A palpitation is an abnormality of heartbeat that causes a conscious awareness of its beating, whether it is too slow, too fast, irregular, or at its normal frequency. The word may also refer to this sensation itself. It can be caused by (but should not be confused with) ectopic beat, which is a more specific diagnosis. The difference between an abnormal awareness and a normal awareness is that the former interrupts other thoughts, whereas the latter is almost always caused by a concentration on the beating of one's heart. Palpitations may be brought on by overexertion, adrenaline, alcohol, nicotine, caffeine, cocaine, amphetamines, and other drugs, disease or as a symptom of panic disorder...