What is Atrial Fibrillation?
The heart is a muscle divided into four chambers: two atria at the top, and two ventricles at the bottom. Electrical impulses from the sino-atrial node in the right atrium cause the sequential contraction of atria then ventricles in order to squeeze blood through the heart and out to the body. This is known as sinus rhythm.
In Atrial Fibrillation (AF), faulty signals are generated from other areas in the heart, causing rapid, inefficient 'quivering' contractions of the atria at a rate of 300-600 beats per minute. These fibrillating contractions do not cause the ventricles to contract at the same rate, but the ventricles do pick up on more impulses than normal, causing an increased rate of contraction in order to try to pump blood to the body. This leads to a high heart rate – sometimes up to 180-200 beats per minute. A rate this high leads to inefficient emptying of the blood through the heart, causing it to pool in the chambers and increasing the risk of stroke. With a lower volume of blood circulating around the body, patients can feel lethargic, breathless and dizzy.
Signs and Symptoms
Atrial Fibrillation can be acute and life-threatening, paroxysmal (intermittent), or chronic, and its symptoms can range in severity from mild lethargy to stroke. Recent studies in the US have estimated a rate of 70,000 strokes per year as a result of AF. There are no known causes for Atrial Fibrillation, but incidence tends to increase with age, and affects more men than women. Symptoms can often go unnoticed, and some patients are only diagnosed with Atrial Fibrillation when under investigation for some other medical reason; conversely, some patients are acutely aware of changes in their heart rhythm.
Symptoms can include:
- Rapid, weak pulse
- Shortness of breath
- Feeling of an uncomfortable, 'flopping' heartbeat (this results from
- Chest pain
Treatment focuses on two main areas:
Restoring normal rhythm either by using particular drugs, or through a process called cardioversion, where an electrical impulse is shocked through the heart in order to override the fibrillation of the atria and restore normal rhythm.
Reduction and control of rate by use of specific medications such as digoxin, beta blockers and calcium antagonists.
If these methods do not work, doctors may consider inserting a mechanical pacemaker to regulate rhythm.