An embolus is a detached, traveling mass that lodges in a blood vessel, causing a blockage known as an embolism. This is distinct from a thrombus, which is a stationary blood clot that forms and remains in one location within a blood vessel. An embolus, conversely, originates in one part of the body and travels to another, leading to a blockage at a distant site.
Types of Emboli
The most frequent type of embolus is a thromboembolus, which is a piece of a blood clot that has broken free from its original location. When this detached clot lodges elsewhere, it obstructs blood flow.
Other materials can also form emboli, though they are less common. Fat emboli consist of fat globules that enter the circulation after a major injury such as the fracture of a large bone. Air emboli can occur if air bubbles are introduced into the bloodstream, sometimes during surgical procedures or from intravenous lines. Septic emboli, which are clumps of bacteria and infected tissue, can break off and travel through the blood. A rare type, an amniotic fluid embolus, can occur if amniotic fluid enters the mother’s circulation during childbirth.
Medical Conditions Caused by an Embolus
When an embolus obstructs a blood vessel, it can lead to serious medical conditions by cutting off the blood supply to tissues. A pulmonary embolism happens when an embolus travels to the lungs and blocks an artery there, leading to symptoms like sudden shortness of breath and chest pain. If an embolus travels to the brain and lodges in a cerebral artery, it can cause an ischemic stroke by depriving brain cells of oxygen. The specific neurological symptoms that result, such as difficulty speaking or weakness, depend on the area of the brain affected.
An embolus can also block one of the coronary arteries that supply blood to the heart, resulting in a myocardial infarction, or heart attack. A peripheral artery embolism occurs when a blockage happens in a vessel supplying a limb, causing sudden pain and coldness in the affected area.
Associated Risk Factors
Several conditions increase the likelihood of an embolus forming. A significant risk factor is deep vein thrombosis (DVT), where blood clots form in the deep veins of the legs. A piece of one of these clots can break off and travel to other parts of the body, most commonly the lungs. Atrial fibrillation, an irregular and often rapid heart rhythm, can cause blood to pool in the heart’s upper chambers, leading to the formation of clots that can travel to the brain.
Prolonged periods of immobility, such as during long hospital stays or extended travel, also contribute to the formation of blood clots due to slowed blood flow. Major surgery, certain types of cancer, and severe physical trauma are also risk factors.
Diagnosis and Treatment
Diagnosing an embolism promptly is important for effective treatment. Doctors use several imaging techniques to locate the blockage. A computed tomography (CT) scan is frequently used to create detailed images of the blood vessels. For a suspected pulmonary embolism, a ventilation-perfusion (V/Q) scan may be used to assess air and blood flow in the lungs. An ultrasound is often the first step in diagnosing DVT in the legs.
Treatment focuses on restoring blood flow and preventing future clots. Anticoagulant medications, or blood thinners, are prescribed to prevent existing clots from growing and new clots from forming. In urgent situations, thrombolytic therapy uses powerful “clot-busting” drugs to dissolve the embolus. For large blockages, a surgical procedure called an embolectomy may be performed to physically remove the embolus.