Which arrhythmia is characterized by very fast beating of the atria?

Atrial flutter is characterized by a rapid and organized beating of the atria, typically between 240 to 340 beats per minute. This arrhythmia occurs due to a reentrant circuit in the right atrium that leads to a rapid firing of impulses, resulting in a "sawtooth" pattern on an ECG, commonly referred to as "F-waves." The organized nature of atrial flutter sets it apart from other arrhythmias, as the atrial contractions are relatively regular compared to the chaotic electrical activity seen in atrial fibrillation or the more rapid and less organized activity found in atrial tachycardia.

In contrast, atrial fibrillation is characterized by rapid and irregular beating of the atria, resulting in an ineffective and chaotic contraction. Atrial tachycardia refers to any rapid rhythm originating from the atria but can vary in rate and organization, typically resulting in a heart rate over 100 beats per minute, but it is not limited to the organized patterns observed in flutter. Ventricular tachycardia is a different form of tachycardia originating from the ventricles and indicates a more severe situation often requiring immediate medical attention. These characteristics clarify why atrial flutter is the correct identification for