Embolism
Encyclopedia
In medicine
, an embolism (plural embolisms; from the Greek ἐμβολισμός "insertion") is the event of lodging of an embolus
(a detached intravascular mass capable of clogging arterial capillary beds at a site far from its origin) into a narrow capillary vessel of an arterial bed which causes a blockage (vascular occlusion
) in a distant part of the body.
Embolization
is a procedure that purposely creates such a lodging and occlusion of specific blood vessels with thrombo-emboli in order to deprive tumors (or other pathologic processes) of their perfusion
(blood supply).
. Sometimes, multiple classifications apply; for instance a pulmonary embolism
is classified as an arterial embolism as well, in the sense that 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
.
can cause vessel occlusion in any part of the body. It is a major cause of infarction
(which may also be caused by e.g. arterial compression, rupture or pathological vasoconstriction).
Arterial embolis may be starting in the heart (from a thrombus in the left atrium
secondary to atrial fibrillation
or septic emboli from endocarditis
).
An embolus landing in the brain
from either the heart
or a carotid artery
will likely cause an ischemic stroke
.
Emboli of cardiac origin
are also frequently encountered in clinical practice. Thrombus formation within the atrium in valvular disease occurs mainly in patients with mitral valve
disease, and especially in those with mitral valve
stenosis
with atrial fibrillation
(AF). In the absence of AF, pure mitral regurgitation has low incidence of thromboembolism.
Absolute risk of emboli in idiopathic
AF depends on other risk factors such as increasing age, hypertension
, diabetes, recent heart failure, or previous stroke
.
Thrombus formation can also take place within the ventricle
s, 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 embolization.
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.
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
.
The main complication of arterial embolism is infarction
, that is, tissue death (necrosis
) caused by blockage of the tissue's blood supply.
will always impact in the lungs, after passing through the right side of the heart. This forms a pulmonary embolism
that can be a complication of deep-vein thrombosis. Note that, contrary to popular belief, the most common site of origin of pulmonary emboli are the femoral veins
, not the deep veins of the calf. Deep veins of the calf are the most common site of thrombi, not emboli origin.
The main complication of venous embolism is pulmonary embolism
, that is, blockage of the main artery of the lung
or one of its branches.
, 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. In certain circumstances, e.g. if patient is coughing just when an embolus is passing, passage to the arterial system may occur.
In anterograde embolism, the movement of emboli is in the direction of blood flow. In retrograde embolism, however, 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.
Medicine
Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....
, an embolism (plural embolisms; from the Greek ἐμβολισμός "insertion") is the event of lodging of an embolus
Embolus
An embolus is any detached, itinerant intravascular mass carried by circulation, which is capable of clogging arterial capillary beds at a site distant from its point of origin.By contrast there are non-traveling blockages that develop locally from vascular trauma or...
(a detached intravascular mass capable of clogging arterial capillary beds at a site far from its origin) into a narrow capillary vessel of an arterial bed which causes a blockage (vascular occlusion
Vascular occlusion
Vascular occlusion is a sudden blockage of a blood vessel, usually with a clot. It differs from thrombosis in that it can be used to describe any form of blockage, not just one formed by a clot. When it occurs in a major vein, it can, in some cases, cause deep vein thrombosis. The condition is...
) in a distant part of the body.
Embolization
Embolization
Embolization is a non-surgical, minimally-invasive procedure performed by an interventional radiologist and interventional neuroradiologists. It involves the selective occlusion of blood vessels by purposely introducing emboli.-Therapeutic applications:...
is a procedure that purposely creates such a lodging and occlusion of specific blood vessels with thrombo-emboli in order to deprive tumors (or other pathologic processes) of their perfusion
Perfusion
In physiology, perfusion is the process of nutritive delivery of arterial blood to a capillary bed in the biological tissue. The word is derived from the French verb "perfuser" meaning to "pour over or through."...
(blood supply).
Arterial or venous
Embolism can be classified as whether it enters the circulation in arteries or veins. Arterial embolism are those that follow and, if not dissolved on the way, lodge in a more distal part of the systemic circulationSystemic circulation
Systemic circulation is the part of the cardiovascular system which carries oxygenated blood away from the heart to the body, and returns deoxygenated blood back to the heart. This physiologic theory of circulation was first described by William Harvey...
. Sometimes, multiple classifications apply; for instance a pulmonary embolism
Pulmonary embolism
Pulmonary embolism is a blockage of the main artery of the lung or one of its branches by a substance that has travelled from elsewhere in the body through the bloodstream . Usually this is due to embolism of a thrombus from the deep veins in the legs, a process termed venous thromboembolism...
is classified as an arterial embolism as well, in the sense that the clot follows the pulmonary artery
Pulmonary artery
The pulmonary arteries carry deoxygenated blood from the heart to the lungs. They are the only arteries that carry deoxygenated blood....
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
Deep vein thrombosis
Deep vein thrombosis is the formation of a blood clot in a deep vein. Deep vein thrombosis commonly affects the leg veins or the deep veins of the pelvis. Occasionally the veins of the arm are affected...
.
Arterial
Arterial embolismArterial embolism
Arterial embolism is a sudden interruption of blood flow to an organ or body part due to an embolus adhering to the wall of an artery and blocks the flow of blood, the major type of embolus being a blood clot...
can cause vessel occlusion in any part of the body. It is a major cause of infarction
Infarction
In medicine, infarction refers to tissue death that is caused by a local lack of oxygen due to obstruction of the tissue's blood supply. The resulting lesion is referred to as an infarct.-Causes:...
(which may also be caused by e.g. arterial compression, rupture or pathological vasoconstriction).
