Tishk International

University Science

Faculty

Medical Analysis Department

Pathology

Fourth Grade- Spring Semester 2020-2021

Dr. Jalal A. Jalal Assistant

Professor of Pathology

Hemodynamic disorders - 3,

Embolism

Contents

Embolism:

Definition

Types

Morphology

Factors that influence the development of

embolism.

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Objectives

1. To define the term “embolism”.

2. To explain it’s pathophysiology.

3. Describe it’s histological changes.

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EMBOLISM

• An embolus is a detached intravascular solid,

liquid, or gaseous mass that is carried by the

blood to a site distant from its point of origin.

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• Virtually 99% of all emboli represent some part

of a dislodged thrombus, hence the term

thromboembolism.

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Rare forms of emboli include

• Fat embolism

• Amniotic fluid emboli

• Air embolism

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• However, unless otherwise specified, an

embolism should be considered to be

thrombotic in origin.

• Inevitably, emboli lodge in vessels too small

to permit further passage, resulting in partial

or complete vascular occlusion.

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• The consequences of thromboembolism include

ischemic necrosis (infarction) of downstream

tissue.

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• Depending on the site of origin, emboli may

lodge anywhere in the vascular tree;

• The clinical outcomes are best understood

from the standpoint of whether emboli lodge in

the pulmonary or systemic circulations.

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Pulmonary Thromboembolism

• Pulmonary embolism has an incidence of 2-4

per 1000 hospitalized patients.

• Although the rate of fatal pulmonary emboli

has declined over the last years,

• pulmonary embolism still causes about

100,000 deaths per year in the United States.

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Pulmonary Thromboembolism ……

• In more than 95% of cases, venous emboli

originate from deep leg vein thrombi.

• They are carried through progressively larger

channels and pass through the right side of the

heart before entering the pulmonary vasculature.

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Pulmonary Thromboembolism ……

• Depending on the size of the embolus, it may

occlude the main pulmonary artery, impact

across the bifurcation (saddle embolus), or pass

out into the smaller, branching arterioles.

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Pulmonary Thromboembolism ……

• Most pulmonary emboli (60% to 80%) are

clinically silent because they are small.

• Sudden death, right heart failure (cor

pulmonale), or cardiovascular collapse

occurs when 60% or more of the pulmonary

circulation is obstructed with emboli.

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• Embolic obstruction of medium-sized arteries

with subsequent vascular rupture can result in

pulmonary hemorrhage but usually does not

cause pulmonary infarction.

• Embolic obstruction of small end-arteriolar

pulmonary branches may result in infarction.

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Microscopical appearance of pulmonary artery embolus

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Systemic Thromboembolism

• Systemic thromboembolism refers to emboli

in the arterial circulation.

• Most (80%) arise from intracardiac mural

thrombi, two-thirds of which are associated

with left ventricular wall infarcts.

• The remainder originate from aortic

aneurysms or thrombi on ulcerated

atherosclerotic plaques.

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• In contrast to venous emboli, which tend to

lodge primarily in one vascular bed (the lung),

• Arterial emboli can travel to a wide variety of

sites;

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The major sites for arteriolar embolization are

1. The lower extremities (75%)

2. The brain (10%),

3. The intestines, kidneys, and spleen affected to

a lesser extent.

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The consequences of embolization in a tissue

depend on:

1. vulnerability to ischemia,

2. caliber of the occluded vessel, and

3. the collateral blood supply;

In general, arterial embolization causes infarction

of the affected tissues.

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Summary

• An embolus is a detached intravascular solid,

liquid, or gaseous mass that is carried by the

blood to a site distant from its point of origin.

• Most emboli represent part of a dislodged

thrombus, so they called thromboemboli.

• consequences of thromboemboli include ischemic

necrosis (infarction) of downstream tissue.

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