PALPITATIONS

A palpitation is an awareness of the beating of the heart, whether it is too slow, too fast, irregular, or at its normal frequency. Palpitations may be brought on by overexertion, adrenaline, alcohol, disease (such as hyperthyroidism) or drugs, or as a symptom of panic disorder.

Nearly everyone experiences an occasional awareness of their heart beating but, when it occurs frequently, it can indicate a problem. Palpitations may be associated with heart problems, including valve abnormalities, but also with anaemia and thyroid dysfunction.

Attacks can last for a few seconds or hours, and vary in their frequency. Palpitations associated with other symptoms, including sweating, faintness, chest pain, dizziness or blackouts, indicate irregular or poor heart function and should be investigated by your doctor.

Source: wikipedia GFDL