Which arrhythmia is characterized by a persistently fast heart rate with varying intervals?

Atrial fibrillation is characterized by a persistently fast heart rate and the presence of varying intervals between heartbeats. In this arrhythmia, the atria do not contract effectively, leading to a chaotic and irregular rhythm. Instead of the structured contractions seen in normal sinus rhythm, the electrical impulses in the atria fire erratically, resulting in an irregularly irregular ventricular response. This irregularity in the intervals between the QRS complexes on an electrocardiogram is a hallmark of atrial fibrillation. The result is often a rapid heartbeat, which can vary depending on the response of the AV node and the overall conduction through the heart.

In contrast, junctional rhythm arises from the AV node and usually features a more regular rhythm without the rapid, chaotic fluctuations seen in atrial fibrillation. Normal sinus rhythm indicates a healthy heart rhythm with regular intervals and a normal rate, showing no signs of the variability found in atrial fibrillation. Atrial flutter, while it can also involve rapid heart rates, typically presents with a more organized rhythm, characterized by "sawtooth" waves, predominantly affecting the atria and leading to a more regular pattern compared to the irregular nature of atrial fibrillation. Thus, the chaotic nature and variation