What is atrial flutter? Cardiology Basics

What is atrial flutter? Cardiology Basics

Atrial flutter is a fast and organized arrhythmia originating from the atria. In this way it is different from the commoner atrial fibrillation which is quite fast but irregular rhythm originating from the atria. It shares the risk of thrombus formation in the atria and needs anticoagulants, like atrial fibrillation. Atrial flutter commonly arises from the right atrium. It can also arise from the left atrium sometimes.

Though the atrial rate is typically around 300/minute, the whole of it does not get conducted to the ventricles. The AV node reduces the number of impulses conducted to the ventricles. When there is only 2:1 conduction to the ventricles, the ventricular rate will be 150/minute. At this rate it may be mistaken for a supraventricular tachycardia as the flutter waves may not be evident, being superimposed on QRS and T waves.

Atrial flutter can be seen in the ECG as ‘saw tooth shaped’ flutter waves representing the organized atrial activity. This is easily seen when the conduction block is more than 2:1 so that there is enough space between the QRS complexes and T waves to show the flutter waves. P waves are replaced by flutter waves in atrial flutter. They are also called as F waves sometimes.

When atrial flutter occurs in a neonate, the flutter rate is higher, just like the normal heart rate in the neonate which is higher than in the adult. In the ECG shown, atrial rate is above 400/minute and ventricular rate above 200/minute. This also shows the 2:1 AV conduction. You can also see that it is more difficult to notice the flutter waves in this case.

Atrial flutter can be treated initially with antiarrhythmic medications. If there is no response, it can be easily terminated by electrical cardioversion. As atrial flutter is due to a large reentrant circuit (macro-reentry), it is highly sensitive to cardioversion, and needs only relatively low energy compared to atrial fibrillation. If there is any underlying structural heart disease or electrolyte abnormality , it has to be treated.

There is an advanced form of treatment known as radiofrequency catheter ablation which can be used to prevent recurrence of atrial flutter in the long term. An electrophysiology study is done using multiple intracardiac electrodes to identify the flutter circuit. Usual site for ablation of atrial flutter is the cavotricuspid isthmus in the lower part of right atrium. Radiofrequency catheter ablation gives long lasting results for most cases of atrial flutter, with low procedural risk.