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Cardiology Teaching Package

A Beginners Guide to Normal Heart Function, Sinus Rhythm & Common Cardiac Arrhythmias

Atrial Fibrillation

AF is the most common arrhythmia in most countries and is easily managed with the correct treatment. In Atrial Fibrillation there is a complete absence of a Sino-Atrial stimulus which would result in a P wave.

The role of the SA node stimulus is to depolarise the cells and cause a wave of contraction throughout the Atria. When the valves open between the atria and ventricles, up to 70% of blood within the atria falls through into the ventricles with the aid of gravity. However, the final 30% of blood remaining within the atria requires the contaction of the atria in order to progress into the ventricles. This is known as the "atrial kick".

In AF the atria are fibrillating, or quivering, and the atrial kick does not occur, with the result that the arterial and coronary circulations lose at least 30% of their normal supply.

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