People often fear the worst when they're having an anxiety attack. Most of the time, there’s no underlying physical problem, such as a real heart attack. But you should get the medical all clear if you have repeat anxiety attacks, just to be sure you don’t need additional treatment. Then find a cognitive behavioral therapist with experience treating anxiety to help you through.
People with panic disorder often worry about when the next attack will happen and actively try to prevent future attacks by avoiding places, situations, or behaviors they associate with panic attacks. Worry about panic attacks, and the effort spent trying to avoid attacks, cause significant problems in various areas of the person’s life, including the development of agoraphobia (see below).