Atherosclerotic Stenosis

Slide 1 · ATHEROSCLEROTIC

STENOSIS

Schematic arterial cross-section

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · Learning objectives

Trace the progression from intimal atheroma to fixed stenosis.

Explain outward arterial remodeling and its eventual failure.

Relate lesion architecture and stenosis to chronic tissue ischemia.

Distinguish fixed flow limitation from sudden plaque disruption.

Slide 3 · Stenosis is a hemodynamic consequence of plaque growth

An atheroma occupies the arterial intima and can encroach on the lumen.

Progressive narrowing can reduce distal blood supply.

When perfusion becomes inadequate for tissue demand, ischemic injury develops.

Intimal plaque expands

Open lumen decreases

Distal flow becomes limited

Slide 4 · Atherosclerosis is an intimal-based arterial disease

Atheromas contain cells, matrix, lipid, and often calcification.

Enlarging plaques distort the vessel wall and eventually the blood channel.

Stenosis is one outcome; Rupture, thrombosis, and aneurysm are others.

Original editable schematic • not histology

Plaque

Slide 5 · Major arterial beds affected

Extensive disease involves lower abdominal aorta/iliac, coronary, and popliteal arteries.

Internal carotid arteries and vessels of the circle of Willis are also involved.

Mesenteric and renal arterial disease is relatively concentrated at ostia.

Aortoiliac

Coronary

Popliteal

Carotid / cerebral

Slide 6 · Lesions are patchy rather than uniformly circumferential

Most plaques occupy only part of the vessel perimeter.

Cross-sections therefore commonly show eccentric luminal narrowing.

Mixed stages of plaque development can coexist along one arterial tree.

Original editable schematic • not histology

Plaque

Slide 7 · Branch points are plaque-prone

Hemodynamic flow disturbances localize plaques to ostia and branching sites.

Nonlaminar flow changes endothelial behavior toward an atheroprone state.

This helps explain focal disease despite systemic exposure to risk factors.

Disturbed branch-point flow

Atheroprone endothelial state

Focal intimal plaque

Slide 8 · Endothelial dysfunction initiates the response-to-injury

Endothelium may be morphologically intact but functionally abnormal.

Increased permeability and leukocyte adhesion favor plaque development.

Hemodynamic disturbances, hypercholesterolemia, and inflammation are major drivers.

Hemodynamic / lipid insults

Permeability and adhesion

Intimal response to injury

Slide 9 · Intimal lipid accumulation sustains lesion growth

Lipoproteins accumulate within the vessel wall, especially modified LDL.

Cholesterol influx and insufficient removal favor lipid retention.

Intracellular and extracellular lipid become structural constituents of atheroma.

LDL enters arterial intima

Modified lipid is retained

Plaque lipid accumulates

Slide 10 · Foam cells contribute to early plaque formation

Macrophages and smooth muscle cells can accumulate modified lipids.

Lipid-laden cells are termed foam cells.

Cell death releases lipid and necrotic debris into the developing plaque.

Cells take up modified lipid

Foam cells accumulate

Dead cells release lipid

Slide 11 · Inflammation sustains atheroma progression

Monocytes and T lymphocytes enter the atherosclerotic lesion.

Cytokines and chemokines shape leukocyte and smooth muscle cell activity.

The process links lipid accumulation with cellular repair and injury.

Inflammatory cell influx

Cytokines and chemokines

Progressive atheroma

Slide 12 · Smooth muscle cells build a fibrous matrix

Medial smooth muscle cells migrate into the intima and proliferate.

They produce extracellular matrix, notably collagen and proteoglycans.

Matrix synthesis helps generate the fibrous plaque architecture.

SMCs migrate into intima

Collagen / ECM synthesis

Fibrous cap forms

Slide 13 · Fatty streaks precede some advanced plaques

Early lesions contain lipid-filled macrophages and appear as yellow streaks.

They produce little or no important flow disturbance.

Not every fatty streak progresses to a mature atheroma.

