WordNet

an abnormal particle (e.g. an air bubble or part of a clot) circulating in the blood
of or relating to an embolism or embolus

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/04/10 17:29:17」(JST)

wiki en

An embolus (plural emboli; from the Greek ἔμβολος "clot, lit. ram") is any detached, traveling intravascular mass (solid, liquid, or gaseous) carried by circulation, which is capable of clogging arterial capillary beds (create an arterial occlusion) at a site distant from its point of origin.^[1]

Illustration depicting embolism from detached thrombus

By contrast there are non-traveling blockages that develop locally from vascular trauma or epithelial pathology and vascular inflammation — like atheroma, thrombi. However, if a thrombus breaks loose from its genesis site it becomes a thrombo-embolus and if not broken down during transit, may cause embolism(s).^[2]

The term was coined in 1848 by Rudolf Virchow.^[3]

Classification by substance

Thromboembolism – embolism of thrombus (blood clot).
Cholesterol embolism – embolism of cholesterol, often from atherosclerotic plaque inside a vessel.
Fat embolism – embolism of bone fracture or fat droplets.
Air embolism (also known as a gas embolism) – embolism of air bubbles.
Septic embolism – embolism of bacteria-containing pus.
Tissue embolism – embolism of small fragments of tissue.
Foreign body embolism – embolism of foreign materials such as talc and other small objects.
Amniotic fluid embolism – embolism of amniotic fluid, foetal cells, hair, or other debris that enters the mother's bloodstream via the placental bed of the uterus and triggers an allergic reaction.

In thromboembolism, the thrombus (blood clot) from a blood vessel is completely or partially detached from the site of thrombosis (clot). The blood flow will then carry the embolus (via blood vessels) to various parts of the body where it can block the lumen (vessel cavity) and cause vessel obstruction or occlusion. Note that the free-moving thrombus is called an embolus.^[4] A thrombus is always attached to the vessel wall and is never freely moving in the blood circulation. This is also the key difference for pathologists to determine the cause of a blood clot, either by thrombosis or by post-mortem blood clot. Vessel obstruction will then lead to different pathological issues such as blood stasis and ischemia. However, not only thromboembolism will cause the obstruction of blood flow in vessels, but also any kind of embolism is capable of causing the same problem.

Fat embolism usually occurs when endogenous (from sources within the organism) fat tissue escapes into the blood circulation. The usual cause of fat embolism is therefore the fracture of tubular bones (such as the femur), which will lead to the leakage of fat tissue within the bone marrow into ruptured vessels. There are also exogenous (from sources of external origin) causes such as intravenous injection of emulsions.

An air embolism, on the other hand, is usually always caused by exogenic factors. This can be the rupture of alveoli, and inhaled air can be leaked into the blood vessels. Other more-common causes include the puncture of the subclavian vein by accident or during operation where there is negative pressure. Air is then sucked into the veins by the negative pressure caused by thoracic expansion during the inhalation phase of respiration. Air embolism can also happen during intravenous therapy, when air is leaked into the system (however this iatrogenic error in modern medicine is extremely rare).

Gas embolism is a common concern for deep-sea divers because the gases in our blood (usually nitrogen and helium) can be easily dissolved at higher amounts during the descent into deep sea. However, when the diver ascends to the normal atmospheric pressure, the gases become insoluble, causing the formation of small bubbles in the blood. This is also known as decompression sickness or the Bends. This phenomenon is explained by Henry's Law in physical chemistry.

Embolism by other materials are rather rare. Septic embolism happens when a purulent tissue (pus-containing tissue) is dislodged from its original focus. Tissue embolism is a near-equivalent to cancer metastasis, which happens when cancer tissue infiltrates blood vessels, and small fragments of them are released into the blood stream. Foreign-body embolism happens when exogenous—and only exogenous—materials such as talc enter the blood stream and cause occlusion or obstruction of blood circulation. Amniotic-fluid embolism is a rare complication of childbirth.

