An atrial flutter is arrhythmia, or abnormal rhythm, of the atria of the heart. The atria are the two upper chambers of the human heart. Flutters occur most commonly in people with cardiovascular problems, but they can also affect healthy people. It is usually short-lived, either going away, or degenerating into atrial fibrillation, another form of arrhythmia that is usually chronic. There are two types of atrial flutter, Type I and Type II; the latter is rarer, and causes faster arrhythmia.
Atrial flutter is characterized by palpitations, or an abnormal awareness of the heart's beating, along with tachycardia, or an abnormally fast heartbeat. It is not necessarily something to worry about and may, for example, simply be a sign of mild overexertion that resolves itself within a few minutes of decreasing strenuous activity. If the condition persists, however, especially in a person with any kind of cardiovascular illness or weakness, it may also be accompanied by dizziness, shortness of breath, chest pains, and nausea.
In extreme cases, atrial flutter can lead to chronic breathlessness and even heart failure. It can also cause blood to pool in the atria and eventually form a blood clot in the heart. If the blood clot travels to the brain, stroke can result.
A reentrant rhythm in the right or left atrium causes atrial flutter. When the heart is functioning normally, a heartbeat will involve electrical impulses passing through each cell of the atrium only once. During the flutter, some cells are slow to respond to the impulse. This causes the initial impulse to be misinterpreted, when the slow cells finally respond, resulting in a continued loop of electrical activity.
The resulting heartbeat will not be as fast as the impulses in the atria, since heartbeat is measured by the contractions of the ventricles, the lower two chambers of the heart; however, it will be faster than normal. The atria transmit an electrical impulse to the ventricles via the atrio-ventricular node, which is able to slow down excessively fast impulses coming from the atria. When the atrio-ventricular node slows the impulse in this manner, heart block occurs, resulting in the symptoms that characterize atrial flutter.
This condition may be treated with medication to prevent the formation of blood clots and to control the heart's rate or rhythm. Cardioversion, the application of a low current electrical energy to the heart, can also help return the heartbeat to normal. Ablation, in which a scar is surgically created to destroy the circuit in the heart causing atrial flutter, is another option.