Foam cells

Fatty streak

Mature plaque

Possible, not inevitable, progression • schematic

Slide 14 · Plaque progression is not a single inevitable pathway

Lesions change as lipid, cells, and matrix accumulate.

Some become fibrotic and remain comparatively stable.

Others acquire features that favor sudden plaque disruption.

Intimal lesion

Fibrous plaque

Thin-cap lesion

Alternative plaque outcomes • no necessary sequence

Slide 15 · A mature plaque is an intimal mass

Gross atheromas are yellow-tan and raised above the arterial surface.

They may coalesce into larger lesions.

Expansion of this mass is the structural basis for later stenosis.

Original editable schematic • not histology

Plaque

Slide 16 · Four components define plaque composition

Cells: Smooth muscle cells, macrophages, and T lymphocytes.

Extracellular matrix: Collagen, elastic fibers, proteoglycans.

Intracellular/extracellular lipid and, in later lesions, calcification.

Cells

Matrix

Lipids

Calcification

Slide 17 · The fibrous cap faces the blood lumen

A superficial layer rich in smooth muscle cells and dense collagen.

Separates circulating blood from the underlying necrotic core.

Its matrix content helps determine the mechanical integrity of the plaque.

Original editable schematic • not histology

Plaque

Slide 18 · The necrotic core lies deep to the cap

Contains cholesterol, cholesterol esters, dead-cell debris, and foam cells.

Fibrin and thrombus-related material may be incorporated.

Lipid-rich debris occupies intimal space that can expand over time.

Original editable schematic • not histology

Plaque

Slide 19 · Plaque shoulders are relatively cellular

Lateral regions near the fibrous cap often contain inflammatory cells.

Macrophages, T lymphocytes, and smooth muscle cells intermingle there.

Plaque composition is therefore spatially heterogeneous.

Original editable schematic • not histology

Plaque

Slide 20 · Cholesterol clefts are a characteristic histologic clue

Cholesterol can form crystalline aggregates within the necrotic core.

Routine processing dissolves lipids and leaves empty cleft-like spaces.

Clefts are morphological evidence of prior plaque lipid accumulation.

Core lipid

Processing

Empty clefts

Slide 21 · Underlying media can become attenuated

The expanding plaque can compress the media.

Smooth muscle cell loss and elastic membrane attenuation may develop.

Plaque-related wall remodeling affects both lumen and vessel architecture.

Original editable schematic • not histology

Plaque

Slide 22 · Later plaques may become fibrocalcific

Calcification can accompany progressive extracellular matrix remodeling.

Some plaques consist predominantly of smooth muscle cells and fibrous tissue.

Fibrosis and calcification are not equivalent to complete luminal closure.

Original editable schematic • not histology

Plaque

Slide 23 · Plaques enlarge through several interacting processes

Cell death and degeneration add necrotic material.

Synthesis and breakdown of matrix alter plaque size and texture.

Organized thrombus and secondary calcification may add to the lesion.

Cell death and degeneration

Matrix remodeling

Larger and altered plaque

Slide 24 · Early plaque enlargement can spare the lumen

Outward remodeling expands the arterial wall around an enlarging plaque.

This compensation helps preserve luminal dimensions early.

The source names this adaptive process the Glagov phenomenon.

Original editable schematic • not histology

Slide 25 · Outward remodeling creates a temporary reserve

Plaque accumulation initially enlarges the vessel outer boundary.

The inner channel may appear relatively unchanged despite plaque burden.

Luminal caliber alone may therefore underrepresent early wall disease.

Feature

Compensated remodeling

Advanced uncompensated plaque

Wall response

Outward expansion

Limited further expansion

Luminal effect

Initially preserved

Progressive encroachment

Perfusion

Relatively maintained

May become inadequate

Slide 26 · Remodeling has finite capacity

Continued growth eventually exhausts outward enlargement.

Further plaque expansion projects into the blood channel.

The resulting stenosis is accompanied by reduced perfusion reserve.

