View source for Embolism

{{Short description|Blockage of a blood vessel by a circulatory mass (embolus)}}
{{About|the vascular phenomenon|other uses|Embolism (disambiguation)}}
{{Distinguish|ebullism|aneurysm}}
{{Infobox medical condition (new)
| name            = Embolism
| image        = Embolization kidney.jpg
| caption      = [[Micrograph]] of embolic material in the artery of a kidney. The kidney was surgically removed because of [[kidney cancer|cancer]]. [[H&E stain]].
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An '''embolism''' is the lodging of an [[embolus]], a blockage-causing piece of material, inside a [[blood vessel]].<ref>{{cite book|last1=Dorland's|title=Dowland's Illustrated Medical Dictionary |date=2012|publisher=Elsevier|isbn=978-1-4160-6257-8|page=606|edition=32nd}}</ref> The embolus may be a blood clot ([[thrombus]]), a fat globule ([[fat embolism]]), a bubble of air or other gas ([[air embolism|gas embolism]]), [[amniotic fluid]] ([[amniotic fluid embolism]]), or [[foreign body|foreign material]].
An embolism can cause partial or total blockage of [[blood flow]] in the affected vessel.<ref>Britannica Concise Encyclopedia 2007</ref> Such a blockage ([[vascular occlusion]]) may affect a part of the body distant from the origin of the embolus. An embolism in which the embolus is a piece of thrombus is called a [[thromboembolism]].
An embolism is usually a pathological event, caused by illness or injury. Sometimes it is created intentionally for a therapeutic reason, such as to [[hemostasis|stop bleeding]] or to kill a cancerous tumor by stopping its blood supply. Such therapy is called [[embolization]].
== Classification ==
There are different types of embolism, some of which are listed below.
Embolism can be classified based on where it enters the circulation, either in [[arteries]] or in [[veins]]. Arterial embolism are those that follow and, if not dissolved on the way, lodge in a more distal part of the [[systemic circulation]]. Sometimes, multiple classifications apply; for instance a [[pulmonary embolism]] is classified as an arterial embolism as well,<ref name="medlineplus">[https://www.nlm.nih.gov/medlineplus/ency/article/001102.htm MedlinePlus > Arterial embolism] Sean O. Stitham, MD and David C. Dugdale III, MD. Also reviewed by David Zieve, MD. Reviewed last on: 5/8/2008. Alternative link: [https://web.archive.org/web/20070220214959/http://www.umm.edu/ency/article/001102.htm]</ref> because the clot follows the [[pulmonary artery]] carrying deoxygenated blood away from the heart. However, pulmonary embolism is generally classified as a form of venous embolism, because the embolus forms in veins, e.g. [[deep vein thrombosis]].{{cn|date=October 2021}}
=== Arterial ===
{{Main|Arterial embolism}}
[[Arterial embolism]] can cause occlusion in any part of the body. It is a major cause of [[infarction]] (tissue death from blockage of the blood supply).<ref>[http://www.mdguidelines.com/arterial-embolism-and-thrombosis MDGuidelines > Arterial Embolism And Thrombosis] {{Webarchive|url=https://web.archive.org/web/20180202063012/http://www.mdguidelines.com/arterial-embolism-and-thrombosis |date=2018-02-02 }} From ''The Medical Disability Advisor'' by Presley Reed, MD. Retrieved on April 30, 2010</ref>
An embolus lodging in the brain from either the [[heart]] or a [[carotid artery]] will most likely be the cause of a [[stroke]] due to [[ischemia]].<ref>{{Cite web |title=A Neurosurgeon's Guide to Stroke Symptoms, Treatment and Prevention |url=https://www.aans.org/ |access-date=2023-11-25 |website=American Association of Neurological Surgeons |language=en}}</ref>
An arterial embolus might originate in the heart (from a thrombus in the [[left atrium]], following [[atrial fibrillation]] or be a septic embolus resulting from [[endocarditis]]). Emboli of [[heart|cardiac origin]] are frequently encountered in clinical practice.  Thrombus formation within the atrium occurs mainly in patients with [[mitral valve]] disease, and especially in those with [[mitral valve]] [[stenosis]] (narrowing), with [[atrial fibrillation]] (AF).  In the absence of AF, pure mitral regurgitation has a low incidence of [[thromboembolism]].{{citation needed|date=February 2021}}
The risk of emboli forming in AF depends on other risk factors such as age, [[hypertension]], [[diabetes]], recent heart failure, or previous stroke.
