Atrial fibrillation is a common cardiac arrhythmia characterised by rapid, irregular electrical activity in the atria, leading to ineffective atrial contraction and an irregularly irregular ventricular response. It matters clinically because it increases the risk of stroke and heart failure due to impaired cardiac output and thrombus formation in the atria. One key complication is embolic stroke, which arises from atrial thrombi dislodging and occluding cerebral arteries.