How does this condition work?

How does this condition work?

Your heart has four chambers. The lower chambers are the left and right ventricles. The upper chambers are the left atrium and right atrium (when you refer to both of them, the plural term is atria). Atrial tachycardia affects only the atria, causing them to beat too quickly.

Under normal conditions, each heartbeat starts with an electrical pulse that starts in a cluster of specialized cells. This is the sinoatrial (SA) node, the heart’s natural pacemaker, and it’s located in the right atrium. Next, electricity flows from the SA node to the rest of your heart. This cascade effect causes heart muscle cells to squeeze as the cascade passes through them.

Atrial tachycardia happens when the upper chambers of your heart squeeze faster than the lower chambers. A faulty electrical signal can cause this, or it might happen because the cells are malfunctioning. There are three ways that this usually happens.


While the SA node is your heart’s main pacemaker, there are backup pacemakers in your atria. These cells can take over and keep your heart beating if your SA node stops working, an ability called automaticity. When the SA node is working properly, it’s supposed to prevent automaticity from happening in these other backup pacemakers. When a backup pacemaker ignores that suppression and acts on its own, this is called enhanced automaticity. It can also happen when the SA node activates at the wrong time.

Heart muscle generates and conducts electricity by using chemical elements like sodium, potassium and calcium to create positive and negative charges. That’s how heart muscle cells can naturally react to an electrical pulse, but only if the pulse is strong enough. When the balance of the chemical elements isn’t right, the cells can react to a lower-than-normal electrical charge. This is called abnormal automaticity.

Atrial tachycardia caused by automaticity is more common in younger individuals.

Triggered activity

Sometimes, the cells may react to a pulse and then act again after the pulse has passed. This is called triggered activity. It can sometimes happen because of a chemical imbalance in the heart muscle cells. While this is similar to abnormal automaticity, there’s a key difference: The incorrect reaction has to follow a correct reaction to an electrical signal.


Reentry happens when an electrical signal that tells the heart muscle to beat gets redirected and forms a circuit by crossing through the same cells more than once. The SA node can sometimes be part of this circuit (though this is rare). It can also happen with faulty activity from enhanced automaticity, as mentioned above. Reentry can happen in a very small area (micro-reentry), or it can happen over wider areas of the heart (macro-reentry).

Atrial tachycardia caused by micro-reentry is more common in older individuals.

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