Atrial fibrillation: Atrial fibrillation (AF) is an irregular fast rhythm originating from the upper chambers of the heart (atria). Due to the very fast rate of the order of 400-600/minute, the upper chambers cannot contract properly and rather stand still in AF. Hence there is a risk of clot formation in the upper chambers. These clots can migrate to other parts of the body through the bloodstream and obstruct important blood vessels, causing diseases like stroke (with paralysis of parts of the body).
What causes atrial fibrillation?
There are causes which can cause transient AF and those which can cause it for a long time. A binge of alcohol intake can cause AF, which is usually self limited (holiday heart syndrome). Transient episodes can occur after a surgical procedure, often due to increased activity of the sympathetic nervous system (perioperative atrial fibrillation).
As age advances, the muscles in the upper chambers of the heart (atria) suffer progressive electrical changes. Hence the risk of the abnormal heart rhythm increases as age advances and is quite common in the very elderly.
Any disease which can cause enlargement of the upper chambers of the heart (atria) can cause AF. This can occur when the pumping function of the heart is reduced (heart failure). Obstruction or leakage of the mitral valve (between left upper and lower chambers of the heart) causes enlargement of left atrium. This can lead to AF.
What are the symptoms of atrial fibrillation?
When AF occurs suddenly it is felt as a rapid irregular beating of the heart. But if it occurs gradually, with a slow heart rate, it may not produce any symptom and it may be detected on routine check up with ECG. As AF often increases the heart rate, it can worsen the symptoms due to any preexisting heart disease and produce breathlessness, chest pain or giddiness.
How can atrial fibrillation be treated?
Atrial fibrillation can be treated with medications which can decrease the heart rate as well as those which correct the abnormal rhythm. If the cause is reversible, it can be addressed. Electrical treatment modalities like direct current shock for initial termination and catheter ablation for prevention of recurrence can also be considered. In catheter ablation, small electrodes are introduced into the heart to identify the location of electrical abnormality (mapping) followed by application of radio frequency energy to produce tiny burns (ablation). Cooling to sub zero temperatures with cryo probes is another method of ablation.
Why do persons with atrial fibrillation need medications to prevent the formation of blood clots?
Many patients with AF have a high risk of clot formation in the atria (upper chambers of the heart) due to local stasis of blood. This is because atria cannot contract effectively in AF. Clots can move out of the upper chambers and move into other blood vessels of the body blocking circulation to a region. This can cause various diseases like stroke (due to blockage of blood vessel of the brain). In order to prevent this adverse outcome, persons with AF need medications which reduce the chance of clot formation. But these medications have to be taken under close medical supervision with proper monitoring of clotting function. Otherwise they can cause harm due to bleeding, which can even be catastrophic.