An embolism is an abnormal mass in the bloodstream that is swept along until it obstructs a blood vessel. The most common type of embolism is a blood clot, or thrombus. Other types include air bubbles, clumps of bacteria, undissolved particles of drugs, and bone-marrow fragments, as from a fracture.
All parts of the body are vulnerable to embolisms. Blood clots that form at the site of surgery or an injury may be dislodged by movement and swept away. If a large embolism is swept to the lungs, it lodges in a branch of the pulmonary artery, obstructing the flow of blood and sometimes causing sudden death. Smaller pulmonary embolisms cause shallow respiration, a reduction in the oxygenation of the blood, a lowering of the arterial blood pressure, and possibly an overloading of the heart's pumping capacity. If a clot forms inside the heart- as may happen in rheumatic heart disease or endocarditisit may be carried to an artery of the brain, causing a stroke. Heart attacks themselves may result from embolisms in the coronary arteries that supply the heart muscle. If the affected muscle segment dies, the heart may no longer function properly.
The treatment of an embolism may require emergency surgery to remove the mass before the tissues supplied by the obstructed blood vessel are seriously damaged. Anticoagulants, such as heparin and Coumadin, may be administered to prevent additional clots from forming. If a particular part of the body, such as a leg, has some disorder in which clots are readily formed, the major vein leading from that area may be closed surgically to prevent the clots from passing through.