Aortic Stenosis and Atresia

Slide 1 · Aortic stenosis and atresia

Congenital obstruction of the left ventricular outflow tract

Recognize where obstruction occurs, how cardiac structure responds, and why ductal patency matters in severe neonatal disease.

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · Learning objectives

Localize congenital obstruction to the valve, below the cusps, or above the valve.

Relate valvular morphology to impaired systolic ejection and ventricular pressure load.

Describe the severe stenosis–atresia–hypoplastic left heart spectrum.

Explain the importance of the patent ductus arteriosus and compare the three anatomic levels.

Slide 3 · Aortic outflow disease belongs to obstructive CHD

Congenital heart disease comprises structural abnormalities present at birth.

Obstructive lesions narrow a chamber, valve, or great vessel; Complete developmental obstruction is atresia.

Aortic stenosis affects the left ventricular outflow route into the systemic circulation.

Shunts and obstructions are distinct hemodynamic categories, although complex defects may coexist.

Ascending aorta

Left ventricle

Slide 4 · Anatomic route: Ventricle → valve → aorta

The site of a fixed narrowing determines which structure is malformed.

LEFT VENTRICLE

Chamber

AORTIC VALVE

Cusps / commissures

ASCENDING AORTA

Great vessel

Schematic: Direction of normal antegrade ejection

Slide 5 · Three distinct levels of narrowing

All three impair the left ventricular outflow pathway, but the primary tissue lesion differs.

SUPRAVALVULAR

Ascending aorta

VALVULAR

Valve cusps

SUBVALVULAR

Subaortic collar

Slide 6 · Stenosis and atresia are not synonyms

Stenosis

An outflow lumen remains, but is narrowed.

Blood can traverse the affected segment.

Consequences depend strongly on severity.

Atresia

The outflow orifice is completely obstructed.

Antegrade flow across that level is absent.

Systemic output may require an alternative route.

Slide 7 · The fundamental pathology question

WHERE?

Identify the exact level

WHAT?

Characterize the structural lesion

THEN?

Determine flow and ventricular effects

HOW SEVERE?

Assess duct dependence

Causal sequence / anatomic reasoning schematic

Slide 8 · Most congenital aortic valve stenosis is isolated

The valvular lesion as isolated in 80% of cases.

“Isolated” describes the lesion’s association status, not the severity of obstruction.

Severe left ventricular outflow obstruction can instead form part of hypoplastic left heart syndrome.

Anatomic context is essential before predicting clinical behavior.

Anatomic reasoning

Isolated valve lesion

The presence or absence of associated malformations must be assessed.

Schematic

Slide 9 · Aortic stenosis among congenital malformations

Selected lesion

Incidence per million live births

Share of tabulated defects

Aortic stenosis

388

4%

Pulmonary stenosis

836

8%

Coarctation of the aorta

492

5%

Values are textbook table entries; The underlying table excludes bicuspid aortic valves.

Slide 10 · Congenital defects reflect cardiac morphogenesis

Major cardiovascular structures form during embryonic weeks 3–8.

Cardiac progenitors contribute to chambers, outflow tracts, and supporting tissues.

Developmental errors can be localized to one valve or involve a broad segment of the left heart.

Anatomic severity at birth reflects developmental consequences, not merely postnatal remodeling.

Anatomic reasoning

Embryonic morphogenesis

A fetal structural lesion can affect later chamber growth.

Schematic

Slide 11 · Etiology: Avoid assuming one causal gene

CHD may reflect genetic and environmental influences on cardiac morphogenesis.

The broad CHD chapter emphasizes that the precise cause is unknown in most cases.

A named molecular association is not established for every valvular stenosis.

The defined genetic association in this topic concerns some supravalvular lesions and elastin.

Anatomic reasoning

Molecular interpretation

Only report causal associations supported by the source.

Schematic

Slide 12 · Valvular obstruction is a cusp-level lesion

The obstruction resides at the moving cusps, not in an independent wall segment.

Ascending aorta

Left ventricle

Valvular morphology varies among affected hearts.

