The clot is carried by the bloodstream until it lodges in an artery leading to or in the brain, blocking the flow of blood. The most common cause of these emboli is blood clots that form during atrial fibrillation. In atrial fibrillation the two small upper chambers of the heart, the atria, quiver instead of beating effectively. Blood isn't pumped completely out of them when the heart beats, allowing the blood to pool and clot. About 15 percent of strokes occur in people with atrial fibrillation.
High levels are a large factor in clogging arteries.
Your blood pressure is checked each time you donate and cholesterol levels are checked periodically.