Common complaints: Palpitations

WHEN SOMEONE says 'my heart was in my mouth' they mean they were aware of the heartbeat, which was rapid and forceful. A fast, strong heartbeat is normal during excitement and after exertion, but if the heart's action becomes obvious in bed at night or at rest during the day there is something wrong.

A forceful, regular heartbeat may be due simply to anxiety - and worrying about it may make the anxiety worse. A fast heart rate may be a symptom of a hormonal disturbance such as overactivity of the thyroid gland. The heart may have to work harder than usual if the blood is too thin (anaemia), or if one or more of the heart valves is faulty, or if there is an abnormal connection between the two sides of the heart due to a birth defect.

A very rapid heartbeat - two or three times the normal rate - is termed tachycardia and typically occurs in attacks lasting a few minutes but sometimes longer. During an attack there is not only the sensation of a fast heart rate but also a feeling of faintness (because the heart's pumping action is less efficient at very high speeds). The diagnosis of the precise type of tachycardia usually requires an electrocardiogram or ECG - an electrical recording of the heart's action. With each beat, changes in voltage occur in the heart chambers, and these electrical fluctuations may be detected and recorded by electrodes fixed to the arms, legs and chest. If the attacks are brief and intermittent, then a continuous recording of the ECG may be made for 24 hours on a tape machine worn on a belt. Once the type of tachycardia has been identified, treatment may be given. If attacks occur only rarely and are not associated with any serious heart disease, the victim may be taught one or more ways of stimulating the vagus nerve, which slows the heart. These include massaging the carotid artery in the neck, immersing the face briefly in cold water, and applying pressure to the eyeball (though this carries a risk of damaging the eye). Persistent attacks usually have an identifiable cause such as thyroid disease or damage to the heart's electrical control system from narrowing of the coronary arteries. If the underlying cause cannot be reversed, treatment with drugs will usually control the palpitations.

Irregularity of the heart due to extra beats is usually harmless, but as with tachycardia, a precise diagnosis requires an ECG recording. The irregularity may be due to atrial fibrillation, in which the smaller heart chambers beat ineffectually. Treatment will usually be given to restore the rhythm to normal and so improve the efficiency of the heartbeat. In young people, however, the most common irregularity is the occurrence of occasional extra beats known as extra systoles. There is typically an unusually powerful beat which is often followed by a long pause in which the victim may feel that the heart has stopped. It is often the pause rather than the extra beat that causes the discomfort. Extra systoles do not usually indicate any form of heart disease. Among the possible causes are heavy smoking, too much coffee or too much alcohol.