, shoulder, and had then left to sleep (with the feeling, excluding the face) and his heart beat so hard It seems that it is having convulsions. She says it's hard to breathe when it happens, but no pain. Then, after about 20 seconds, she vanishes as suddenly as it appeared, and continue as if nothing had happened. When he arrived this morning I had his heart in his neck and did not beat him super fast, but only a little faster than normal. I took him to the doctor tomorrow, but I wanted to see if anyone has any information. or ideas of what it could be.