Diseases of the Blood Vessels - Embolism

An embolus, or thrombus that has broken away into the bloodstream, is, as we have seen, sometimes the direct cause of a stroke. A heart attack may also cause a stroke. Bacterial action may soften a thrombus so that it separates into fragments and breaks free from its wall anchorage. Thrombi are not the only source of emobli; any free-floating mass in the bloodstream, be it an air bubble, clumps of fat, knots of cancer cells, or bacteria, can prove dangerous.

Usually, however, emboli originate as thrombi in the veins, especially the leg veins. Breaking free, the clump of clot material wanders into the bloodstream to be carried towards the right chamber of the heart and then onward into the lungs, unless dissolved before that. Once in the pulmonary arteries there is a growing threat that the moving mass will catch in one of the smaller branches of the lung circulation. This life-threatening blockage is called a pulmonary embolism .

This disorder takes at least 50,000 lives a year; most occur during or following prolonged periods of hospitalization and bed rest. The lack of activity slows the blood flow and increases the danger of thrombi—and ultimately emboli. Prevention requires getting the patient out of bed as soon and as often as possible to stimulate leg circulation. The non-ambulatory patient, meanwhile, is encouraged to move his legs by raising them, or changing positions so as to step up blood flow.

The detection of a large embolus—symptoms include shortness of breath and chest pains—may require emergency surgery for removal. In most instances, however, treatment means administering anticoagulants to prevent new clots from emerging while allowing the body to rid itself of the embolus.