Circulatory system
A clot typically causes blocked blood flow strokes. These are the most common, causing nearly 90 percent of all strokes. If you've had a stroke, you are at a higher risk of having a second stroke or heart attack.
It affects the arteries leading to and within the brain. A stroke occurs when a blood vessel that carries oxygen and nutrients to the brain is either blocked by a clot or bursts. When that happens, part of the brain cannot get the blood (and oxygen) it needs, so it starts to die.