References

^ Kumar V., Abbas A.K., Fausto N. Pathologic Basis of Disease.
^ http://www.medterms.com/script/main/art.asp?articlekey=3224
^ Hellemans, Alexander; Bryan Bunch (1988). The Timetables of Science. New York, New York: Simon and Schuster. p. 317. ISBN 0-671-62130-0. Cite uses deprecated parameters (help)
^ Howland, Richard D.; Mycek, Mary J. Pharmacology. Lippincott's illustrated reviews (3rd ed.). Philadelphia : Lippincott Williams & Wilkins, c2006. p. 227. ISBN 0-7817-4118-1.

UpToDate Contents

全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.

1. 成人における急性肺塞栓症の概要 overview of acute pulmonary embolism in adults
2. 下肢の急性動脈閉塞（急性下肢虚血）の概要 overview of acute arterial occlusion of the extremities acute limb ischemia
3. 心臓内および大動脈内の全身性塞栓源の検出における心エコー echocardiography in detection of cardiac and aortic sources of systemic embolism
4. Acute mesenteric arterial occlusion
5. 静脈血栓塞栓症の患者における理論的根拠と無期限の抗凝固の適応 rationale and indications for indefinite anticoagulation in patients with venous thromboembolism

English Journal

Diffusion-weighted lesions in acute ischaemic stroke patients with migraine.

Oygarden H1, Kvistad CE, Bjørk M, Thomassen L, Waje-Andreassen U, Naess H.Author information 1Department of Neurology, Haukeland University Hospital, Bergen, Norway; Institute of Clinical Medicine, University of Bergen, Bergen, Norway.AbstractOBJECTIVES: There is increasing knowledge about an association between migraine and ischaemic stroke. Cortical spreading depression (CSD) is the probable biological substrate of migrainous aura. To investigate the influence of CSD on the apparent stroke - migraine association, we hypothesized that magnetic resonance (MR) diffusion weighted images of acute ischaemic stroke patients would reveal an association between small cortical infarctions and migraine.
Acta neurologica Scandinavica. Supplementum.Acta Neurol Scand Suppl.2014 Apr;(198):41-6. doi: 10.1111/ane.12236.
OBJECTIVES: There is increasing knowledge about an association between migraine and ischaemic stroke. Cortical spreading depression (CSD) is the probable biological substrate of migrainous aura. To investigate the influence of CSD on the apparent stroke - migraine association, we hypothesized that m
PMID 24588506

Detection of cardiac myxomas with non-contrast chest CT.

Shin W1, Choe YH, Kim SM, Song IY, Kim SS.Author information 1Department of Radiology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.AbstractBACKGROUND: Cardiac myxomas are sources of systemic embolism. Currently a large volume of chest CT and calcium-scoring CT scans are performed without contrast injection.
Acta radiologica (Stockholm, Sweden : 1987).Acta Radiol.2014 Apr 1;55(3):273-8. doi: 10.1177/0284185113496561. Epub 2013 Aug 7.
BACKGROUND: Cardiac myxomas are sources of systemic embolism. Currently a large volume of chest CT and calcium-scoring CT scans are performed without contrast injection.PURPOSE: To evaluate the diagnostic capability of non-contrast CT covering heart in detecting cardiac myxomas.MATERIAL AND METHODS:
PMID 23926237

Economic evaluation of using a genetic test to direct breast cancer chemoprevention in white women with a previous breast biopsy.

Green LE1, Dinh TA, Hinds DA, Walser BL, Allman R.Author information 1Department of Mathematics, University of North Carolina at Chapel Hill, CB#3250, Chapel Hill, NC, 27599, USA, linda.green@unc.edu.AbstractBACKGROUND: Tamoxifen therapy reduces the risk of breast cancer but increases the risk of serious adverse events including endometrial cancer and thromboembolic events.
Applied health economics and health policy.Appl Health Econ Health Policy.2014 Apr;12(2):203-17. doi: 10.1007/s40258-014-0089-6.
BACKGROUND: Tamoxifen therapy reduces the risk of breast cancer but increases the risk of serious adverse events including endometrial cancer and thromboembolic events.OBJECTIVES: The cost effectiveness of using a commercially available breast cancer risk assessment test (BREVAGen™) to inform the
PMID 24595521