Pulmonary Hypertension

Slide 1 · Pulmonary Hypertension

Mechanisms • vascular morphology • clinicopathologic integration

Elevated resistance

Arterial remodeling

Right-heart stress

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · Learning objectives

A pathology-centered approach to pulmonary hypertension (PH)

Differentiate raised pulmonary arterial pressure from pulmonary arterial hypertension (PAH).

Classify major etiologies by the compartment generating pressure.

Trace vascular remodeling to right ventricular dysfunction.

Recognize medial hypertrophy, intimal fibrosis, and plexiform lesions.

Interpretation

Clinical correlations and contemporary hemodynamic definitions are identified separately.

Slide 3 · Pulmonary circulation: Low-resistance circuit

Mechanistic sequence

Right ventricle

Pulmonary arteries

Alveolar capillary bed

Pulmonary veins / left atrium

WHY IT MATTERS

Pressure rises when flow increases, distal resistance increases, or downstream venous pressure is elevated.

Slide 4 · Definition: Distinguish textbook and current practice

Definition

Mean pulmonary artery pressure

Interpretation

Robbins source (11th ed.)

≥25 mm Hg at rest

Textbook passage retains the historical cutoff.

2022 ESC/ERS

>20 mm Hg at rest

Current guideline threshold; Measured invasively.

Do not present the historical 25-mm Hg cutoff as the current standard.

Slide 5 · Pulmonary hypertension ≠ pulmonary arterial hypertension

PH describes a hemodynamic state; PAH is a specific disease group.

PH may arise from left heart disease, hypoxic lung disease, obstruction, or vascular arteriopathy.

PAH (group 1) primarily involves remodeling of the small pulmonary muscular arteries.

Etiologic classification is necessary before interpreting vascular findings or planning treatment.

Interpretation

Use “PH” for the umbrella diagnosis and “PAH” only when group 1 disease is established.

Slide 6 · Three independent drivers of elevated pressure

Driver

Immediate effect

Typical clinical context

Excess pulmonary flow

Greater flow through pulmonary bed

Certain congenital shunts

Elevated arterial resistance

Larger pressure drop across vascular bed

PAH; Obstructive lung disease; CTEPH

High downstream venous pressure

Back-transmission from left-sided circulation

Mitral disease; Left ventricular dysfunction

These are parallel mechanisms—not sequential stages.

Slide 7 · Hemodynamics localize the pressure source

Pattern

PAWP

Pulmonary vascular resistance

Pre-capillary PH

≤15 mm Hg

>2 Wood units

Isolated post-capillary PH

>15 mm Hg

≤2 Wood units

Combined post-/pre-capillary PH

>15 mm Hg

>2 Wood units

All patterns require mPAP >20 mm Hg at rest (2022 ESC/ERS).

Slide 8 · Five clinical groups: Mechanism and exemplar

Group

Primary mechanism

Representative condition

1 — PAH

Small pulmonary arterial disease

Idiopathic / heritable PAH; Systemic sclerosis

2 — Left heart

Back-transmitted venous pressure

Mitral stenosis; Heart failure

3 — Lung / hypoxia

Loss of vessels; Hypoxic injury

COPD; Interstitial lung disease

4 — Obstruction

Persistent thromboembolic obstruction

CTEPH

5 — Mixed / unclear

Multifactorial pathobiology

Heterogeneous disorders

CTEPH = chronic thromboembolic pulmonary hypertension.

Slide 9 · Group 1: Primary small-artery disease

PAH centers on pulmonary vascular cell dysfunction and remodeling.

Muscular arteries and arterioles develop medial hypertrophy and intimal fibrosis.

Progressive luminal compromise increases pulmonary vascular resistance.

Plexiform lesions may appear in advanced severe vascular disease.

Interpretation

Heritable and idiopathic PAH are prototypes, but group 1 includes several associated conditions.

Slide 10 · Group 2: Left-sided pressure transmits backward

Mechanistic sequence

Left-sided cardiac disease

Raised left atrial pressure

Pulmonary venous hypertension

Elevated pulmonary artery pressure

WHY IT MATTERS

A higher pulmonary artery pressure need not mean that primary arterial remodeling initiated the disease.

Slide 11 · Group 3: Lung injury increases resistance

Mechanistic sequence

Chronic parenchymal lung disease

Alveolar capillary bed loss

Higher vascular resistance

Pulmonary hypertension

WHY IT MATTERS

Hypoxia and associated vascular responses can add to the loss of functional cross-sectional area.

Slide 12 · Group 4: Unresolved thromboembolic obstruction

Mechanistic sequence

Prior pulmonary thromboembolism

Persistence / organization of thrombi

Functional vascular bed loss

Elevated pulmonary resistance

WHY IT MATTERS

Multiple small and recurrent emboli may gradually produce chronic PH.

Slide 13 · Group 5: Multifactorial mechanisms

Group 5 acknowledges PH that is not explained by one predominant pathway.

Obstruction, vascular remodeling, and altered flow can contribute simultaneously.

The category prevents incorrectly assigning every patient to a classic arteriopathy.

