Atrial fibrillation is a heart rhythm disorder characterized by the atria ceasing to contract concertedly, which causes a chaotic heartbeat. In atrial fibrillation the rate of heart beats varies from 100 to 175 beats per minute. This pathologic condition is accompanied by a partial contraction of atrium which disturbs the normal process of transferring impulses to the heart ventricles. The insufficient contractions of ventricles inhibit the heart from ejecting blood in a normal mode.
Atrial fibrillation or AF, the most common type of arrhythmia, is a problem with the rate or rhythm of the heartbeat. During an arrhythmia, the heart can beat too fast, too slow, or with an irregular rhythm.
AF occurs if rapid, disorganized electrical signals cause the heart's two upper chambers—called the atria—to fibrillate. The term "fibrillate" means to contract very fast and irregularly.
In AF, blood pools in the atria. It isn't pumped completely into the heart's two lower chambers, called the ventricles. As a result, the heart's upper and lower chambers don't work together as they should.
This disorder is one of the most widespread amongst those arrhythmias that are significant for human health in cardiac patients. One in every 200 people suffers from the condition. Its prevalence rate in the adult population increases with age, with 3.5% of those between 50 and 60, and 9% of people in their 80-90’s. Also, sex influences the manifestation of this disease – women are 1.7 times less likely to suffer from atrial fibrillation than men.
During the process of fibrillation atria cannot be emptied properly, which in turn can provoke the stagnation of blood in the atria and may result in blood clotting. If a part of a blood clot breaks down and gets into the blood vessel, it may occlude an artery in any body part. Stroke takes place when a clot of blood occludes the cerebral artery.
In clinical practice, the terms used for atrial fibrillation relate to the pace and intensity of the cardiac contractions:
- Paroxysmal form – an arrhythmia which once appeared can be over within 7 days without any outside interference and is of attack-like nature. It may occur any number of times during the day and be over without any assistance, and between attacks a normal heart rhythm is observed;
- Persistent form – in this case arrhythmia cannot disappear without any interference. This form requires the use of cardioversion (restoration of the heart rate by means of medicines or using defibrillator discharge). Also, arrhythmia is considered to be of a persistent form if it lasts more than seven days;
- Permanent (chronic) form – this form is diagnosed if the normal heart rate takes turns with arrhythmia and lasts for an extended period (over a year) and the restoration of the rhythm cannot be maintained without assistance and remedial measures are not helpful.