Abnormal heart rhythms Dr Trisha Macnair Not all abnormal heart rhythms (arrhythmias) are dangerous. In fact, an abnormal heartbeat is a common occurrence.

In this article

What causes them? What are the symptoms?

How are they diagnosed? What's the treatment?

Most people have an occasional extra heartbeat, usually without noticing it. Excessive stress, lack of sleep and stimulants, such as caffeine and nicotine, increase the risk of arrhythmias, as can medications, such as decongestants and alcohol.

Abnormal heart rhythms can also signal a major heart problem, such as an abnormality of the heart muscles, valves or electrical conducting system. They can be a sign that the heart has been damaged, for example, after a heart attack.

The rate at which the heart beats is important because it determines how much blood, oxygen and other vital nutrients are delivered around the body. If you run, for example, you need more oxygen and energy, so your heart rate must increase.

The heart has its own natural built-in pacemaker, called the sinoatrial node (or sinus node). Electrical impulses are triggered here and travel through a system of nerve wiring around the heart, so different parts of the heart beat in a regular order to make it function efficiently as a pump.

Faults with this wiring system are one of the main causes of abnormal heart rhythms.

If your heart rate is too fast (tachycardia), too slow (bradycardia) or very irregular, the heart won't work as an efficient pump and deliver all the blood your body needs.

Whatever the abnormal heart rhythm, common symptoms include:

• Feeling faint - an inefficient pump causes low blood pressure
• Palpitations - your heartbeat may feel fluttery or irregular, or you may detect a missed or skipped beat
• Shortness of breath and swollen ankles
• Chest pain - in extreme situations, the heart may beat so fast it interferes with the blood supply to the heart muscle and brain, and may result in a heart attack or brain damage

It's unlikely you'll be able to detect an abnormal heart rhythm yourself, although checking the rate and regularity of your pulse may give you a rough idea if there's a problem.

For an exact diagnosis, an electrocardiogram (ECG) is needed. Some abnormal heart rhythms are intermittent, so continuous heart monitoring, using special devices, may be needed to detect the problem.

Treatment of abnormal heart rhythms depends on the cause. An underlying disease, such as thyroid problems, may need to be treated.

A GP may suggest simple steps to rule out triggers, such as stress, but most people in the UK can expect to be assessed by a specialised cardiac unit, so the exact arrhythmia can be pinpointed.

A variety of drugs are used to control abnormal heart rhythms, while in some cases a pacemaker may need to be fitted.

Some of the most dangerous arrhythmias are those that affect the ventricles, the large muscular chambers of the heart. These can cause sudden death in someone who appeared previously fit and well.

Pacemakers are used to treat this sort of dangerous fast heart rhythm. They act by sensing the abnormal electrical stimuli in the heart and overriding them, sometimes by delivering a tiny electrical shock within the heart.

Occasionally, surgery is needed to cut abnormal nerve wiring or to destroy an area of heart tissue that's normally responsible for triggering abnormal electrical impulses.

This article was last medically reviewed by Dr Rob Hicks in November 2007