Interpretation requires integration of the underlying systemic disorder and hemodynamics.

Interpretation

Robbins groups such cases as unclear and/or multifactorial.

Slide 14 · Mechanism determines what pathology to seek

Suspected driver

Helpful clinical context

Expected tissue clue

Recurrent thromboemboli

Prior embolism or risk factors

Organizing / recanalized thrombi

Chronic hypoxic lung disease

Fibrosis, emphysema, chronic bronchitis

Capillary bed loss plus remodeled arteries

Left heart disease

Mitral or ventricular dysfunction

Changes secondary to venous pressure

Group 1 arteriopathy

Idiopathic / familial / associated PAH

Marked small-vessel remodeling

Patterns support an etiologic hypothesis; None is a standalone substitute for clinical correlation.

Slide 15 · Capillary loss converts structure into resistance

Mechanistic sequence

Fewer patent capillaries

Reduced vascular cross-sectional area

Resistance to forward flow increases

Right ventricular afterload rises

WHY IT MATTERS

Explains why diffuse lung disease can cause pulmonary vascular disease without a primary pulmonary arterial mutation.

Slide 16 · COPD: Vessel loss accompanies parenchymal injury

Severe emphysema and chronic bronchitis suggest group 3 PH.

Emphysematous destruction reduces available alveolar-capillary surface.

Chronic hypoxemia may accentuate pulmonary vascular resistance.

Morphology requires simultaneous assessment of airspaces, bronchi, and arteries.

Interpretation

Pulmonary vessel findings alone should not obscure the responsible lung phenotype.

Slide 17 · Interstitial fibrosis: Fewer functional capillaries

Interstitial disease creates a vascular as well as a gas-exchange lesion.

Architectural distortion and fibrosis destroy or compress capillary networks.

Less perfused vascular area elevates resistance as disease becomes extensive.

Pulmonary arterial remodeling may be secondary to chronic parenchymal disease.

Interpretation

Extensive fibrosis beside vascular remodeling shifts the etiologic inference toward group 3.

Slide 18 · Sleep apnea requires etiologic nuance

Obstructive sleep apnea, obesity, hypoxemia, and PH.

Sleep-related oxygenation abnormalities can coexist with clinically significant PH.

Current ESC/ERS guidance cautions that isolated nocturnal OSA alone generally does not cause PH.

Evaluate daytime hypoventilation, lung disease, obesity-related hypoventilation, and cardiac disease.

Interpretation

A source-era assertion is explicitly qualified by contemporary guidance.

Slide 19 · Mitral stenosis: Prototype post-capillary PH

A left atrial pressure barrier can elevate pulmonary arterial pressure.

The stenotic mitral valve increases left atrial pressure.

Increased pulmonary venous pressure is transmitted through the lung circulation.

Prolonged hemodynamic stress can produce secondary vascular changes.

Interpretation

Backward transmission of pressure is mechanistically distinct from primary PAH.

Slide 20 · Mitral stenosis: Causal chain

Mechanistic sequence

Impaired LV inflow

Raised left atrial pressure

Pulmonary venous hypertension

Raised pulmonary artery pressure

WHY IT MATTERS

This is a post-capillary mechanism and must not be mistaken for clinical group 1 PAH.

Slide 21 · Recurrent emboli: Chronic vascular obstruction

Repeated small emboli can be more important than one dramatic event.

Nonresolving thromboemboli reduce the perfused vascular bed.

Organization and recanalization may be observed histologically.

Persistent pulmonary resistance drives chronic right-heart load.

Interpretation

The burden of organized obstruction and the global hemodynamic context must be considered.

Slide 22 · Organized thrombus is an etiologic clue

A remodeled artery plus an organizing clot favors chronic thromboembolic disease.

Organizing thrombi become incorporated into vessel walls.

Recanalization creates channels through residual thrombotic material.

Numerous lesions across vessels strengthen suspicion for recurrent thromboemboli.

Interpretation

Do not mistake an organized thrombus for a plexiform endothelial proliferation.

Slide 23 · Systemic sclerosis: Connective-tissue association

Autoimmune disease can produce pulmonary vascular arteriopathy.

Systemic sclerosis as a notable associated cause of PH.

Pulmonary vascular involvement can increase resistance through arterial remodeling.

Coexisting interstitial disease is a competing or additional mechanism.

Interpretation

Distinguish vasculopathy-predominant PAH from PH dominated by fibrotic lung disease.

Slide 24 · Associated PAH: Context is essential

Certain infections and drug exposures can accompany group 1 PAH.

HIV infection and drug-associated cases among settings with severe arteriopathy.

Plexiform remodeling may occur in these clinical contexts.

A plexiform lesion signals a morphologic pattern, not a single unique cause.

Interpretation

Diagnostic attribution still depends on history and exclusion of competing hemodynamic mechanisms.

Slide 25 · Idiopathic PAH: Diagnosis after evaluation

“Idiopathic” is an etiologic designation rather than a morphologic subtype.

No recognized secondary cause is established after appropriate evaluation.