Original editable schematic • not histology

Plaque

Slide 27 · Lumen and wall burden need not change together

A large plaque can coexist with comparatively preserved lumen early.

Later, even additional plaque growth can sharply reduce open area.

The site and stage of remodeling alter the anatomical appearance.

Normal

Compensated

Flow-limiting

Slide 28 · Critical stenosis produces tissue ischemia

Critical stenosis denotes narrowing sufficient to compromise oxygen delivery.

It is a physiologic consequence of an anatomical obstruction.

The threshold depends on vascular territory, collateral flow, and demand.

Major luminal narrowing

Inadequate blood delivery

Tissue ischemia

Slide 29 · A typical critical area reduction

In coronary and other circulations, the text gives approximately 70%–75% loss of luminal cross-sectional area.

This is a textbook contextual approximation, not a universal patient-specific cutoff.

Do not confuse area reduction with percentage diameter reduction.

Measure

Meaning

Luminal area

Cross-sectional open blood-channel area

Area loss

Reduction relative to an unobstructed reference

Clinical interpretation

Requires flow demand / collateral context

Slide 30 · Narrowing matters because it limits flow reserve

Obstruction restricts the delivery of blood downstream.

Symptoms are particularly evident when tissue demand increases.

Baseline perfusion can be relatively adequate before exertion.

Fixed flow limitation

Demand increases

Supply reserve is inadequate

Slide 31 · Supply–demand mismatch is the immediate mechanism

Nutrient and oxygen supply depend on arterial perfusion.

Metabolic demand changes with organ activity.

Ischemia occurs when demand exceeds the supply the stenosed circulation can deliver.

Tissue metabolic demand

Limited available arterial flow

Ischemic supply–demand gap

Slide 32 · Coronary stenosis may present as exertional angina

Coronary flow-limiting plaques may supply sufficient blood at rest.

Exercise increases myocardial metabolic requirements.

Transient mismatch can produce stable angina.

Fixed coronary stenosis

Exertional demand rises

Transient myocardial ischemia

Slide 33 · Stable angina links obstruction with reproducible stress

A fixed lesion limits augmentation of coronary flow.

Provocation occurs when myocardial demand increases.

The symptom reflects ischemia, not necessarily an acute plaque rupture.

Feature

Resting state

Exertional state

Demand

Lower

Increased

Flow limitation

Can be compensated

May become apparent

Consequence

Often no pain

Possible angina

Slide 34 · Chronic cardiac ischemia can accumulate damage

Progressive stenosis causes chronically diminished myocardial perfusion.

The source lists chronic ischemic heart disease as a consequence.

This is distinct from acute thrombotic infarction after plaque change.

Plaque

Narrowing

Hypoperfusion

Chronic ischemia

Slide 35 · The coronary bed is only one target

Atherosclerotic stenoses can compromise multiple arterial circulations.

Symptoms depend on the tissues supplied by the obstructed artery.

The same vascular mechanism yields different organ manifestations.

Heart

Brain

Bowel

Limbs

Slide 36 · Intermittent claudication reflects limb flow limitation

Peripheral arterial stenosis reduces perfusion to working limb muscles.

Walking increases oxygen demand relative to available flow.

Ischemic discomfort is a clinical consequence of this mismatch.

Peripheral arterial stenosis

Exercise increases demand

Ischemic muscle discomfort

Slide 37 · Atherosclerosis can compromise cerebral perfusion

Cerebral arterial supply is a major site of symptomatic disease.

Persistent flow limitation is associated with ischemic encephalopathy.

Local distribution and available collaterals influence tissue effects.

Arterial lesion

Reduced supply

Cerebral ischemia

Slide 38 · Mesenteric disease can produce bowel ischemia

Mesenteric arterial occlusion is among the consequences described.

Bowel injury reflects inadequate arterial delivery to intestinal tissue.

The degree of collateralization modifies severity.