Altered cusps or commissures can restrict the opening.

This is distinct from a fibrous ring below the cusps.

Slide 13 · Hypoplastic cusps: Insufficient cusp development

Hypoplastic aortic cusps are abnormally small.

Cusp size is an anatomic descriptor, not a measured severity grade in the source.

The essential diagnostic focus is restricted valvular anatomy and impaired outflow.

A schematic cannot replace gross specimen inspection.

Aortic cusp morphology

Small cusps

Schematic · not a specimen

Slide 14 · Dysplastic cusps: Thickened and nodular

Dysplasia produces thickened, nodular aortic valve cusps.

This is a morphologic description of congenital tissue abnormality.

Cusp thickening can contribute to reduced effective orifice opening.

Do not infer a particular microscopic composition without source evidence.

Aortic cusp morphology

Thickened, nodular cusps

Schematic · not a specimen

Slide 15 · Commissural abnormalities alter valve opening

Congenital valves can be abnormal in the number of commissures.

Valves usually having one commissure or none among these anomalies.

Commissures define cusp separation and functional opening geometry.

Commissural abnormalities are distinct from cusp hypoplasia and dysplasia, though they may coexist.

Aortic cusp morphology

Altered commissural pattern

Schematic · not a specimen

Slide 16 · Valvular morphology can be heterogeneous

Description

Primary abnormality

What it changes

Hypoplastic

Small cusps

Cusp development

Dysplastic

Thickened, nodular cusps

Cusp architecture

Abnormal commissures

One or no commissures

Opening configuration

Slide 17 · What becomes obstructed during systole?

A small effective outlet restricts blood ejection from the left ventricle into the aorta.

Ascending aorta

Left ventricle

Ventricular ejection requires passage through the valve.

Narrowing increases resistance to forward flow.

The obstruction is anatomically upstream of the systemic arteries.

Slide 18 · A pressure load develops proximal to obstruction

VALVE NARROWING

Reduced outflow passage

LV OUTFLOW RESISTANCE

Higher systolic pressure burden

CHRONIC RESPONSE

Left ventricular hypertrophy

Causal sequence / anatomic reasoning schematic

Slide 19 · Pressure hypertrophy is a ventricular response

Robbins explicitly associates congenital obstruction with left ventricular pressure hypertrophy.

The myocardium adapts to a sustained pressure burden by increasing muscle mass.

Hypertrophy is a response to loading, not a correction of the malformed valve.

Do not confuse acquired hypertrophy with prenatal chamber hypoplasia.

Anatomic reasoning

Obstruction

LV pressure load

Myocardial hypertrophy

Schematic

Slide 20 · Obstruction may be tolerated despite hypertrophy

Unless stenosis is very severe, it as generally well tolerated.

Clinical tolerance does not mean the left ventricle remains structurally normal.

Pressure hypertrophy may still develop despite limited symptoms.

Severe ventricular remodeling carries a risk of sudden cardiac death.

Anatomic reasoning

Anatomic stenosis

Variable physiologic tolerance

Residual risk with LVH

Schematic

Slide 21 · Why a systolic murmur can occur

During systolic ejection, blood moves across a narrowed outflow pathway.

The resulting disturbed flow can produce an audible systolic murmur.

Robbins specifically highlights a prominent systolic murmur in subaortic stenosis.

A murmur suggests turbulent flow; It does not identify the exact level by itself.

Anatomic reasoning

Systolic ejection

Disturbed flow

Murmur ± thrill

Schematic

Slide 22 · A thrill implies strong palpable flow disturbance

A thrill is a palpable vibration accompanying a forceful murmur.

Subaortic stenosis can have a thrill according to the textbook.

The examination finding reflects flow disturbance rather than histologic subtype.

Define the anatomic obstruction separately from its clinical sign.

Anatomic reasoning

Systolic ejection

Disturbed flow

Murmur ± thrill

Schematic

Slide 23 · Anatomic severity changes the consequence

Less severe stenosis

A residual outflow channel is present.

