Classification of Atrial Flutter

It depends upon the anatomical location and direction of the re-entry circuit.
1-Typical Atrial Flutter (Common, or Type I At rial Flutter)
Involves the IVC & tricuspid isthmus in the reentry circuit. Can be further classified based on the direction of the circuit:
A-Anticlockwise Reentry. This is the commonest, form of atrial flutter (90% of cases). Retrograde atrial conduction produces:
Inverted flutter waves in leads II,III, aVF
Positive flutter waves in V1 – may resemble upright P waves
B-Clockwise Reentry. This uncommon variant produces the opposite pattern:
*Positive flutter waves in leads II, III, aVF
*Broad, inverted flutter waves in V1
2-Atypical Atrial flutter (Uncommon, or Type II Atrial Flutter)
*Does not fulfil criteria for typical atrial flutter.
*Often associated with higher atrial rates and rhythm instability…
*Less amenable to treatment with ablation.