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Galway Cardiology

Hearts Electrical System

Electrical System of the Heart.

Normally with each heartbeat, the electrical impulse begins at the sinoatrial (SA or sinus) node in the right atrium. The sinus node produces the electrical impulses that set the rate and rhythm of the heart beat. The electrical activity spreads through the walls of the atria and causes them to contract. The electrical impulse then crosses the AV node and spreads down to the ventricles, causing them to contract. This generates the heart beat.  

With atrial fibrillation

The SA node does not direct the heart’s electrical rhythm. Instead, many different impulses rapidly fire causing a very fast, chaotic rhythm in the atria. Because the electrical impulses are so fast and chaotic, the atria cannot contract and/or squeeze blood effectively into the ventricle. These electrical impulses originate in the pulmonary veins from pacemaker like cells, similar to those present in the heart’s normal pacemaker or sinus node. Atrial fibrillation can start at any age but most commonly starts in the fifties and sixties. It is a lifelong condition if not treated effectively. Initially symptoms are brief and intermittent. Over time they become more frequent and prolonged in duration. Eventually the person develops permanent atrial fibrillation being out of rhythm all the time. It is possible to cure atrial fibrillation if treated in the early stages when symptoms are still brief and intermittent. This is because scar tissue develops in the left atrium over time and maintains the arrhythmia.
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Tel: +353 (0) 91720170                         brendan.ocochlain@galwayclinic.com
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