Normally the AV Node acts as the ‘gate-keeper’ and all electrical signals from atria must pass through the AV Node before travelling down the Left and Right Bundle Branches to activate the Ventricles.
Some patients are born with an extra electrical fibre that connects the atria and the ventricles. These are called Accessory Pathways and provide an extra electrical connection from the Atria to the Ventricles bypassing the AV Node.
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