Cardioversion is the term given to any process that restores an abnormal heart rhythm to a normal one. Though there are a variety of abnormal heart rhythms, the most common abnormal heart rhythm to benefit from cardioversion is atrial fibrillation, known simply as "AF."

In atrial fibrillation, the heart's upper chambers quiver rapidly - or "fibrillate" - at rates of approximately 400/minute. This chaotic electrical rhythm, although confined to the heart's upper chambers, the atria, usually has an adverse impact on the lower chambers, the ventricles, resulting in a fast and irregular pulse. Though some patients have no symptoms whatsoever from their atrial fibrillation, others may complain of palpitations, breathlessness or fatigue.

Different forms of cardioversion exist, the most common being electrical cardioversion - often referred to as "DC" or direct-current cardioversion - which involves delivering a specialised form of medically-safe shock to the heart either through the chest wall or within the heart via a small temporary wire passed through a vein to the heart. In other instances, cardioversion may take the form of medication, given either by injection or by mouth, with the intention being to restore the heart's rhythm to normal over a period of time, be it several minutes, hours or days.

In the case of electrical cardioversion to treat atrial fibrillation, the procedure is usually performed as a day-case procedure in a hospital environment after having nothing to eat for 6 hours prior. Short-acting intravenous sedatives or a brief general anaesthetic are administered to prevent any discomfort prior to delivering the electrical shock.

Patients usually wake up quickly after the procedure and are allowed home later on the same day after a brief period of observation, during what is usually a short recovery period.

It is common to experience minor skin irritation and a muscular ache for a couple of days following the cardioversion procedure, if it is performed through the chest wall. If, on the other hand, your cardioversion procedure is performed using a wire within the heart, there may be minor bruising at the site where the wire entered the vein (eg, arm, neck or leg) but usually no skin irritation or muscular aching will occur.

It is important not to drive or make important decisions for approximately 24 hours after an electrical cardioversion procedure so as to allow time for the sedation to fully wear off.

Though it is usually possible with electrical cardioversion to restore the heart's normal rhythm in approximately 90% of patients at the time of their procedure, unfortunately only half of these patients will maintain their normal rhythm over the subsequent year. Should atrial fibrillation recur, further cardioversion procedures may be worthwhile, with or without the use of additional heart rate or rhythm medication beforehand. Your doctor will usually be able to give you tailored advice if you happen to experience recurrent atrial fibrillation after an initially successful cardioversion procedure.

Prior to any cardioversion procedure for atrial fibrillation, it will be necessary for the doctor or nurse looking after you to ensure that your risk of blood clot formation - which may occur as a consequence of the less efficient cardiac contractions that result from atrial fibrillation - is as low as it can be. This is done by ensuring that your blood has been kept sufficiently thin by the effective use of a drug called Warfarin in the 3-4 weeks immediately preceding your cardioversion procedure.

Occasionally, if your atrial fibrillation has been present for less than 48 hours, your doctor may recommend that a specialised ultrasound study of the heart - known as a transoesophageal echocardiogram, or "T.O.E." - be performed in order to establish if it is safe for you to proceed with cardioversion, without resorting to the prior use of Warfarin.


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