Embolism: is the process of impaction of an embolus in a vessel wall too small to permit its further passage, resulting in partial or complete occlusion.

Embolism

Definition

Embolism: is the process of impaction of an embolus in a vessel wall too small to permit its further passage, resulting in partial or complete occlusion of the vessel.

Embolus: is a detached intravascular solid, liquid or gaseous mass, carried by the blood to a site distant from its point of origin.

Types of emboli

1-Detached thrombi (99% of all emboli).2-Air emboli.3-Amniotic fluid emboli.4-Fat emboli.5-Tumour emboli (in malignant tumours).6-Miscellaneous emboli such as:

foreign body emboli (bullet) parasitic emboli (worms or ova) red cell aggregates especially in infection.

Detached thrombi (thromboembolism).These emboli may be septic or aseptic.

Thromboemboli are classified according to whether they lodge in the pulmonary or systemic circulation:

Pulmonary thromboembolism Systemic thromboembolism

In more than 95% of cases, venous emboli originate from deep leg vein thrombi above the level of the knee

They are carried through larger channels and usually pass through the right side of the heart into the pulmonary vasculature.

Depending on the size of the embolus, it may :

occlude the main pulmonary artery, impact across the bifurcation (saddle

embolus) pass out into the smaller, branching

arterioles.

The effects of pulmonary embolism depend on:

• the size of these emboli• the presence or absence of pulmonary

congestion at the time of impaction

Large embolus occluding the main pulmonary artery or its main branches may cause sudden death or acute heart failure.

Embolic obstruction of medium-sized arteries may result in pulmonary hemorrhage but usually does not cause pulmonary infarction because of the dual blood flow into the area from the bronchial circulation

• Multiple minute emboli will reach the more peripheral branches of the pulmonary circulation passes unnoticed or silent.

• Repeated showers of small emboli, over time, become organized and incorporated in the vessel walls leading to narrowing of the vascular lumina pulmonary hypertension with subsequent right heart failure (Cor Pulmonale)

Right Ventricle Embolus from Leg Vein

Pulmonary Embolus

Embolization (Embolus)Thromboembolism of Pulmonary Artery

Saddle embolus

Systemic thromboembolism

It refers to emboli that travel through the arterial circulation.

These emboli originate in the left heart, aorta, or large arteries and are carried by the arterial blood into various organs such as brain, spleen, and kidney.

Example

Mural thrombi in the left ventricle. Infective vegetations on the mitral and aortic valves.

Left atrial thrombi.Thrombus on the atheromatous lesions of the aorta. Paradoxical emboli: are venous emboli that reach the arterial circulation by crossing right to left heart through interatrial or interventricular septal defect. So in this condition, the detached thrombi bypass the lung and reach directly to the systemic circulation.

Effects of arterial thromboemboli

1- Lodgment in end arteries or arteries with deficient collaterals leads to infarct.

The major sites of impaction of arterial emboli are : the lower extremities (70-75% of cases), brain (10% of cases), viscera (10% of cases)

2-Septic emboli resulting from infected thrombi e.g., vegetations of bacterial endocarditis, cause pyamic abscess.

Air embolism

Air or gas may gain access to the circulation:

During delivery or abortion, Injury to the lung or chest wall, Injury to a large neck vein, During blood or fluid infusion.

100 c.c. of air are required to produce problems, usually they lodge into a major vessel in the lung leading to sudden death or acute heart failure

Caisson's disease or decompression sickness

Occurs in persons exposed to sudden changes in atmospheric pressure.

This occurs during deep diving when the gas is breathed under high pressure, increased amount dissolves in the blood, tissue fluids and fat.

Gas emboli may induce focal ischemia in a number of tissues, including brain and heart

Air embolism.Scuba diving.Death. Cerebellum. Air bubbles inside the

cortical cerebellum vessels .

Heart. Air embolism. Scuba diving. Death.

Amniotic fluid embolism or infusion

It is a rare complication of labour or immediate post partum period. It is due to tear in the placental membranes and rupture of uterine and/or cervical veins, followed by entry of the amniotic fluid with all its contents into the maternal circulation.

The condition ends in fatal pulmonary embolism to the mother

This section of lung is from a woman who died in shock shortly after delivery. Within the vessels are squames

from the fetus which were present in amniotic fluid .

Fat embolism

Minute globules of fat can be demonstrated in the circulation following closed fractures of the shafts of long bones, and rarely, with soft tissue trauma, and burns.

The fat globules gain access to the circulation through ruptured veins, these fat globules produce pulmonary or systemic embolism

bone marrow embolus from patient shows viable marrow fragments in a

medium-sized artery.

Bone Marrow EmbolusIn Pulmonary Vessel