Symptoms may be absent or limited.

Chronic left ventricular pressure load is still possible.

Critical obstruction / atresia

Forward aortic outflow is profoundly restricted or absent.

Developmental left-heart hypoplasia may coexist.

Maintenance of systemic flow can become duct-dependent.

Slide 24 · Severe congenital obstruction can change growth

EARLY LV OUTFLOW OBSTRUCTION

Severe stenosis or atresia

DEVELOPMENTAL CONSEQUENCE

Small left ventricle

GREAT-VESSEL CONSEQUENCE

Hypoplastic ascending aorta

Causal sequence / anatomic reasoning schematic

Slide 25 · Atresia abolishes normal valve-level ejection

Aortic valvular atresia is complete obstruction at the aortic valve level.

Blood cannot pass antegrade from the left ventricle across an atretic valve.

The circulation must rely on an alternative route to supply the aorta.

In the severe constellation, the patent ductus arteriosus supplies that route.

Ascending aorta

Left ventricle

Absent effective valve opening

Slide 26 · Prenatal hypoplasia differs from later atrophy

Hypoplasia

Reduced chamber volume and muscle mass develop before birth.

Represents insufficient development or growth.

Severe left ventricular outflow disease may produce it.

Atrophy

A decrease in chamber mass developing after birth.

A different temporal/pathologic category.

Should not be substituted for congenital LV hypoplasia.

Slide 27 · The hypoplastic left ventricle

Severe congenital aortic stenosis or atresia may produce a small left ventricle.

An inadequate left ventricular chamber cannot be assumed to provide normal systemic output.

The abnormality involves the chamber, not just the orifice.

This is a major step toward the hypoplastic left heart syndrome phenotype.

Ascending aorta

Left ventricle

Slide 28 · The ascending aorta may also be hypoplastic

The ascending aorta can be underdeveloped along with the left ventricle.

Aortic caliber matters because the vessel must deliver flow to the upper systemic circulation and coronary origins.

Valve obstruction and great-vessel hypoplasia form a linked severe morphology.

The exact extent of the hypoplasia is not specified in the excerpt.

Ascending aorta

Left ventricle

Slide 29 · Endocardial fibroelastosis is an associated lesion

Severe cases may exhibit dense left ventricular endocardial fibroelastosis.

A striking porcelain-like endocardial appearance.

This is an associated morphologic finding, not required in every case.

Do not present a synthetic photomicrograph as evidence of this lesion.

Ascending aorta

Left ventricle

Endocardial fibroelastosis (source description)

Slide 30 · Hypoplastic left heart: An anatomic constellation

The syndrome designation reflects a combination of severe structural abnormalities.

OUTFLOW OBSTRUCTION

Severe aortic stenosis / atresia

UNDERDEVELOPMENT

LV and ascending aorta

ASSOCIATED CHANGE

May have fibroelastosis

Severe aortic stenosis or atresia

Hypoplastic left ventricle

Hypoplastic ascending aorta; Fibroelastosis may coexist

Conceptual schematic; Actual anatomy varies

Slide 31 · Not every congenital aortic stenosis is HLHS

Isolated valvular stenosis

A focal congenital valve lesion.

Can be well tolerated when not very severe.

Does not automatically imply chamber hypoplasia.

Hypoplastic left heart syndrome

Severe obstructive left-heart malformation.

Includes underdeveloped LV and ascending aorta.

Systemic/coronary flow depends on ductal patency description.

Slide 32 · The ductus becomes a systemic lifeline

In severe aortic atresia/HLHS, the patent ductus arteriosus permits blood to reach the aorta.

RIGHT VENTRICLE

Pumps into pulmonary artery

PULMONARY ARTERY

Ductal connection

PATENT DUCTUS

Alternate pathway

AORTA

Systemic perfusion

The ductus connects pulmonary arterial blood flow with the aorta.

This bypasses the unusable native left ventricular outflow route.

The systemic circulation becomes vulnerable to ductal closure.

