Embolism

Slide 1 · Embolism: pathologic transport and vascular injury

A detached intravascular mass travels to an anatomically distant vascular bed.

Most emboli are thrombotic fragments, but solid, liquid, and gaseous emboli also occur.

Clinical injury reflects the destination, vessel caliber, and remaining perfusion.

Source

Transport

Occlusion

Tissue effect

Schematic: source → transport → vascular lodging → downstream injury.

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · Learning objectives

By the end, distinguish routes, compositions, and consequences of embolization.

Explain the difference between thrombosis, embolization, and infarction.

Trace venous, systemic arterial, and paradoxical embolic routes.

Connect embolus type to its pathogenesis, pathology, and clinical presentation.

Interpret focused clinicopathologic scenarios.

Mechanism

Vascular destination

Morphology

Clinical consequence

Slide 3 · An embolus is defined by displacement

The defining event is transport away from the original location.

The embolic material is intravascular before transport.

Blood flow carries it from origin to a remote vessel.

Arrest usually occurs where the vascular lumen becomes too narrow.

Downstream consequences range from none to infarction.

Detachment

Blood-borne transport

Lodging

Distal injury

Slide 4 · Thrombus versus embolus

Local formation and distal transport are different events.

Feature

Thrombus

Embolus

Defining process

Forms locally

Travels from origin

Location

At formation site

Distant site of lodging

Relationship

Can embolize

May be thrombotic or not

Feature

Thrombus

Embolus

Slide 5 · Three physical states can embolize

The definition accommodates material beyond coagulated blood.

Solid: Thrombi, plaque debris, tumor fragments, marrow, foreign bodies.

Liquid: Fat droplets and amniotic fluid.

Gas: Air entry or nitrogen coming out of solution.

Embolic process

Solid

Liquid

Gas

Slide 6 · Composition is not the same as destination

Two independent classification axes organize embolic disease.

Composition

Example

Potential destination

Solid

Venous thrombus

Pulmonary artery

Solid

Cardiac mural thrombus

Systemic artery

Liquid

Marrow fat droplets

Pulmonary microvessels

Gas

Nitrogen bubbles

Blood and tissues

Composition

Example

Potential destination

Slide 7 · Embolic material follows the blood stream

Flow anatomy determines the likely point of arrest.

A fragment enters progressively larger upstream channels after detachment.

Beyond the heart, it encounters successively smaller arterial branches.

It lodges when size and geometry prevent further passage.

Detaches

Larger conduit

Arterial branching

Lodges

Slide 8 · Partial and severe vascular obstruction

An embolus may restrict rather than entirely abolish perfusion.

Partial obstruction reduces cross-sectional area available for flow.

A completely blocked channel cannot conduct flow; Parallel supply may persist.

Organ function depends on the territory and reserve circulation.

Partial obstruction

Blood flow →

Near-complete obstruction

Blood flow →

Schematic longitudinal vessel views (not histology).

Slide 9 · Four determinants of embolic damage

The same material can have very different clinical consequences.

Size of the embolus relative to the recipient vessel.

Location within the vascular tree and downstream tissue served.

Available collateral or dual blood supply.

Intrinsic susceptibility of the target tissue to ischemia.

Embolus size

Location

Collateral supply

Tissue vulnerability

Slide 10 · Major routes of thromboembolism

Venous and arterial emboli enter different circulatory circuits.

Systemic venous thrombus → right heart → pulmonary arteries.

Left-sided cardiac or aortic thrombus → systemic arterial branches.

Rare right-to-left shunt permits paradoxical systemic embolization.

Venous DVT

Right heart

Lungs

Left-heart clot

Aorta

Organs

Venous clot

R→L shunt

Organs

Slide 11 · Thromboemboli predominate

Detachment of pre-existing thrombi accounts for most embolic events.

The parent thrombus remains attached locally until a fragment dislodges.

A propagating portion may be poorly attached and prone to fragment.

Embolization is one of four recognized thrombus fates.

Local thrombus

Fragment detaches

Circulating fragment

Lodged embolus

Slide 12 · Fates of an established thrombus

Embolization competes with growth, lysis, and organization.

