Atrial flutter is an AV node-independent intra-atrial macro-reentry rhythm, in which the atrial anatomy sustains a loop of continuous depolarization, often around the tricuspid valve annulus in the right atrium. Atrial flutter can be paroxysmal or chronic and may be associated with extremely rapid ventricular response rates. Because not every one of the rapid atrial beats propagates successfully to the ventricles, variable degrees of AV block often modify AV conduction, which changes between 1:1 and 3:1 or 2:1. Atrial flutter often induces electrical remodeling and thereby can serve as a precursor to atrial fibrillation.
The movie illustrates a heart with several beats of atrial flutter, which are manifested as the increased rate of contraction in the upper chambers of the heart and lack of synchrony with the larger ventricles below. The animation shows a visualization of the repetitive electrical activity in the upper chambers of the heart as a spiral wave. The ventricles contract less often because the heart's conduction system under normal circumstances does not allow such rapid atrial rhythms to be passed to the ventricles. The yellow color in the ventricles indicates electrical activation, which precedes ventricular contraction.