What is the most common cause of ischemic stroke?

Atrial fibrillation is indeed the most common cause of ischemic stroke. This condition is characterized by an irregular and often rapid heart rate that can lead to poor blood flow. In atrial fibrillation, blood can pool in the atria of the heart, increasing the risk of clot formation. If a clot breaks free, it can travel to the brain, resulting in an ischemic stroke, which occurs when a blood vessel supplying blood to the brain becomes obstructed.

While hypertension is a major risk factor for stroke and contributes significantly to the development of various cardiovascular diseases, it is the mechanism of clot formation in atrial fibrillation that directly leads to ischemic events. Diabetes can also increase the risk of stroke through various vascular complications, but it is not as direct a cause of ischemic stroke as atrial fibrillation. Cerebral aneurysms are more associated with hemorrhagic strokes rather than ischemic strokes, as they can lead to bleeding in the brain rather than obstruction of blood flow.

In summary, atrial fibrillation is specifically linked to the mechanism that leads to ischemic strokes through the formation of embolic clots, making it the most common cause among the options provided.