Normally the heart beats at a rate of between 50 and 100 beats a minute, depending on what we are doing. We all experience variations in heart rhythm as we go about our everyday lives, our heart beats faster, for example, when we exercise, if we are excited or under stress, and slows down when we are relaxed or sleeping.
Sometimes we become aware of our heart beating – especially if it seems to be going too fast. This is known as palpitation and is usually quite harmless. Palpitations are often brought on by feeling nervous or angry, by exercise, a raised temperature, a stomach upset, alcohol or even over-the-counter cold cures. However, if you have had a heart attack these normal palpitations may cause great anxiety because you may fear you are having another heart attack.
People with coronary heart disease, atherosclerosis, high blood pressure and other changes in the blood vessels are prone to more marked variations in rhythm (called arrhythmias). This is because scarring or abnormal tissue deposits may disturb the electrical signaling system within the heart’s own pacemaker, the sinoatrial node. This may cause the heart’s cells to fire abnormally or create patches of electrically inert tissue, which in turn can cause the heart to beat abnormally fast (the medical term I tachycardia) or abnormally slowly (bradycardia).
We have already seen that a heart attack may set the ventricles beating fast and irregularly (ventricular fibrillation) .Another important and common type of tachycardia is known as atrial fibrillation. In this type of arrhythmia the atria (the upper chambers of the heart) beat extremely rapidly – the rate can reach 400 beats a minute. The AV node, which sends impulses from the atria to the ventricles, cannot cope with this and therefore sends only a selection of the impulses to the ventricles. As a result the ventricles beat quickly (say 180 beats a minute) and irregularly .Although the palpitations of atrial fibrillation can feel very unpleasant they are not immediately dangerous.
Fortunately most palpitations are a nuisance rather than life-threatening and many can be cured by avoiding trigger factors such as alcohol or over-the-counter cold remedies. More serious arrhythmias may need to be treated with special drugs. Alternatively, the doctor may suggest implanting a pacemaker or another procedure to regularize the heart’s rhythm.