Thrombus formation can also take place within the [[Ventricle (heart)|ventricles]], and it occurs in approximately 30% of anterior-wall [[myocardial infarction]]s, compared with only 5% of inferior ones. Some other risk factors are poor ejection fraction (<35%), size of infarct, and the presence of AF. In the first three months after infarction, left-ventricle [[aneurysm]]s have a 10% risk of emboli forming. Patients with [[prosthetic]] valves also carry a significant increase in risk of thromboembolism. Risk varies, based on the valve type (bioprosthetic or mechanical); the position (mitral or aortic); and the presence of other factors such as AF, left-ventricular dysfunction, and previous emboli{{cn|date=October 2021}}.
Emboli often have more serious consequences when they occur in the so-called "end circulation": areas of the body that have no redundant blood supply, such as the brain and [[heart]].{{cn|date=October 2021}}
=== Venous ===
{{Further|Pulmonary embolism|thrombosis prophylaxis}}
[[File:3D Medical Animation still shot Pulmonary Embolism.jpg|alt=3D Medical Animation still shot showing Pulmonary Embolism|thumb|3D Medical Animation still shot showing Pulmonary Embolism]]
Assuming a normal circulation, an embolus formed in a systemic [[vein]] will always impact in the lungs, after passing through the right side of the heart. This will form a [[pulmonary embolism]] that will result in a blockage of the [[pulmonary artery|main artery of the lung]] and can be a complication of [[deep-vein thrombosis]]. The most common sites of origin of pulmonary emboli are the [[femoral vein|''femoral'' veins]]. The deep veins of the calf are the most common sites of actual thrombi.{{citation needed|date=February 2021}}
=== Paradoxical (venous to arterial) ===
{{Main|Paradoxical embolism}}
In paradoxical embolism, also known as crossed embolism, an embolus from the veins crosses to the arterial blood system. This is generally found only with heart problems such as septal defects  (holes in the cardiac septum) between the atria or ventricles. The most common such abnormality is [[patent foramen ovale]], occurring in about 25% of the adult population, but here the defect functions as a valve which is normally closed, because pressure is slightly higher in the left side of the heart. Sometimes, for example if a patient coughs just when an embolus is passing, it might cross to the arterial system.{{citation needed|date=February 2021}}
=== Direction ===
The direction of the embolus can be one of two types:{{citation needed|date=February 2021}}
* Anterograde
* Retrograde
In anterograde embolism, the movement of emboli is in the direction of blood flow. In retrograde embolism, the emboli move in opposition to the blood flow direction; this is usually significant only in blood vessels with low pressure (veins) or with emboli of high weight.{{cn|date=August 2022}}
== Etymology ==
The word ''embolism'' comes from the Greek ἐμβολισμός, meaning "interpressure".{{cn|date=October 2021}}
== See also ==
* [[Embolectomy]]
== References ==
{{Reflist}}
== External links ==
{{Medical resources
| DiseasesDB      = 18165
| ICD10           = {{ICD10|I|74||i|70}}, {{ICD10|I|82||i|80}}, {{ICD10|O|88||o|85}}, {{ICD10|T|79|0|t|79}}-{{ICD10|T|79|1|t|79}}
| ICD9            = {{ICD9|444.9}}
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| MeshID          = D004617
| SNOMED CT       = 414086009
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* [https://web.archive.org/web/20120309144010/http://rad.usuhs.edu/medpix/tf_case.html?pt_id=10480&quiz=no MR of Fat Embolism] Brain Injury from Fat Embolism
{{Vascular diseases}}
{{Pathology of pregnancy, childbirth and the puerperium}}
{{Certain early complications of trauma}}
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[[Category:Hematology]]
[[Category:Diseases of arteries, arterioles and capillaries]]