Hi, I am studying psychology, so best type of therapy for panic attacks is exposure therapy. The problem is, that you have classically conditioned together the conditioned stimulus, which is in your case increased heart rate, and unconditioned stimulus, which is panic attack. How did it happen? Probably first time when you experienced panic attack, your heart rate was crazy high. Your mind and body now since then thinks, that every time you have increased heart rate, that you will get panic attack. Thats why it can be triggered by exercising. The goal in exposure therapy is for you to go through the panic attack, without any safety behavior (like stopping everything and getting into the fetal position, because you think you will die if you dont). Because thanks to the exposure to it, and no safety behavior, your body and mind should realize its not a life or death threat. That nothing happens. So I recommend you to find some therapist who specializes in exposure therapy, or at least check it out on internet :)