EDP column by Professor Ketan Dhatariya
“I recently started having palpitations and felt my heart beating very fast. My doctors tells me I have AF. What is this?”
Atrial fibrillation – or AF -is uncoordinated electrical activity within the upper two chambers of the heart. Normally the heart beats slowly and regularly. These contractions originate from a specialised part of the heart called the sino-atrial node. The electrical signals pass along specialised heart tissue the trigger a coordinated contraction of the muscles of the upper two chambers – the atria. These chambers then squeeze and push blood into the lower two chambers of the heart – the ventricles. The electrical impulse that caused the atria to contract then passes into the ventricles through another ‘switch’ called the atrio-ventricular node. This impulse then causes the ventricles to contract. This causes blood to be pumped out of the heart and into the lungs and around the body. This whole process takes a fraction of a second, with the heart beating about 70 to 80 times per minute in adults.
The whole process is very dependent on the electrical activity within the heart to be regular. Occasionally things start to go wrong and the electrical impulse is not generated from within the specialist site, but from anywhere within the atria. This means that the electrical signal is not conducted along the normal pathway. This means that the muscles that are usually stimulated in a very precise order are set off in random. These electrical signals then go through the atrio-ventricular node at irregular times, leading to an irregular heart beat, and the perception of palpitations.
There are several causes for AF. These include ischaemic heart disease, where there is hardening of the blood vessels leading to a reduction in the oxygen supply to the heart muscle. The most common causes of this are smoking, poorly controlled diabetes, a family history of heart disease, and a raised cholesterol. Other causes of AF include high blood pressure, an over active thyroid gland, problems with the valves within the heart, lung disease and excessive alcohol. Occasionally no cause is found.
Treatments include ways of slowing the heart down, but also trying to re-establish a regular heart beat. This can be done using a variety of tablets, or occasionally by passing a small electric shock through the heart to ‘re-set the electrics’.
It is important to treat this condition because it can lead to problems. These include low blood pressure, or importantly, areas within the atria not contracting properly and the blood pooling. This can lead to clots within the heart. Often, it is necessary to take medication to thin the blood to stop this from happening.
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