Conceptual schematic; Actual anatomy varies

Slide 33 · Why the coronary arteries also depend on flow

Ductal patency is needed to supply both the aorta and coronary arteries.

PATENT DUCTUS

Source route

AORTIC ARCH / ROOT

Flow can reach proximal aorta

CORONARY ARTERIES

Require perfusion

The coronary ostia arise from the proximal aortic root.

In the severe atretic pathway, systemic supply can reach the arch/root by the duct-dependent route.

Loss of the duct removes a critical route for coronary as well as systemic perfusion.

Conceptual schematic; Actual anatomy varies

Slide 34 · Ductal patency and ductal closure

Patent ductus

An alternative pathway remains open.

Aorta and coronary circulation can receive blood.

Severe obstruction may still be physiologically precarious.

Ductus closes

The alternative pathway is lost.

Systemic and coronary perfusion may collapse.

Closure in week 1 as generally lethal in this syndrome.

Slide 35 · The critical transition occurs after birth

AT BIRTH

Ductal connection may be open

POSTNATAL TRANSITION

Ductal closure can occur

SEVERE HLHS

Loss of essential systemic route

CONSEQUENCE

Usually lethal without maintained patency

Causal sequence / anatomic reasoning schematic

Slide 36 · The first week is a decisive clinical window

Duct closure during the first week of life as generally lethal in HLHS.

The mechanism is loss of blood supply to the aorta and coronary arteries.

This mortality statement applies to the duct-dependent severe constellation—not every congenital aortic stenosis.

Avoid equating “isolated valvular stenosis” with neonatal duct dependence.

Anatomic reasoning

Birth

Ductal closure (week 1)

Threat to duct-dependent flow

Schematic

Slide 37 · Clinical interpretation starts with duct dependence

First, decide whether there is a residual route for left ventricular ejection.

Second, recognize whether the left ventricle and ascending aorta are adequately developed.

Third, ask whether the patent ductus supplies essential systemic blood flow.

A change in ductal patency can change physiology even when valve anatomy is unchanged.

Anatomic reasoning

Outflow patency?

Left-heart hypoplasia?

Duct needed?

Schematic

Slide 38 · Integrating severe aortic obstruction

The risk arises from combined obstruction, underdevelopment and loss of the alternative circulation.

STRUCTURAL BLOCK

Atresia / critical narrowing

SMALL LEFT HEART

LV / aortic hypoplasia

DUCTAL RELIANCE

Systemic and coronary flow

Aortic obstruction → reduced antegrade route

LV / ascending aorta hypoplasia → limited native systemic pathway

PDA-dependent perfusion → hazard of ductal closure

Conceptual schematic; Actual anatomy varies

Slide 39 · Subaortic stenosis lies below the cusps

The narrowing is in the left ventricular outflow tract proximal to the valve.

Ascending aorta

Left ventricle

The aortic cusps sit above the obstructing lesion.

The stenotic segment is not a malformed ascending aortic wall.

Localization is essential for morphologic classification.

Slide 40 · The subaortic lesion is fibrous tissue

A thickened ring or collar beneath the aortic cusps.

The ring consists of dense endocardial fibrous tissue.

Its encroachment on the outflow passage creates the stenotic lesion.

The named pathologic structure is a discrete subvalvular collar.

Ascending aorta

Left ventricle

Slide 41 · A fibrous collar and cusp dysplasia differ

Subaortic fibrous ring

Located below the cusps.

Made of dense endocardial fibrous tissue.

Constrains the LV outflow passage.

Valvular dysplasia

Located within the aortic cusps.

Cusps are thickened and nodular.

Restricts valvular opening.

Slide 42 · Subaortic obstruction has examination clues

A prominent systolic murmur is typical description.

A palpable thrill may accompany the murmur.

These clues indicate obstructed ejection but do not substitute for anatomical localization.

The underlying lesion remains a fibrous subvalvular collar.

