An embolism is?

• A. A thrombus that remains stationary at the original site
• B. A thrombus that breaks loose to become an embolism and occlude downstream blood flow
• C. Air in the bloodstream
• D. A dissolved clot

Answer: (B)

An embolism is a detached intravascular mass that travels through the bloodstream and lodges in a downstream vessel, causing obstruction. The most common source is a thrombus that has broken free from its site and becomes an embolus, traveling until it occludes a vessel and impairs blood flow. This traveling blockage can lead to ischemia or infarction in the tissues it affects.

If a thrombus stays attached at its original site, it isn’t an embolism. An air embolism is a specific type of embolism caused by air entering the bloodstream, but the general concept centers on a detached mass that travels. A dissolved clot has ceased to exist as an embolus.