Types of emboli
Also known as: embolus, emboli
An embolism occurs when material travels through the bloodstream and lodges in a vessel, blocking blood flow. Most emboli are dislodged blood clots, but fat, air, amniotic fluid, tumor fragments, and infected material can all embolize.
An embolus is any intravascular material — solid, liquid, or gas — that is carried by the blood to a site distant from its origin, where it lodges and obstructs flow. The resulting blockage is an embolism, and the downstream tissue is deprived of oxygen, which can cause ischemia or infarction. An embolus differs from a thrombus in that a thrombus forms and stays at one site, while an embolus travels.
The most common type by far is the thromboembolism, a fragment of a blood clot that breaks free. The classic example is a pulmonary embolism: a deep vein thrombosis in the leg dislodges, travels through the right heart, and wedges in the pulmonary arteries. Emboli arising in the left heart or arteries (for example, with atrial fibrillation) can travel to the brain and cause stroke, or to the mesenteric vessels and cause acute mesenteric ischemia.
Other important types include fat emboli after long bone fractures (classically presenting with hypoxia, neurologic changes, and a petechial rash), air emboli from trauma, surgery, or improperly handled IV lines and central catheters, amniotic fluid emboli during labor and delivery, septic emboli from infected heart valves, and tumor emboli. A paradoxical embolus crosses from the venous to the arterial circulation through a cardiac defect such as a patent foramen ovale.
The USMLE Step 1 tests the types of emboli, their classic clinical vignettes, and complications like mesenteric ischemia, while the NCLEX emphasizes nursing implications — recognizing embolic complications of devices, procedures, and immobility, and preventing air embolism during IV and central line care.
Key takeaways
- An embolism is a traveling intravascular mass that lodges in a vessel and obstructs blood flow.
- Thromboemboli are most common; a DVT that travels to the lungs causes pulmonary embolism.
- Fat emboli follow long bone fractures; air emboli complicate lines and procedures; amniotic fluid emboli occur during delivery.
- A paradoxical embolus reaches the arterial circulation through a defect like a patent foramen ovale.
- USMLE Step 1 tests embolus types and vignettes; the NCLEX tests prevention and recognition of embolic complications.