Mesenteric arterial occlusion

Reduced intestinal perfusion

Bowel ischemia

Slide 39 · Peripheral disease can progress to tissue loss

Severe arterial insufficiency may result in ischemic injury of the extremity.

The parent section identifies gangrene of the legs as a major complication.

Extent of injury depends on residual supply and tissue requirements.

Marked distal flow reduction

Sustained tissue ischemia

Possible gangrene

Slide 40 · Renal arteries are not uniformly involved

Symptomatic atherosclerotic disease can involve the renal circulation.

Relative sparing of renal arteries except at their origins.

An ostial lesion illustrates why anatomical site matters.

Aortic branch

Renal ostium

Renal perfusion

Slide 41 · Collateral arteries modify the consequences

When a stenosis develops slowly, adjacent smaller arteries may enlarge.

Newly effective collateral routes partially preserve distal perfusion.

Collateral compensation is limited and varies between organs.

Slowly evolving stenosis

Adjacent vessels enlarge

Partial perfusion compensation

Slide 42 · Rate of narrowing affects the adaptive response

Gradual obstruction can permit recruitment and enlargement of collateral pathways.

Sudden occlusion may leave less opportunity for compensation.

Chronology of vessel obstruction is clinically important.

Feature

Slow stenosis

Acute occlusion

Time course

Gradual

Sudden

Adaptation

Collateral enlargement possible

Limited time to adapt

Possible effect

Chronic ischemia

Acute ischemic injury

Slide 43 · Vessel anatomy changes the effect of equal narrowing

The territory supplied by the artery determines exposed tissue.

Existing alternative routes determine collateral supply.

Organ metabolic demand determines whether residual supply is sufficient.

Supply territory

Collateral routes

Metabolic demand

Slide 44 · Stenosis and plaque instability are distinct properties

Plaque volume and luminal encroachment govern fixed obstruction.

Fibrous cap composition and inflammation influence rupture propensity.

A noncritical lesion may still undergo sudden destabilization.

Feature

Fixed stenosis

Plaque vulnerability

Principal property

Degree of narrowing

Cap structure / inflammation

Common effect

Chronic hypoperfusion

Sudden plaque change

Relationship

Can coexist

Not defined by stenosis alone

Slide 45 · Stable plaques are not necessarily harmless

A relatively thick fibrous cap may make rupture less likely.

The same lesion can progressively occupy the vessel lumen.

A stable, fibrotic plaque may therefore still cause critical stenosis.

Original editable schematic • not histology

Plaque

Slide 46 · The fibrous cap controls a different clinical risk

Collagen-rich caps increase mechanical integrity.

Thin caps over lipid-rich cores are more prone to sudden rupture.

Neither feature alone directly measures the severity of luminal narrowing.

Feature

Thick fibrous cap

Thin fibrous cap

Structural feature

More collagen / matrix

Less supporting matrix

Clinical tendency

Greater stability

Greater rupture susceptibility

What is not implied

Normal lumen

Critical stenosis

Slide 47 · Acute plaque change is a different pathway to occlusion

Rupture or erosion exposes thrombogenic plaque constituents.

Superimposed thrombus can rapidly obstruct an artery.

This abrupt event differs from slow luminal loss due to plaque enlargement.

Plaque rupture or erosion

Thrombus forms

Acute vascular obstruction

Slide 48 · Intraplaque hemorrhage can suddenly expand a lesion

Bleeding may arise from the cap or neovessels within the plaque.

A contained hematoma adds volume to the atheroma.

This secondary change is not synonymous with gradual fibrotic stenosis.

Cap / neovessel hemorrhage

Blood accumulates in plaque

Rapid increase in plaque volume

Slide 49 · Chronic ischemia versus acute infarction

Fixed stenosis mainly restricts sustained or demand-related flow.

Plaque rupture with thrombosis can cause acute arterial obstruction.

Organ injury may be chronic, episodic, or abrupt depending on mechanism.

