What ECG pattern is associated with atrial fibrillation?

Atrial fibrillation is characterized by an irregularly irregular rhythm where there are no identifiable P waves. This occurs due to the chaotic electrical activity in the atria, which prevents the formation of consistent and discernible P waves. Instead of the normal atrial contraction seen in a sinus rhythm, atrial fibrillation leads to the quivering of the atrial muscle, resulting in an unpredictable and disorganized rhythm.

In atrial fibrillation, the ventricular response can vary widely as well, leading to the irregular appearance of the R-R intervals on the ECG. The absence of P waves and the irregularity are key identifying features that help differentiate atrial fibrillation from other arrhythmias, making option D the correct representation of the ECG pattern associated with this condition.