Atrial Fibrillation

The most common heart rhythm disturbance

BACKGROUND

The heart is a pump responsible for maintaining blood supply to the body. It has four chambers. The two upper chambers (the right atrium and left atrium) are the chambers that receive blood as it returns from the body via the veins. The lower chambers (the right and left ventricle) are the chambers responsible for pumping the blood out to the body via the arteries. Like any pump, the heart has an electrical system that controls how it functions.

Normal heart rhythm. (The Electrical System)

In order for the heart to do its work (pumping blood throughout the body), it needs a sort of spark plug or electrical impulse to generate a heartbeat. Normally this electrical impulse begins in the upper right chamber of the heart (in the right atrium) in a place called the sino-atrial (SA) node. The SA node is the natural pacemaker of the heart. It provides the electrical spark that drives the heart to beat approximately 60 to 100 times per minute. If you are exercising, doing strenuous work or you are under a lot of stress, your heart rate may be faster. When you rest or sleep your heart rate will slow down. Certain medications may also slow the heart rate. All of this is appropriate.

From the SA node, the electrical impulse travels along the heart’s conduction system (the electrical wiring of the heart). The impulse spreads over the right atrium and reaches the Atrio-ventricular (AV) node. This is a very important structure in the heart because it is the only electrical connection between the top chambers and the bottom chambers. It is therefore the only way in which an electrical impulse can reach the pumping chambers (the ventricles). The impulse spreads through the AV node and down into the lower chambers or ventricles of the heart. This causes them to contract and pump blood to the lungs and body.

SYMPTOMS

 

How does atrial fibrillation occur?

In some hearts, an abnormal heart rhythm develops when an electrical impulse either starts from a different location other than the SA node, or follows a route (or pathway) that is not normally present. This is what happens in atrial fibrillation. An abnormal electrical focus Multiple electrical short circuits develop in the upper heart chambers as shown in the diagram below.

Atrial Fibrillation is due to multiple short circuits in the upper chambers of your heart termed the left and right atria.

Consequences of Atrial Fibrillation

These rapid short circuits have several consequences:

  1. The short circuits are conducted down into the pumping chambers via the AV Node and drive these chambers very rapidly and irregularly. This produces palpitations, shortness of breath, and tiredness. In some people it can also cause dizzyness and chest pain. Episodes of atrial fibrillation can come and go in some people and in others atrial fibrillation is present permanently.
  1. The short circuits result in ineffective pumping of the upper chambers. This leads to slow blood flow in both of these upper chambers (the left and right atria). This can rarely cause blood clots and possibly stroke. The reason you are taking aspirin or warfarin is in order to thin the blood and prevent stroke.

 

What causes atrial fibrillation?

There are many heart conditions that can lead to atrial fibrillation. These include previous heart attack, heart valve problems, high blood pressure and many others. However, in many people, atrial fibrillation occurs when the heart appears otherwise healthy and the reason is unknown. In these people certain things can act as a trigger to an episode. These include caffeine, alcohol, stress, tiredness and vigorous exercise amongst others. However, in many people, episodes of atrial fibrillation occur “out of the blue” with no particular trigger


results of testing heart conditions

TREATMENT

What treatments are available for atrial fibrillation?

  1. This is the usual way of treating atrial fibrillation. In many people medication are highly effective. However, medications do not cure the condition. They simply make episodes less frequent and less severe. In some people however, the medications are less effective. Medication may also produce side effects.
  2. DC Shock. When the heart is in fibrillation it can be reverted to the normal rhythm with a “shock on the chest”. You receive a short general anaesthetic and the shock reverts the rhythm to normal in the majority of cases. With this approach the possibility of the fibrillation returning remains present. Therefore most patients will also require a medicine to try to prevent the fibrillation coming back.
  3. Blood thinning medication. Because of the risk that atrial fibrillation may cause blood clots in the heart most patients with this heart rhythm disturbance will require blood-thinning medication to prevent blood clots forming. At your doctors discretion this may either be with aspirin or warfarin or one of the newer agents (NOACS)
  4. For some patients with atrial fibrillation when symptoms are severe and medications have been unsuccessful, a permanent pacemaker may be implanted. By itself the pacemaker will not improve the way you feel. However, following this a special procedure called AV node ablation (sometimes also called His bundle ablation) can be performed. This procedure is a simple procedure which effectively “knocks out” the AV node. This will prevent any of the electrical short-circuits in the atria from reaching the ventricles. The pacemaker will now have complete control of your heart rhythm. The heart rhythm will be regular and will no longer race rapidly. The procedure is not a cure but does effectively control the symptoms.

 

Can Atrial Fibrillation Be Cured?

At the present time only very few patients with atrial fibrillation can be cured with a procedure termed radiofrequency ablation. Unfortunately, for the majority of patients with atrial fibrillation this is not possible at the present time. If you have a type of atrial fibrillation that may be suitable for this procedure, it will be discussed with you.

Atrial fibrillation is a very common condition and is the focus of much research. It is possible that in the future, our ability to cure this condition will improve.

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