Feature

Progressive narrowing

Thrombotic plaque event

Mechanism

Plaque encroachment

Rupture / erosion plus thrombosis

Typical tempo

Gradual

Abrupt

Illustrative outcome

Stable angina / claudication

Acute tissue infarction

Slide 50 · A modest lumen defect does not rule out acute risk

The adjacent source notes many abruptly complicated coronary plaques were previously noncritical.

Thus luminal stenosis and risk of rupture cannot be treated as identical.

A purely geometric interpretation of atherosclerosis is incomplete.

Previously noncritical plaque

Unexpected plaque disruption

Possible acute thrombosis

Slide 51 · Morphology and clinical consequences must be paired

Macroscopic plaque burden establishes chronic arterial disease.

Cross-sectional architecture demonstrates eccentric narrowing and media remodeling.

Functional effects require considering the downstream organ and supply reserve.

Plaque morphology

Lumen geometry

Distal demand

Slide 52 · Case exercise: Exertional chest discomfort

CLINICOPATHOLOGIC APPLICATION

A patient develops chest discomfort during walking uphill.

At rest, myocardial demand is lower and symptoms may resolve.

Explain how a fixed coronary atheroma can account for this pattern.

Reason through the mechanism; Answer in presenter notes.

Slide 53 · Case analysis: What remodeling explains

CLINICOPATHOLOGIC APPLICATION

An eccentric coronary plaque is large, but the lumen is initially relatively preserved.

Later sections show a smaller lumen despite only incremental plaque growth.

Identify the compensatory process and why it becomes inadequate.

Reason through the mechanism; Answer in presenter notes.

Slide 54 · Case exercise: Exercise-related calf discomfort

CLINICOPATHOLOGIC APPLICATION

A patient experiences calf pain during walking that is absent at rest.

The popliteal artery has marked plaque-related narrowing.

Connect the clinical pattern to muscle oxygen demand and blood supply.

Reason through the mechanism; Answer in presenter notes.

Slide 55 · Case exercise: Chronic mesenteric flow limitation

CLINICOPATHOLOGIC APPLICATION

A patient has extensive atherosclerotic disease involving mesenteric vessel origins.

A distal intestinal territory receives limited arterial perfusion.

Predict the central tissue-level consequence without assuming acute plaque rupture.

Reason through the mechanism; Answer in presenter notes.

Slide 56 · Case analysis: Narrowing is not the whole story

CLINICOPATHOLOGIC APPLICATION

Two patients have similar anatomical stenoses but different degrees of ischemia.

One has slowly enlarging collateral routes around the obstruction.

What additional variables should be evaluated conceptually?

Reason through the mechanism; Answer in presenter notes.

Slide 57 · Case analysis: Stable plaque versus acute event

CLINICOPATHOLOGIC APPLICATION

One lesion causes exertional angina through longstanding fixed narrowing.

Another previously noncritical plaque ruptures and becomes thrombosed.

Explain the different mechanisms rather than judging both by stenosis alone.

Reason through the mechanism; Answer in presenter notes.

Slide 58 · Interpret the lesion from wall to organ

Endothelial dysfunction, lipid retention, inflammation, and matrix deposition build an atheroma.

Outward remodeling masks early luminal effects; Later growth causes obstruction.

Clinical injury emerges according to vascular supply, collaterals, and demand.

Atheroma grows in arterial wall

Compensation then stenosis

Organ supply–demand ischemia

Slide 59 · Three distinctions prevent common errors

Plaque burden is not identical to luminal stenosis.

Anatomic stenosis is not identical to tissue ischemia.

Plaque instability is not identical to critical fixed narrowing.

Burden ≠ narrowing

Narrowing ≠ ischemia

Instability ≠ stenosis

Slide 60 · Reference and source boundaries

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

Core: “Atherosclerotic Stenosis,” pp. 456–458; parent morphology and pathogenesis, pp. 452–456.

Adjacent “Acute Plaque Change,” p. 458, used only for mechanism contrasts.

Anatomical drawings are editable schematics, not diagnostic photomicrographs.