We know, classical Atrial flutter (Also referred to as typical /Common AF) records saw toothed F waves due to continuous atrial electrical activity across a macro- reentrant circuit within right atrium.
Though this saw tooth pattern is easily recognised , it’s often difficult to say whether the saw is facing upwards or downwards ?
ie Is the flutter waves are inverted or upright ?
The general rule is the shallow stroke (one with a lesser slope) is to be termed as antegrade / initial deflection that will determine the direction of flutter waves.
This is because , the forward limb traverses the slow path of the circuit namely the cavo-tricuspid Isthmus, it then ascends up in the inter atrial septum (There by inscribing inverted F waves in leads 2,3,aVF .The return circuit is relatively fast, crossing the antero -lateral free wall right atrium and hence the later half saw tooth has a sharp deflection )
In Reverse typical flutter the flutter waves are upright (with a shallow slope ) in inferior leads but still uses the cavo- tricuspid Isthmus
* Note: In lead the polarity of F waves in V1 it will be opposite of that of inferior leads.
Why should we bother about direction of flutter waves ?
It may not be important for those hifi EP guys who can ablate complex arrhythmia with intra cardiac GPS catheters and accurate electro anatomic mapping system. Still , the surface ECG always help us understand the basic circuits of flutter.
Reverse typical flutter should not be confused with atypical flutter where typical saw tooth waves are uncommon.The later group is termed as atypical atrial flutter that arises from various other focus including left atrium.