Abnormal heart rhythm or cardiac arrhythmia is most commonly caused by atrial fibrillation: atrial fibrillation involves the two larger, upper chambers of the heart and fibrillation is the medical term used to describe "quivering" of the affected muscles of the heart.

Before we take a more detailed look at atrial fibrillation, we must first understand a little about the structure of the heart to better understand what is happening with this condition and how we treat it.

The heart is composed of four chambers; as we have already said, the two larger chambers, known as atria, sit on top of two smaller chambers known as ventricles and each atrium is connected to the lower ventricle. The atrium's job is to take in blood after it has passed through the lungs and which is then rich in oxygen waiting to be delivered to the rest of the body. The atrium then contracts to force this blood into the lower ventricle. The ventricle is smaller than the atrium but much more powerful and when it contracts, this forces the blood out of the heart and around the body under pressure.

It is the double contraction of the atria followed by the ventricles which forms the typical heart beat we hear as a double thud - "duh-dum".

With a-fib, the regular double-beat becomes uncoordinated and this leads to blood not being transferred to the ventricles when it is supposed to - the blood literally misses the beat of the heart.

The actual cause is usually that the electrical signal which coordinates the heart is disrupted or not passing across the heart as it needs to in order to trigger the contraction of the muscles. Disruption is frequently caused by the electrical signal being drowned out by electrical impulses generated elsewhere by the atria or by the pulmonary system. This creates the arrhythmia or irregular heartbeat and an episode may last for a few moments or for an extended period of time, sometimes for years until it is detected.

Fortunately, a-fib is not usually life threatening but a range of symptoms may present themselves and are not generally pleasant - fainting, palpitations, pain in the chest or more seriously, congestive heart failure. Having atrial fibrillation will lead to a higher risk for other illnesses such as strokes due to blood clots forming from the blood which pools in the atrium due not being transferred fully to the ventricle. In general, those with atrial fibrillation are seven times more likely to suffer a stroke than the general population but other risk factors also need to be taken into account.

Treatment for atrial fibrillation includes medication used to slow or regulate the beat of the heart while a pace maker may be fitted to ensure the electrical signal used to regulate the contractions allows for coordinated contractions. Surgery may be performed to prevent atrial fib from recurring which may be minor (inserting a catheter) or major if the heart or electrical generation is significantly damaged. Those with atrial fib are frequently treated with anti-coagulants such as Warfarin to reduce the risk of blood clotting which causes strokes.



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