Propagation adds platelets and fibrin to the original thrombus.

Dissolution results from fibrinolysis, particularly in recent thrombi.

Organization and recanalization develop as tissue grows into older thrombi.

Embolization carries detached fragments downstream.

Embolic process

Propagation

Dissolution

Organization

Embolization

Slide 13 · Deep venous thrombosis is the main PE source

Lower-extremity deep venous thrombi are the classic precursors of pulmonary emboli.

Proximal leg veins are clinically important sources.

Stasis and hypercoagulability are frequent contributors to leg DVT.

Venous thrombi may be clinically silent until embolization.

Leg deep veins

IVC

Right heart

Pulmonary artery

Slide 14 · Why venous thrombi embolize

Thrombus architecture helps explain fragmentation.

Venous thrombi form in low-flow settings and may extend as long luminal casts.

Attachment is often most secure at the point of initiation.

The expanding tail may fragment and enter venous return.

Flow toward heart →

Attached point of origin

Propagating portion: More prone to detach

Native editable schematic of venous thrombus propagation; Not a specimen.

Slide 15 · A silent DVT can have a major consequence

Absence of local symptoms does not exclude an embolic source.

Collateral venous drainage may blunt pain and edema.

Embolization can be the first clinically recognized manifestation.

Source assessment therefore extends beyond the symptomatic organ.

Venous obstruction

Collateral channels

Few leg symptoms

Pulmonary embolus

Slide 16 · The anatomic route to the pulmonary arteries

Venous fragments traverse the right-sided cardiac circulation.

Lower-extremity vein → inferior vena cava.

Right atrium → right ventricle.

Pulmonary trunk → right or left pulmonary arterial branches.

DVT

IVC / right atrium

Right ventricle

Pulmonary arteries

Slide 17 · Pulmonary emboli lodge at branching points

Large emboli may obstruct central pulmonary arterial segments.

Central occlusion may involve the main pulmonary trunk.

A saddle embolus straddles the bifurcation of the pulmonary trunk.

Smaller fragments reach segmental and distal branches.

Trunk

Schematic central embolus; Not a gross specimen or angiographic image.

Slide 18 · Saddle pulmonary embolism: Morphology

“Saddle” describes anatomic position, not a separate embolus composition.

The embolus bridges the major pulmonary arterial bifurcation.

It may compromise flow into both lungs.

Severity still depends on total obstruction and hemodynamic response.

Main pulmonary artery

Schematic central embolus; Not a gross specimen or angiographic image.

Slide 19 · Single versus multiple pulmonary emboli

Embolic burden can accumulate through repeated events.

One large fragment can obstruct a proximal vessel.

A shower of smaller emboli can lodge in multiple distal vessels.

Sequential events help explain recurrence and chronic vascular consequences.

Embolic process

Large central embolus

Multiple distal emboli

Recurrent episodes

Slide 20 · Small pulmonary emboli may be silent

Small emboli can resolve without a clinically apparent episode.

The Robbins text describes many small PE as clinically silent.

Organization may incorporate the thromboembolus into the vessel wall.

Residual thin fibrous webs may persist after organization.

Small embolus

Organization

Incorporation

Fibrous web

Slide 21 · Why PE does not always cause lung infarction

The lung has two arterial systems with partially overlapping perfusion.

Pulmonary arteries provide the low-pressure gas-exchange circulation.

Bronchial arteries provide a systemic arterial contribution.

Preserved bronchial circulation can prevent tissue necrosis after PE.

Pulmonary artery

Bronchial artery

Lung tissue perfusion

Alternative bronchial flow can help preserve viability

Slide 22 · Pulmonary hemorrhage is not synonymous with infarction

Vascular rupture may allow blood into tissue without irreversible ischemic necrosis.

Finding

Hemorrhage

Infarction

Mechanism

Blood extravasation

Ischemic necrosis

Necrosis required?

No

Yes

PE setting

Possible with viable tissue

Requires insufficient perfusion

Finding

Hemorrhage

Infarction

Slide 23 · When pulmonary infarction becomes more likely

Dual circulation is protective but not absolute.

