What ECG feature indicates atrial fibrillation in a patient?

Atrial fibrillation is characterized by a unique pattern on an electrocardiogram (ECG) that is essential for identification. The absence of discrete P waves is a significant feature because, in atrial fibrillation, the atria do not contract effectively, and thus no clear P waves are generated. Instead, what you observe are irregularly irregular QRS complexes, resulting from rapid, chaotic electrical activity in the atria. This leads to a lack of a predictable rhythm in the ventricular response.

The presence of irregularly irregular QRS complexes signifies that the electrical impulses reaching the ventricles are coming at varying intervals, reflecting the loss of coordinated atrial contractions that typically optimize filling of the ventricles. This chaotic electrical activity is what differentiates atrial fibrillation from other arrhythmias where P waves would still be present or where the QRS complexes would exhibit a more regular pattern.

In contrast, the other options provided would not accurately depict atrial fibrillation. Discrete P waves would suggest a normal sinus rhythm or other atrial flutter patterns, while regularly irregular QRS complexes and normal sinus rhythm indicate more organized atrial activity, which is not found in atrial fibrillation. Hence, the identification of atrial fibrillation relies on recognizing