Anatomic reasoning

Systolic ejection

Disturbed flow

Murmur ± thrill

Schematic

Slide 43 · Subaortic obstruction produces a pressure response

ENDOCARDIAL FIBROUS RING

Subvalvular outflow narrowing

EJECTION RESISTANCE

Pressure overload of LV

TISSUE RESPONSE

Left ventricular hypertrophy

CLINICAL IMPLICATION

Hypertrophy associated with risk

Causal sequence / anatomic reasoning schematic

Slide 44 · Supravalvular stenosis lies in the aortic wall

The primary abnormality is superior to the aortic valve.

Ascending aorta

Left ventricle

The ascending aortic wall is thickened and constricted.

The condition as congenital aortic dysplasia.

The obstruction is arterial, rather than a malformed cusp or subvalvular membrane.

Slide 45 · Supravalvular stenosis: Vessel wall pathology

Congenital dysplasia affects the ascending aorta.

Wall thickening reduces the available luminal caliber.

Constriction above the valve impedes left ventricular ejection.

The structural target is the aortic wall itself.

Ascending aorta

Left ventricle

Slide 46 · Elastin mutations can cause supravalvular disease

ELASTIN GENE MUTATION

Altered elastin biology

DEVELOPMENTAL DISRUPTION

Elastin–smooth muscle cell interactions

AORTIC MORPHOGENESIS

Abnormal wall development

MORPHOLOGY

Supravalvular narrowing

Causal sequence / anatomic reasoning schematic

Slide 47 · Elastin–smooth muscle interactions matter

Elastin is more than a passive structural component of the aortic wall.

Elastin–smooth muscle cell interactions to aortic morphogenesis.

Disrupted developmental signaling/structural interaction can contribute to constriction.

This is a supported mechanism for some supravalvular disease, not a universal cause of all aortic obstruction.

Anatomic reasoning

Elastin

Smooth muscle cell

Aortic morphogenesis

Schematic

Slide 48 · Genotype and lesion level must be separated

Supported specific association

Elastin gene mutation.

Supravalvular aortic stenosis.

Abnormal aortic wall development.

Not established by this excerpt

The same cause for all valvular stenosis.

A single genetic explanation for subaortic collars.

A genetic result sufficient to grade clinical severity.

Slide 49 · Compare the three structural lesions

Level

Primary abnormality

Main structure affected

Subvalvular

Dense endocardial fibrous collar

LV outflow below cusps

Valvular

Small/dysplastic cusps; commissures abnormal

Aortic valve

Supravalvular

Dysplastic, thickened, constricted wall

Ascending aorta

Slide 50 · The same pressure response may have different causes

Anatomic cause

Obstruction located at

LV effect

Cusp malformation

Valve

Pressure hypertrophy may develop

Fibrous collar

Below valve

Pressure hypertrophy may develop

Aortic wall narrowing

Above valve

Outflow load is increased

Slide 51 · Congenital aortic stenosis versus coarctation

Aortic stenosis / atresia

Obstruction at, below, or just above the aortic valve.

May produce left ventricular hypertrophy.

Severe valve atresia may be associated with HLHS.

Coarctation of the aorta

Discrete or tubular narrowing of the aorta near the ductal region.

May produce proximal hypertension and collateral flow.

A different great-vessel location and disease unit.

Slide 52 · Aortic and pulmonary outflow atresia contrast

Aortic atresia

Obstructs left-sided systemic outflow.

Severe disease may have hypoplastic left ventricle.

Patent ductus needed for aortic/coronary supply.

Pulmonary atresia

Obstructs right-sided pulmonary outflow.

May have hypoplastic right ventricle.

Patent ductus can provide pulmonary blood supply.

Slide 53 · Four structural questions organize evaluation

LEVEL

Below / at / above cusps?

MORPHOLOGY

Collar / cusps / aortic wall?

LV RESPONSE

Hypertrophy or hypoplasia?

SYSTEMIC ROUTE

Duct-dependent perfusion?

Causal sequence / anatomic reasoning schematic

Slide 54 · Do not confuse clinical severity with anatomy

Lesion level determines which tissue must be characterized.