Distal small-branch occlusions may produce hemorrhage or infarction.

Compromised bronchial perfusion reduces protection.

The involved territory and collateral reserve determine the outcome.

Pulmonary branch occlusion

Impaired alternative flow

Ischemia

Hemorrhagic infarct

Slide 24 · Massive PE produces acute right-heart stress

A large obstructed vascular bed abruptly increases pulmonary vascular resistance.

The right ventricle faces an acute increase in afterload.

Right ventricular failure can limit left ventricular filling.

Severe episodes may cause cardiovascular collapse or sudden death.

Large PE burden

Pulmonary resistance ↑

Acute RV failure

Systemic collapse

Slide 25 · Pulmonary vascular obstruction and shock

Mechanical occlusion has systemic hemodynamic effects.

Reduced pulmonary flow limits delivery to the left heart.

Acute RV dilation and dysfunction can aggravate low cardiac output.

Death may occur without a pulmonary infarct.

Pulmonary obstruction

RV overload

Low forward output

Shock

Slide 26 · Recurrent emboli can produce chronic strain

Embolization is not limited to isolated acute events.

Multiple emboli over time may increase pulmonary vascular resistance.

Persistent obstruction and organization can contribute to pulmonary hypertension.

Prolonged pressure burden can culminate in right ventricular failure.

Recurrent emboli

Residual obstruction

Pulmonary hypertension

RV failure

Slide 27 · Paradoxical embolism crosses circulatory circuits

A venous embolus rarely reaches the systemic arterial circulation.

An interatrial or interventricular defect can provide a conduit.

Right-to-left passage bypasses the pulmonary arterial filter.

The embolus then threatens a systemic organ.

Venous DVT

Right heart

Lungs

Left-heart clot

Aorta

Organs

Venous clot

R→L shunt

Organs

Slide 28 · Paradoxical embolism: Causal sequence

Both a venous source and an appropriate intracardiac route are required.

A thrombus detaches into systemic venous blood.

The embolus traverses a right-to-left intracardiac communication.

It enters left-sided outflow and reaches an arterial organ bed.

Venous source

Right-to-left passage

Aorta

Systemic organ

Slide 29 · Systemic emboli usually arise in the left heart

The left ventricle and atrium are frequent origins of arterial thromboemboli.

Left ventricular mural thrombus can follow myocardial infarction.

Atrial enlargement and fibrillation favor atrial mural thrombus.

Detached material enters the aorta and systemic arteries.

Cardiac mural thrombus

Left ventricle / atrium

Aorta

Systemic arteries

Slide 30 · Cardiac mural thrombi: Why they form

Abnormal flow and damaged endocardial surfaces promote local thrombosis.

Postinfarction dyskinesia or akinesia creates abnormal ventricular flow.

Atrial fibrillation reduces effective atrial emptying.

Embolization converts a cardiac source into distant organ ischemia.

Wall injury

Abnormal contraction

Blood stasis

Distal embolism

Slide 31 · Aortic and valvular sources of systemic emboli

Not all systemic arterial emboli originate in the ventricular cavity.

Aortic aneurysms can harbor emboligenic thrombi.

Atherosclerotic plaques can release debris or associated thrombus.

Valvular vegetations can break off and enter the systemic circulation.

Embolic process

Aortic aneurysm

Atherosclerotic plaque

Valve vegetation

Slide 32 · Septic emboli add an infectious mechanism

Infected valvular vegetations can spread microbes with the embolic fragment.

An embolus may occlude a vessel and seed bacteria or fungi.

Infection can intensify tissue destruction beyond ischemia alone.

This differs from sterile mural-thrombus embolization.

Infected vegetation

Fragmentation

Septic embolus

Infected infarct

Slide 33 · Arterial destinations depend on blood flow

Systemic emboli reach organs according to source anatomy and downstream flow.

The lower extremities and brain are common destinations.

Kidneys, spleen, intestines, and upper extremities are also vulnerable.

Distribution is not determined by embolus composition alone.

Embolic process

Lower limbs

Brain

Kidney / spleen

Bowel

Slide 34 · Why an arterial embolus causes infarction

Acute reduction in flow may outpace local collateral compensation.

