Atrial fibrillation is characterized by the absence of what feature on an ECG?

Atrial fibrillation is characterized by the absence of P waves on an electrocardiogram (ECG). In a normal ECG, P waves represent atrial depolarization, which occurs prior to the QRS complex. However, during atrial fibrillation, the electrical activity in the atria is disorganized and chaotic, preventing the formation of distinct P waves. Instead, the ECG may show irregularly timed QRS complexes that follow the chaotic waveform created by the fibrillating atria. This irregularity is a hallmark of atrial fibrillation, making the absence of P waves a key diagnostic feature.

In contrast, T waves, QRS complexes, and U waves are still present in the ECG of a patient with atrial fibrillation, though their morphology and timing may be affected by the overall condition. QRS complexes, which represent ventricular depolarization, will still appear but in an irregular pattern due to the rapid and varied impulses transmitted to the ventricles. T waves, responsible for ventricular repolarization, and U waves, which are less common and associated with certain arrhythmias or conditions, will also continue to be recorded in atrial fibrillation. Thus, recognizing the absence of P waves helps differentiate atrial fibr