Which arrhythmia is classified as a type of atrial tachycardia?

Atrial flutter is classified as a type of atrial tachycardia due to its characteristic rapid heart rate originating in the atria, particularly the right atrium. In atrial flutter, the atria can beat at rates between 240 to 340 beats per minute, leading to a distinct "sawtooth" pattern observed on an electrocardiogram (ECG). This arrhythmia results from a reentrant circuit, typically around the tricuspid valve, causing the atrial muscle to contract rapidly but in a more organized manner than some other forms of tachycardia.

In contrast, other options represent different types of cardiac issues. Ventricular fibrillation is a chaotic electrical activity in the ventricles, leading to ineffective pumping of blood and is not classified as atrial tachycardia. Bradycardia refers to a slower than normal heart rate of less than 60 beats per minute and does not fall under the category of tachycardia. Premature ventricular contractions (PVCs) are extra, abnormal heartbeats originating in the ventricles and are not classified as atrial arrhythmias. These differences highlight why atrial flutter is the correct answer among the presented options.