End-arterial organs are especially vulnerable to acute obstruction.

Small arterial occlusions may be tolerated where collaterals are adequate.

Tissue-specific ischemic sensitivity determines the injury threshold.

Arterial occlusion

Inadequate collateral flow

Ischemia

Infarction

Slide 35 · Contrast: Renal versus pulmonary embolic injury

Perfusion architecture helps explain differences in tissue outcome.

Feature

Kidney

Lung

Dominant architecture

End-arterial

Dual arterial supply

Typical embolic threat

Renal infarction

PE with variable tissue necrosis

Alternative perfusion

Limited

Bronchial circulation

Feature

Kidney

Lung

Slide 36 · Cholesterol and atheromatous debris can embolize

Not every solid arterial embolus resembles a fibrin-rich thrombus.

Plaque material can detach from diseased large arteries.

Cholesterol-rich debris can obstruct small downstream vessels.

Recognition requires linking vascular source to microvascular injury.

Atheromatous plaque

Debris detaches

Arterial transport

Small-vessel lodging

Slide 37 · Rare solid emboli broaden the differential

Pathologic transport can involve malignant tissue, marrow, or foreign matter.

Tumor fragments are an example of nonthrombotic solid emboli.

Marrow fragments may accompany fat embolization after skeletal trauma.

Foreign-body emboli arise from intravascular introduction of material.

Embolic process

Tumor fragments

Bone marrow

Foreign bodies

Slide 38 · Fat embolism follows major skeletal injury

Marrow fat can enter injured small venules and reach the circulation.

Long-bone fractures and severe skeletal trauma are classic settings.

Traumatic rupture of marrow vascular channels permits entry.

Some cases follow burns or soft-tissue trauma.

Bone injury

Marrow sinusoidal disruption

Fat enters blood

Pulmonary microvessels

Slide 39 · Fat embolism is not fat embolism syndrome

Microscopic fat emboli are more frequent than the symptomatic syndrome.

Term

Fat embolism

Fat embolism syndrome

Core definition

Fat in vessels

Systemic clinical illness

Symptoms required

No

Yes

Clinical focus

Distribution

Pulmonary + neurologic signs

Term

Fat embolism

Fat embolism syndrome

Slide 40 · Fat droplets reach the lung from marrow

Marrow fragments and fat globules travel through the venous circuit.

Skeletal trauma creates access to venous blood.

Microemboli lodge in pulmonary microcirculation.

Systemic manifestations also implicate the cerebral circulation.

Fractured long bone

Venous circulation

Pulmonary microvasculature

Organ dysfunction

Slide 41 · The clinical delay is diagnostically useful

Fat embolism syndrome often manifests after an interval following injury.

Onset typically 1–3 days after injury.

Early features include tachypnea, dyspnea, and tachycardia.

Neurologic irritability or restlessness may progress to coma.

Trauma

Latent interval

Respiratory signs

Neurologic signs

Slide 42 · Fat embolism syndrome: Characteristic cluster

Pulmonary, neurologic, and hematologic abnormalities reflect diffuse microvascular injury.

Respiratory insufficiency or hypoxemia.

Neurologic dysfunction, from restlessness to delirium or coma.

Thrombocytopenia and anemia.

Petechial rash may provide an additional diagnostic clue.

Respiratory

Neurologic

Hematologic

Petechiae

Slide 43 · FES injury is mechanical and biochemical

Vessel blockage alone does not account for its systemic effects.

Fat droplets plus cellular aggregates occlude small vessels.

Free fatty acids exert endothelial toxicity.

Activated platelets and recruited granulocytes amplify injury.

Fat microemboli

Endothelial injury

Inflammatory activation

Capillary dysfunction

Slide 44 · Fat-associated platelet changes

Hematologic findings emerge from circulating cell interactions.

Platelets adhere to fat globules and may aggregate or be sequestered.

Anemia may follow red-cell aggregation or hemolysis.

Petechiae are associated with acute thrombocytopenia.

Fat globules

Platelet adhesion

Thrombocytopenia

Petechial rash

Slide 45 · Histologic pitfall: Routine processing removes fat

A negative-appearing fat space is not an intrinsically stained droplet.

