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.