Atrial Macro-Reentrant Rhythms (Flutter)

This section will provide an overview of atrial arrhythmias involving large, so-called "macro"-reentrant circuits, also known as atrial flutter. 

Topics to be covered:

• Typical atrial flutter, due to re-entry around the tricuspid annulus, involving the cavotricuspid isthmus as the slow pathway. We cover the ECGs of both the clockwise and counterclockwise typical flutters. We will also cover the initiation and termination of the rhythm. Other topics will include the following:

  • The differential diagnosis of atrial flutter, including sinus tachycardia or atrial tachycardia, and "faux flutter" due to rhythmic artefact.

  • Atrial flutter with varying degrees of atrioventricular block, such as fixed-ratio blocks (i.e. 2:1, 3:1), variable block, high grade block causing "slow flutter", and complete heart block.

  • Atrial flutter with 1:1 conduction and its causes, most commonly being the presence of an accessory tract.

  • Atrial flutter with aberrancy due to bundle branch block causing a wide-complex tachycardia mimicking ventricular tachycardia.

  • The relationship between atrial flutter and atrial fibrillation (also covered in the atrial fibrillation section).

  • Pseudo-ST elevation: Atrial flutter mimicking ST elevation without the presence of any cardiac ischemia.

• Atypical atrial flutter, or flutter not involving the pathway defined by "typical" atrial flutter, usually related to atrial scarring from disease or surgery. We will discuss how to cursorily differentiate this from typical flutter on the ECG, while stressing the challenges associated with identifying this rhythm.