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In an embolic stroke, blockage of a blood vessel in the brain is caused by a blood clot that forms elsewhere in the body. The ability of the blood to form clots is an important function for the body to repair itself. Blood contains several types of cells, including red blood cells that carry oxygen and carbon dioxide, white blood cells that fight infection and platelets that form the clots.
A blood clot is formed when platelets aggregate at an area of tissue damage. However, sometimes clots form in places they are not supposed to, thereby causing damage. There are two medical terms for blood clots; a thrombus is a blood clot that forms in blood vessels or in the heart that does not move to another part of the body. Once the blood clot, or even a piece of the clot breaks apart and moves through the body, it is called an embolus. - When there is an injury, platelets are called to the damaged area. These activated platelets release chemicals that activate a series of clotting factors, including fibrin which is a clotting protein. This protein links with itself and the platelets to form the clot. A blood clot can also form where blood is stagnant or not moving.
- Atrial Fibrillation is when the upper chambers of the heart beat out of synchronization with the lower chambers. This can result in irregular or rapid heartbeat. It can also lead to the formation of small pools of blood that remain stagnant, which can result in the formation of small blood clots along the walls of the upper chambers of the heart. These clots can then break off, or embolize, and travel through the blood. The blood vessels lead to the brain, where they can become lodged, cutting off the blood supply to the brain resulting in an embolic stroke.
- Lambl's excrescences are small filamentous tumor-like growths that form on or near the valves of the heart. They start as small thromi (blood clots), which do have the ability to produce emboli. These emboli can then travel to the brain, causing an embolic stroke.
- Since the majority of the blood clots, or emboli, that cause an embolic stroke originate in the heart, patients should live a healthy lifestyle that prevents heart disease. Patients with atrial fibrillation can benefit from anticoagulation treatment by using warfarin. Aspirin therapy, which helps thin the blood, has also proven to aid in the prevention of clots due to atrial fibrillation. Some patients may also benefit from taking antiarrhythmic medications.
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To determine the risk of an embolic stroke, or even provide diagnosis for patients who are or have experienced an embolic stroke, doctors can use the following tests:
Carotid Ultrasound -- sends high frequency sound waves through the tissues of the neck producing an image that can reveal narrowing or clotting of the carotid artery.
Arteriography -- the insertion of a small catheter through an incision and into the carotid artery where dye can be injected to produce an image.
Echocardiograph -- an ultrasound technology specifically designed for the heart. The images can reveal the presence of emboli before they leave the heart and travel to the brain.
