What characterizes Atrial Fibrillation?

Atrial Fibrillation (AF) is characterized by irregular contraction patterns in the atria. In this arrhythmia, the electrical signals in the atria are disorganized and chaotic, leading to rapid and irregular atrial activity. This results in ineffective atrial contractions, which can contribute to the risk of thrombus formation and stroke. The irregular patterns mean that there is no consistent rhythm to the heartbeat, which can be readily observed on an electrocardiogram (ECG) as an absence of distinct P waves and an irregularly irregular ventricular response.

The other options present patterns that do not align with the characteristics of Atrial Fibrillation. For instance, regular atrial contractions imply a stable and rhythmic electrical conduction, which is antithetical to the nature of AF. High-frequency blood flow in the ventricles is not a defining feature of AF, and synchronized atrial and ventricular depolarization suggests a normal conduction pathway, which is disrupted in Atrial Fibrillation. Thus, the key characteristic of Atrial Fibrillation lies in its irregular contraction patterns in the atria, distinguishing it from other types of arrhythmias.