How does atrial fibrillation typically appear on an ECG?

Atrial fibrillation typically presents on an ECG as an irregularly irregular rhythm, which is characterized by the absence of distinct P waves. This results from the chaotic electrical activity in the atria, causing them to quiver instead of contract effectively. The irregularity in the R-R intervals (the intervals between successive QRS complexes) is a hallmark feature of atrial fibrillation. The QRS complexes may appear normal, indicating that the electrical signals are still being conducted through the ventricles, but their timing is erratic due to the lack of coordinated atrial contraction.

In contrast, a regular rhythm with P waves would suggest a normal sinus rhythm or another type of organized atrial rhythm, which is not consistent with atrial fibrillation. A fast regular rhythm accompanied by distinct QRS complexes could suggest a different type of tachycardia, such as atrial flutter or paroxysmal supraventricular tachycardia. A flat line with no electrical activity signifies asystole or severe dysfunction, which is not characteristic of atrial fibrillation.