Atrial flutter is a common rhythm disturbance where the top chambers (atria) beat at about 300 beats per minute. This rate is too fast for them to effectively help fill the left ventricle, which pumps the blood to the body. Therefore, the efficiency of the heart pumping blood is diminished.
Fortunately, not all of the 300 beats per minute in the atria pass down the normal pathway (the AV node) to the left ventricle, or the pulse would also be at 300 and a cardiac arrest could occur. Usually, the AV node filters out every other beat, which makes the pulse 150 beats per minute or so. If the AV node filters more beats, the heart rate could be as low as 100, 75 or 60 or even slower.
Most atrial flutter arises in the right atrium. The heartbeat races in a circle around the tricuspid valve between it and a ridge called the crista terminalis. It can race counter-clockwise or more rarely clockwise. This is called “typical” atrial flutter. More rarely, atrial flutter may involve a more complicated circuit in people that have had open-heart surgery or other ablation procedures that produced scarring in the heart.
Some patients with atrial flutter are at increased risk of a stroke, so it is important to recognize atrial flutter and decide on treatment. Other people with atrial flutter that goes untreated may develop congestive heart failure, a serious weakness of the left ventricle.