Severity determines how much flow is obstructed and whether compensation is adequate.

Developmental timing determines whether the ventricle is hypoplastic rather than merely hypertrophied.

Duct dependence is a circulatory condition, not a synonym for all congenital stenosis.

Anatomic reasoning

Location

Morphology

Physiologic dependence

Schematic

Slide 55 · Morphology-to-clinical correlation

Observation

Pathologic interpretation

Consequence

Small or nodular cusps

Valvular anomaly

Cusp-level narrowing

Fibrous subaortic collar

Endocardial lesion

Subvalvular narrowing

Ascending aortic thickening

Congenital aortic dysplasia

Supravalvular narrowing

Hypoplastic LV + aorta

Severe developmental obstruction

Consider HLHS and duct dependence

Slide 56 · Case application: An isolated valve lesion

Hypothetical teaching scenario

Teaching scenario: A child is found to have congenital abnormal aortic cusps. The left ventricle and ascending aorta are adequately developed, and there is no suggestion of duct-dependent systemic flow.

Apply the pathology:

What information supports an isolated valvular lesion rather than hypoplastic left heart syndrome?

Slide 57 · Case reasoning: Isolated does not mean harmless

Preserved left-heart growth argues against the severe hypoplastic constellation.

An abnormal valve can be an isolated lesion.

A small residual opening can still produce ventricular pressure load.

The presence of LV hypertrophy does not itself establish HLHS.

Slide 58 · Case application: Duct-dependent newborn

Hypothetical teaching scenario

Teaching scenario: A newborn has severe aortic valve obstruction, a diminutive left ventricle and ascending aorta, and systemic blood flow reliant on an open ductus arteriosus.

Apply the pathology:

Which anatomic constellation is present, and why is duct closure critical?

Slide 59 · Case reasoning: A duct-dependent syndrome

This matches the severe hypoplastic left heart constellation.

Aortic stenosis/atresia coexists with LV and ascending aortic hypoplasia.

The PDA supplies a route for systemic and coronary perfusion.

Closure in the first week is generally lethal unless patency is preserved.

Slide 60 · Case application: A lesion above the cusps

Hypothetical teaching scenario

Teaching scenario: The valve cusps are not the primary lesion. Instead, congenital thickening and constriction affect the ascending aorta above the valve.

Apply the pathology:

Which category best localizes the defect, and what molecular association does Robbins describe?

Slide 61 · Case reasoning: Supravalvular dysplasia

This is supravalvular aortic stenosis.

The pathologic tissue is the ascending aortic wall.

Elastin gene mutations can disrupt elastin–smooth muscle interactions.

The resulting abnormal aortic morphogenesis can produce supravalvular constriction.

Slide 62 · Integrated diagnostic synthesis

ANATOMIC LEVEL

Name the exact lesion

PATHOLOGIC SUBSTRATE

Cusp / endocardial collar / aortic wall

CARDIAC RESPONSE

Hypertrophy vs severe hypoplasia

SURVIVAL DETERMINANT

Ductal flow in HLHS

Causal sequence / anatomic reasoning schematic

Slide 63 · Essential pathology conclusions

Congenital obstruction occurs at three anatomical levels with different pathologic substrates.

Valvular abnormalities include small or dysplastic cusps and altered commissures.

Proximal pressure overload explains left ventricular hypertrophy and its potential risks.

Severe atresia with LV/aortic hypoplasia is duct-dependent and potentially lethal after duct closure.

SUPRAVALVULAR

Ascending aorta

VALVULAR

Valve cusps

SUBVALVULAR

Subaortic collar

Slide 64 · Primary reference

Robbins, Cotran & Kumar. Pathologic Basis of Disease. 11th edition (2026).

Chapter: The Heart — sections “Congenital Heart Disease,” “Obstructive Lesions,” and “Aortic Stenosis and Atresia.”

Hoffman JI, Kaplan S. The incidence of congenital heart disease. J Am Coll Cardiol. 2002;39(12):1890–1900.