Panic attacks typically involve an abrupt onset of intense physical symptoms — rapid heartbeat, shortness of breath, sweating, trembling, chest tightness, nausea, dizziness, and a strong sense of danger or dread. Many people who experience them for the first time worry they are having a heart attack or a medical emergency. If you have had unexplained episodes of intense physical distress accompanied by fear, it is worth discussing with both your doctor and a mental health professional.