Pathophysiology
Clinical meaning
Unlike A-fib's multiple chaotic circuits, atrial flutter involves a single macro-reentrant circuit, typically circling around the tricuspid valve annulus in the right atrium. This circuit fires at approximately 300 bpm, producing the characteristic sawtooth flutter waves on ECG. The AV node cannot conduct all 300 impulses, so it blocks in a fixed ratio — most commonly 2:1 (ventricular rate around 150), but also 3:1, 4:1, or variable. The regular sawtooth pattern and fixed conduction ratio distinguish flutter from fibrillation.