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1. the occlusion of a blood vessel by an embolus
2. Botany the blocking of a xylem vessel by an air bubble
3. RC Church a prayer inserted in the canon of the Mass between the Lord's Prayer and the breaking of the bread
4. another name (not in technical use) for embolus



disruption of the blood supply to an organ or tissue owing to blockage of a blood vessel by any type of particle transported by the blood or lymph stream but not normally circulating therein.

Circulatory disorders are aggravated by reflex vasospasms and secondary thrombosis. In the case of obstruction of small vessels, blood circulation can be quickly restored by collateral circulation, so that the embolism may be described as incomplete. Thromboembolism, which is caused by a thrombus or part of a thrombus that has broken free, is the type that is most important in practical terms. Emboli from peripheral veins usually lodge in the basin of the pulmonary artery. If there are defects in the septa of the heart, the emboli may reach the arterial system, bypassing the pulmonary circulation; this is called a paradoxical embolism. Embolism in the systemic circulation arteries is usually caused by the breaking away of thrombotic material from the left ventricular valves or walls, as in endocarditis, in heart diseases, and in aneurysm of the left ventricle.

Other possible types are tissue and fat embolisms (especially after extensive and severe injuries or fractures of the long tubular bones), air or gas embolisms (as in the case of open heart surgery, injuries to the large veins of the neck and chest, and decompression sickness), bacillary embolisms (obstruction by aggregations of microbes), and embolisms caused by foreign bodies—mainly by small fragments in gunshot wounds—which are sometimes moved by the force of gravity against the direction of the blood stream (retrograde, or venous, embolism).

Treatment includes the use of anticoagulants, thrombolytic and spasmolytic agents, antibiotics, therapeutic recompression (for decompression sickness), and surgical removal of the embolus (embolectomy).


Chazov, E. I. Trombozy i embolii v klinike vnutrennikh boleznei. Moscow-Warsaw, 1966.
Tregubenko, A. I. Trombozy i embolii v khirurgii. Kiev, 1972.
Perlick, E. Antikoagulanten. Leipzig, 1964.



The blocking of a blood vessel by an embolus.
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Percutaneous transcatheter closure of patent foramen ovale in patients with paradoxical embolism.
The authors suggested that the association of PFO with ASA has a higher risk of paradoxical embolism.
CLOSURE I is designed to evaluate the effectiveness of NMT's STARFlex[R] implant technology in preventing recurrent stroke and/or TIA due to a presumed, paradoxical embolism through a PFO.
Common cardiac causes of systemic embolism are ventricular mural thrombus, LAA thrombus secondary to valvular pathology or chronic atrial fibrillation, prosthetic valves or calcified leaflets, cardiac tumors, infective endocarditis, paradoxical embolism through an atrial septal defect or patent foramen ovale (1).
Findings from several studies suggest that the mechanism by which sleep-disordered breathing increases stroke risk is by "leading to or worsening hypertension and heart disease and possibly by causing reductions in cerebral blood flow, altered cerebral autoregulation, impaired endothelial function, accelerated atherogenesis, hypercoagulability, inflammation, and paradoxical embolism in patients with patent foramen ovale," the guideline states.
The larger malformations are associated with arterial hypoxaemia, transient ischaemic attacks, and stroke secondary to paradoxical embolism and cerebral abscess.
It must be stressed, however, that a Valsalva manoeuvre is ill-advised in the event of venous air embolism--because of the risk, on its release, of paradoxical embolism (1,4).