Arterial embolis may be starting in the heart (from a thrombus in the left atrium
Left atrium
The left atrium is one of the four chambers in the human heart. It receives oxygenated blood from the pulmonary veins, and pumps it into the left ventricle, via the mitral valve.-Foramen ovale:...
secondary to atrial fibrillation
Atrial fibrillation
Atrial fibrillation is the most common cardiac arrhythmia . It is a common cause of irregular heart beat, identified clinically by taking a pulse. Chaotic electrical activity in the two upper chambers of the heart result in the muscle fibrillating , instead of achieving coordinated contraction...
or septic emboli from endocarditis
Endocarditis
Endocarditis is an inflammation of the inner layer of the heart, the endocardium. It usually involves the heart valves . Other structures that may be involved include the interventricular septum, the chordae tendineae, the mural endocardium, or even on intracardiac devices...
).
An embolus landing in the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
from either the heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
or a carotid artery
Carotid artery
Carotid artery can refer to:* Common carotid artery* External carotid artery* Internal carotid artery...
will likely cause an ischemic stroke
Stroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...
.
Emboli of cardiac origin
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
are also frequently encountered in clinical practice. Thrombus formation within the atrium in valvular disease occurs mainly in patients with mitral valve
Mitral valve
The mitral valve is a dual-flap valve in the heart that lies between the left atrium and the left ventricle...
disease, and especially in those with mitral valve
Mitral valve
The mitral valve is a dual-flap valve in the heart that lies between the left atrium and the left ventricle...
stenosis
Stenosis
A stenosis is an abnormal narrowing in a blood vessel or other tubular organ or structure.It is also sometimes called a stricture ....
with atrial fibrillation
Atrial fibrillation
Atrial fibrillation is the most common cardiac arrhythmia . It is a common cause of irregular heart beat, identified clinically by taking a pulse. Chaotic electrical activity in the two upper chambers of the heart result in the muscle fibrillating , instead of achieving coordinated contraction...
(AF). In the absence of AF, pure mitral regurgitation has low incidence of thromboembolism.
Absolute risk of emboli in idiopathic
Idiopathic
Idiopathic is an adjective used primarily in medicine meaning arising spontaneously or from an obscure or unknown cause. From Greek ἴδιος, idios + πάθος, pathos , it means approximately "a disease of its own kind". It is technically a term from nosology, the classification of disease...
AF depends on other risk factors such as increasing age, hypertension
Hypertension
Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...
, diabetes, recent heart failure, or previous stroke
Stroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...
.
Thrombus formation can also take place within the ventricle
Ventricle (heart)
In the heart, a ventricle is one of two large chambers that collect and expel blood received from an atrium towards the peripheral beds within the body and lungs. The Atria primes the Pump...
s, and it occurs in approximately 30% of anterior-wall myocardial infarction
Myocardial infarction
Myocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...
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
Aneurysm
An aneurysm or aneurism is a localized, blood-filled balloon-like bulge in the wall of a blood vessel. Aneurysms can commonly occur in arteries at the base of the brain and an aortic aneurysm occurs in the main artery carrying blood from the left ventricle of the heart...
s have a 10% risk of embolization.
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.
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
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
and heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
.
The main complication of arterial embolism is infarction
Infarction
In medicine, infarction refers to tissue death that is caused by a local lack of oxygen due to obstruction of the tissue's blood supply. The resulting lesion is referred to as an infarct.-Causes:...
, that is, tissue death (necrosis
Necrosis
Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...
) caused by blockage of the tissue's blood supply.
Venous
Assuming a normal circulation, a thrombus or other embolus formed in a systemic veinVein
In the circulatory system, veins are blood vessels that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart...
will always impact in the lungs, after passing through the right side of the heart. This forms a pulmonary embolism
Pulmonary embolism
Pulmonary embolism is a blockage of the main artery of the lung or one of its branches by a substance that has travelled from elsewhere in the body through the bloodstream . Usually this is due to embolism of a thrombus from the deep veins in the legs, a process termed venous thromboembolism...
that can be a complication of deep-vein thrombosis. Note that, contrary to popular belief, the most common site of origin of pulmonary emboli are the femoral veins
Femoral vein
In the human body, the femoral vein is a blood vessel that accompanies the femoral artery in the femoral sheath. It begins at the adductor canal and is a continuation of the popliteal vein...
, not the deep veins of the calf. Deep veins of the calf are the most common site of thrombi, not emboli origin.
The main complication of venous embolism is pulmonary embolism
Pulmonary embolism
Pulmonary embolism is a blockage of the main artery of the lung or one of its branches by a substance that has travelled from elsewhere in the body through the bloodstream . Usually this is due to embolism of a thrombus from the deep veins in the legs, a process termed venous thromboembolism...
, that is, blockage of the main artery of the lung
Pulmonary artery
The pulmonary arteries carry deoxygenated blood from the heart to the lungs. They are the only arteries that carry deoxygenated blood....
or one of its branches.
Paradoxical (venous to arterial)
In paradoxical embolismParadoxical embolism
A paradoxical embolism is a kind of stroke or other form of arterial thrombosis caused by embolism of a thrombus of venous origin through a lateral opening in the heart, such as a patent foramen ovale....
, 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. In certain circumstances, e.g. if patient is coughing just when an embolus is passing, passage to the arterial system may occur.
Direction
The direction of the embolus can be one of two types:- Anterograde
- Retrograde
In anterograde embolism, the movement of emboli is in the direction of blood flow. In retrograde embolism, however, 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.
External links
- MR of Fat Embolism Brain Injury from Fat Embolism