Technique

Paraffin H&E

Frozen-section fat stain

Effect on lipid

Usually extracted

Can preserve lipid

Finding

Empty spaces / marrow cells

Fat-positive globules

Interpretive caution

Not definitive alone

Requires context

Technique

Paraffin H&E

Frozen-section fat stain

Slide 46 · Fat embolism versus thrombotic PE

Both may impair pulmonary circulation but have different pathogenesis.

Dimension

Thrombotic PE

Fat embolism syndrome

Source

Deep venous thrombus

Bone / soft-tissue injury

Vessels

Central to peripheral pulmonary

Predominantly microvascular

Distinctive effects

RV overload or infarction

Neurologic / petechial / cytopenic

Dimension

Thrombotic PE

Fat embolism syndrome

Slide 47 · Air embolism requires gas to enter circulation

An air–blood interface and favorable pressure gradient can enable entry.

Air entry occurs when a vessel communicates with outside air.

Pressure gradients influence whether gas is aspirated into vessels.

Intravascular bubbles may obstruct flow and trigger inflammation.

Open vascular conduit

Air entry

Bubble coalescence

Downstream ischemia

Slide 48 · Clinical settings of iatrogenic air entry

Procedures can inadvertently create access for ambient gas.

Endovascular and other interventional procedures.

Certain neurosurgical positions and procedures.

Mechanical ventilation, obstetric or laparoscopic interventions.

Chest wall injury may also allow air entry.

Embolic process

Vascular procedures

Neurosurgery

Ventilation

Trauma / obstetrics

Slide 49 · Gas bubbles cause more than simple plugging

Mechanical obstruction is amplified by host responses.

Bubbles coalesce and reduce flow in receiving vessels.

Inflammatory responses may injure pulmonary alveoli.

Gas bubbles reaching the CNS can cause acute neurologic dysfunction.

Circulating bubbles

Microvascular obstruction

Inflammation

Organ injury

Slide 50 · Decompression sickness: A distinct gas source

Dissolved nitrogen can form bubbles after abrupt pressure reduction.

High ambient pressure increases dissolved nitrogen in blood and tissues.

Rapid ascent lowers pressure before nitrogen can be eliminated.

Gas leaves solution and expands into bubbles.

High ambient pressure

Dissolved nitrogen

Rapid decompression

Bubble formation

Slide 51 · Nitrogen comes out of solution during rapid ascent

The critical issue is the kinetics of pressure reduction.

With gradual ascent, gas can be eliminated over time.

With rapid ascent, tissue nitrogen becomes supersaturated.

Bubbles can form in vessels and supporting tissues.

Deep exposure

Nitrogen dissolved

Rapid ascent

Tissue + vessel bubbles

Slide 52 · The bends and the chokes

Symptoms reflect where the gas bubbles accumulate.

Syndrome

Bends

Chokes

Principal site

Joints / supporting tissue

Pulmonary vasculature

Typical effect

Severe pain

Respiratory distress

Shared mechanism

Decompression bubbles

Decompression bubbles

Syndrome

Bends

Chokes

Slide 53 · Caisson disease: Chronic skeletal injury

Persistent gas emboli may produce repeated ischemic bone damage.

A chronic form of decompression disease affects the skeletal system.

Ischemic necrosis can occur in femoral heads, tibiae, and humeri.

This differs from an acute isolated episode of the bends.

Persistent gas emboli

Osseous ischemia

Focal necrosis

Chronic skeletal disease

Slide 54 · Why controlled recompression works

The treatment principle reverses bubble formation rather than removing a solid embolus.

Increased pressure drives gas bubbles toward dissolution.

Slow subsequent decompression enables gradual gas elimination.

Rapid decompression again risks recurrent bubble formation.

Recompression

Bubbles redissolve

Controlled decompression

Gas elimination

Slide 55 · Air entry versus decompression gas embolism

Both generate bubbles, but the gas enters by different routes.

