- Atrial fibrillation is characterized by disorganized atrial electrical activity resulting in an irregularly irregular ventricular response.
- This leads to the hallmark clinical presentation of irregularly irregular palpitations on physical examination and ECG.
- Unlike other arrhythmias, the absence of any repeating pattern in rhythm differentiates atrial fibrillation and underlies its typical irregular pulse.
- This key feature aids in diagnosis and distinguishes it from rhythms like atrial flutter or ventricular tachycardia which have more regular patterns.

Reference: Davidson’s Principles and Practice of Medicine, 24th Edition, Chapter: Disorders of the Heart Rhythm, Page 343.