Atrial flutter is an abnormality in the beating of the heart. Such abnormalities, whether in the rhythm or speed of the heartbeat, are known as arrhythmias.
The heart is a muscle that pumps the blood through the body.
- Each beat of the heart is a very rapid series of two contractions.
- The first contraction is in the upper chambers, the atria; the second contraction is in the lower chambers, the ventricles.
- The atria receive blood back into the heart and pump it into the ventricles; the ventricles pump the blood out into the aorta, which feeds all the blood vessels to the body.
The beating of the heart is controlled by electrical impulses.
- Under normal circumstances, these impulses are generated by the heart's "natural pacemaker," the sinoatrial (SA) or sinus node, which is located in the right atrium.
- The impulse travels across the atria, generating a contraction.
- It pauses very briefly at the atrioventricular (AV) node, which is located in the upper part of the muscular wall between the two ventricles. This delay gives the blood time to move from the atria to the ventricles.
- The impulse then moves down and through the ventricles, generating the second ventricular contraction that pumps the blood out of the ventricles.
Atrial flutter occurs when an abnormal conduction circuit develops inside the right atrium, allowing the atria to beat excessively fast, about 250-300 beats per minute.
- These rapid contractions are slowed when they reach the AV node, but are still too fast (typically about 150 beats per minute, or every other atrial beat getting through the AV node to the ventricles).
- This type of rhythm is called tachycardia. Because atrial flutter comes from the atria, it is called a supraventricular (above the ventricles) tachycardia.
The main danger of atrial flutter is that the heart does not pump blood very well when it is beating too fast.
Atrial flutter can come and go; it is then known as paroxysmal atrial flutter. An episode of atrial flutter usually lasts hours or days. Less often, atrial flutter is more or less permanent and is known as persistent atrial flutter.
With proper treatment, atrial flutter is rarely life threatening. Complications of atrial flutter can be devastating, but they usually can be prevented with treatment.