6th March 2024

Atrial Flutter

In contrast to the chaotic atrial activity of AF, flutter is characterised by a more organised arrhythmia, typically with a counter-clockwise macro reentry circuit occurring within the right atrium. This circuit is seen on the ECG as flutter waves, which have a characteristic saw-tooth pattern in V1 and negative flutter waves inferiorly (leads II, III, AVF). These waves occur at a rate of around 300/min, which is dampened by the AV node, which may result in a 2:1, 3:1, or 4:1 block giving a ventricular rate of 150, 100 or 75 bpm, respectively. In the presence of a variable block, the rhythm may be irregular. 

Management is similar to AF and the principles of thromboprophylaxis remain the same for elective cardioversions as outlined for AF. It is useful to calculate the CHA2DS2-VASc score and consider anticoagulation in those with a high score to prevent thromboembolic events, as patients may experience both flutter and fibrillation episodes.

Rate control is typically difficult to attain with atrial flutter, which tends to respond less to digoxin. Initially, a beta blocker or rate limiting calcium channel blocker may be used. Atrial flutter responds well to electrical cardioversion, requiring very low energy levels to restore sinus rhythm; but in view of stroke risk, similar recommendations as in AF are advocated with respect to three-weeks of uninterrupted anticoagulation prior to cardioversion for onset >48 hours. 

Typical atrial flutter is often successfully definitively managed with radio-frequency ablation within a localised area between the tricuspid valve annulus and the inferior vena cava (the cavo-tricuspid isthmus) which is key to the macro reentry circuit. First attempts are often 90% successful at attaining curative intent.