Feature

Air entry

Decompression sickness

Gas source

Outside atmosphere

Dissolved tissue nitrogen

Trigger

Vascular–air conduit

Rapid pressure reduction

Typical clue

Procedure / trauma

Rapid ascent

Feature

Air entry

Decompression sickness

Slide 56 · Amniotic fluid embolism is an obstetric emergency

It usually occurs during labor or in the immediate postpartum period.

Amniotic contents gain access to the maternal circulation.

The ensuing syndrome involves pulmonary, hemodynamic, and coagulation abnormalities.

Mechanisms include immune and mediator responses, not only physical blockage.

Labor / delivery

Maternal entry of fluid

Mediator activation

Cardiopulmonary collapse

Slide 57 · How fetal material reaches maternal blood

Placental membrane tears or uterine venous disruption can create an entry route.

Amniotic fluid and fetal tissue enter the maternal vascular compartment.

Pulmonary microvasculature may contain fetal-origin components.

Their presence supports mechanism but does not reduce the syndrome to plugging alone.

Membrane / vein disruption

Fluid enters maternal blood

Pulmonary exposure

Systemic response

Slide 58 · Amniotic fluid triggers mediator-driven injury

Circulatory compromise is disproportionate to simple embolic obstruction.

Amniotic material contains tissue factor and activated coagulation factors.

Coagulation and innate immune activation release vasoactive mediators.

Pulmonary hypertension and RV dysfunction can rapidly develop.

Amniotic material

Coagulation + innate immunity

Vasoactive mediators

Pulmonary hypertension

Slide 59 · From maternal pulmonary hypertension to edema

Right- and left-sided dysfunction may occur in sequence.

A sudden increase in pulmonary vascular resistance stresses the right ventricle.

Hypoxia and left-heart dysfunction may follow.

Pulmonary edema and diffuse alveolar damage contribute to respiratory failure.

Pulmonary vasoconstriction

RV failure + hypoxia

LV impairment

Edema / alveolar damage

Slide 60 · The clinical pattern includes DIC

Coagulopathy distinguishes amniotic fluid embolism from many ordinary thrombotic PE cases.

Abrupt dyspnea, cyanosis, and shock are early manifestations.

Neurologic impairment may range from headache to seizures or coma.

Disseminated intravascular coagulation may rapidly emerge.

Abrupt respiratory crisis

Shock

Neurologic changes

DIC

Slide 61 · Fetal components in pulmonary vessels

Autopsy findings can support exposure to amniotic constituents.

Squamous cells shed from fetal skin.

Lanugo hair and fat derived from vernix caseosa.

Mucin derived from fetal respiratory or gastrointestinal tract.

Interpret tissue findings with the characteristic clinical syndrome.

Embolic process

Squamous cells

Lanugo hair

Vernix fat

Mucin

Slide 62 · Amniotic embolism versus thrombotic PE

Similar abrupt respiratory compromise can have distinct underlying mechanisms.

Feature

Thrombotic PE

Amniotic fluid embolism

Usual setting

DVT / VTE risk

Labor / early postpartum

Dominant injury

Vascular obstruction

Mediator + coagulation injury

Associated finding

RV strain / infarction

DIC, neurologic dysfunction

Feature

Thrombotic PE

Amniotic fluid embolism

Slide 63 · Embolism can cause infarction—but not always

Vascular occlusion and tissue necrosis are distinct events.

Infarction requires ischemia sufficient to cause tissue death.

Available collaterals and rate of obstruction modify outcome.

A pulmonary thromboembolus can be clinically silent or cause shock without infarction.

Vessel obstruction

Residual supply?

Ischemic burden

Infarct or survival

Slide 64 · Compare mechanisms across embolic materials

The injury pathway differs by the constituent.

Type

Dominant pathway

Characteristic outcome

Thrombotic

Mechanical obstruction

PE / systemic infarction

Fat

Microvascular + biochemical

Respiratory + neurologic syndrome

Gas

Bubble blockage / inflammation

Ischemia / decompression illness

Amniotic

Coagulation + vasoactive

Shock / DIC

Type

Dominant pathway

Characteristic outcome

Slide 65 · Case: Postoperative sudden dyspnea

A patient develops abrupt dyspnea after prolonged immobilization following surgery.

