Tachycardia presents as an abnormally rapid heart rate (especially rates above 100 beats per minute in an adult). Symptoms of tachycardia include a pounding in the chest, breathlessness, upset stomach, dizziness, weakness, feeling faint and loss of consciousness. It may last from several minutes to a few days. Tachycardia can be induced by medical conditions, pregnancy, fever, heavy exercise or extreme anxiety.
While a rapid heart rate is not generally life threatening, it can make the sufferer anxious or frightened.
Taking deep breaths and holding one's breath are two simple ways to gently slow down a rapid heart rate (naturally, breath held for too long will result in further dizziness or faint feelings). Other methods of slowing the heart include having a long slow drink of water or splashing the face with cold water.