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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.
2
Objectives
1. To define the term “embolism”.
2. To explain it’s pathophysiology.
3. Describe it’s histological changes.
3
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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