A swollen calf had been noticed earlier but was not investigated.

What is the likely origin of the embolic material?

Trace the route from the originating vessel to the affected organ.

Interpret the mechanism

Suspected origin

Route

Expected destination

Slide 66 · Case interpretation: Venous thromboembolism

The likely mechanism is a fragment from a lower-extremity DVT.

Venous stasis supports formation of a deep-vein thrombus.

Embolus traverses IVC → right heart → pulmonary artery.

Severity depends on pulmonary vascular burden and RV response.

DVT

IVC

Right heart

Pulmonary artery

Slide 67 · Case: Fracture followed by systemic signs

Two days after a long-bone fracture, a patient develops respiratory distress and confusion.

Thrombocytopenia and petechiae accompany the deterioration.

What embolic syndrome best unifies the findings?

Which two injury pathways are involved?

Interpret the mechanism

Time course

Multiorgan pattern

Mechanism

Slide 68 · Case interpretation: Fat embolism syndrome

Marrow fat enters damaged venules and injures the microcirculation.

The 1–3-day latency is characteristic of the textbook description.

Mechanical occlusion is supplemented by fatty-acid toxicity.

Respiratory and cerebral abnormalities combine with cytopenias.

Long-bone injury

Fat microemboli

Endothelial + platelet injury

FES

Slide 69 · Case: Neurologic symptoms after rapid ascent

A diver ascends quickly and develops joint pain and neurologic disturbances.

No thrombus formation is required to explain this embolic syndrome.

Identify the source of intravascular gas.

Explain why recompression and slow decompression are effective.

Interpret the mechanism

Pressure change

Bubble source

Treatment principle

Slide 70 · Case interpretation: Decompression sickness

Nitrogen bubbles emerge as ambient pressure falls too rapidly.

High-pressure exposure increased dissolved nitrogen.

Rapid ascent created tissue supersaturation and bubbles.

Recompression supports redissolution; Controlled ascent permits elimination.

High-pressure exposure

Rapid ascent

Nitrogen bubbles

Recompression

Slide 71 · Case: Collapse immediately after delivery

A postpartum patient acutely develops cyanosis, shock, and a coagulopathy.

Consider a mechanism beyond pulmonary vascular plugging alone.

What embolic syndrome is characteristic of this setting?

What accounts for DIC and severe cardiovascular dysfunction?

Interpret the mechanism

Obstetric context

Pulmonary crisis

Coagulopathy

Slide 72 · Case interpretation: Amniotic fluid embolism

Amniotic material triggers severe vascular and coagulation responses.

Entry into maternal blood follows placental or uterine vascular disruption.

Tissue factor and immune-mediated responses contribute to DIC.

Vasoactive mediators can induce pulmonary hypertension and RV failure.

Maternal entry

Coagulation activation

Pulmonary vascular response

Shock / DIC

Slide 73 · High-yield classification by origin and target

Identify the source before assigning a destination or an outcome.

Venous thrombus → pulmonary artery.

Left cardiac or aortic source → systemic organ.

Right-to-left conduit → paradoxical arterial embolus.

Fat, gas, and amniotic material demand context-specific pathogenesis.

Venous DVT

Right heart

Lungs

Left-heart clot

Aorta

Organs

Venous clot

R→L shunt

Organs

Slide 74 · Five statements to retain

Every embolism case can be reduced to material, route, and injured vascular bed.

An embolus is detached material transported in blood.

Most emboli are thromboemboli; Nonthrombotic types matter.

Anatomic routing predicts the principal organ at risk.

Collateral circulation explains why occlusion may not cause infarction.

Fat, gas, and amniotic emboli add mechanisms beyond simple obstruction.

Embolic process

Material

Route

Lodging site

Tissue response

Slide 75 · References

Primary textbook reading on embolic pathology.

Robbins, Cotran & Kumar: Pathologic Basis of Disease. 11th ed. 2026.

Chapter 4: Hemodynamic Disorders, Thromboembolic Disease, and Shock.

Sections: thrombosis; embolism; pulmonary and systemic emboli.

Additional sections: fat, gas, amniotic fluid embolism, and infarction.