Some apparently sporadic cases have inherited molecular predisposition.

The term does not mean that molecular pathogenesis is absent.

Interpretation

Why investigation of familial disease informed pathogenesis.

Slide 26 · Familial PAH: Variable expression

Autosomal dominant inheritance can show strikingly incomplete penetrance.

A predisposition may segregate through relatives without clinical disease in every carrier.

Overt disease in only a minority of genetically susceptible relatives.

Genotype informs susceptibility; It does not guarantee clinical expression.

Interpretation

Avoid interpreting a normal phenotype in a relative as proof of absent genetic risk.

Slide 27 · BMPR2: Loss of a growth-regulatory brake

Mechanistic sequence

BMPR2 pathway perturbation

Disordered vascular cell regulation

Endothelial + smooth muscle proliferation

Remodeled obstructed arteries

WHY IT MATTERS

The simplified causal model reflects the Robbins text; It does not specify unverified intracellular intermediates.

Slide 28 · BMPR2 receptor: Biologic identity

BMPR2 is a receptor within the TGF-β superfamily.

Bone morphogenetic protein signaling helps regulate cell proliferation and differentiation.

The pathway also has roles in development and apoptosis.

Reduced BMPR2 signaling is linked to proliferative pulmonary vasculopathy.

Interpretation

Preserve distinction between a germline variant and reduced receptor expression in affected tissue.

Slide 29 · BMPR2 mutation frequencies: Source-era figures

Molecular findings in familial and apparently sporadic PAH.

Inactivating germline BMPR2 variants: About 75% of familial cases in its account.

About 25% of sporadic cases are described as harboring BMPR2 variants.

These are textbook-reported estimates, not universal current genetic-test yields.

Interpretation

Numerical estimates are presented with their original source context; Original chapter PDF unavailable.

Slide 30 · BMPR2 pathway may be altered without a variant

Normal DNA sequence does not imply normal pathway signaling.

Receptor downregulation in some idiopathic cases without BMPR2 mutations.

Other molecular defects can converge on the same pathway.

The common theme is dysregulated vascular cell behavior.

Interpretation

A negative BMPR2 test cannot exclude PAH.

Slide 31 · Two-hit model: Interacting susceptibility and triggers

Component

Proposed contribution

Clinical implication

BMPR2 predisposition

Loss of regulatory signaling

Carrier may remain unaffected

Modifier or environmental insult

Additional effect on vascular cell behavior

Risk and timing vary

Combined susceptibility

Permits proliferative vascular response

Remodeling may emerge

Conceptual model used to explain incomplete penetrance, not a proven universal sequence.

Slide 32 · Incomplete penetrance: Mechanistic implications

One genotype can produce several phenotypic outcomes.

Additional genetic modifiers or exposures may influence the transition to overt disease.

Timing and magnitude of vascular injury may vary among carriers.

A mechanistic model is not proof that every trigger has been identified.

Interpretation

Avoid deterministic counseling based solely on the presence of a BMPR2 variant.

Slide 33 · Cellular contributors to vascular remodeling

Compartment

Change emphasized by Robbins

Effect on vessel

Endothelium

Dysfunction and abnormal proliferation

Altered luminal architecture

Vascular smooth muscle

Hypertrophy / proliferation

Increased medial thickness

Intimal connective tissue

Fibrous expansion

Progressive luminal narrowing

Combined remodeling raises resistance throughout affected small vessels.

Slide 34 · Positive feedback: Pressure and remodeling

Mechanistic sequence

Increased vascular resistance

Higher pulmonary arterial pressure

Ongoing wall stress / injury

Further vessel remodeling

WHY IT MATTERS

Conceptual clinicopathologic model: Structural narrowing can sustain hemodynamic disease.

Slide 35 · Morphology spans the pulmonary arterial tree

Pulmonary hypertension is not restricted to the smallest vessels.

Large main or branch pulmonary arteries may show marked wall changes.

The most diagnostic microscopic remodeling lies in small arteries and arterioles.

Both lesion distribution and background lung pathology contribute to etiology.

Interpretation

Changes extending from main pulmonary arteries to small arterioles.

Slide 36 · Small-vessel morphology: Reference architecture

Schematic cross-section (not a clinical specimen)

Pulmonary muscular artery

Baseline wall-to-lumen relationship

Muscular artery with distinct lumen and muscular wall.

Illustration intentionally simplifies vessel layers.

Compare subsequent slides at the same illustrative scale.

Slide 37 · Medial hypertrophy narrows the effective lumen

Schematic cross-section (not a clinical specimen)

Pulmonary muscular artery

Expanded media

Pulmonary muscular arteries develop conspicuously thickened media.

Smooth-muscle expansion occupies more of the wall profile.

The net consequence is a higher-resistance vascular segment.

Slide 38 · Intimal fibrosis may leave a pinpoint lumen

Schematic cross-section (not a clinical specimen)

Pulmonary muscular artery

Severe fibrous luminal compromise

Intimal collagenous expansion compounds medial thickening.

The 40–300 μm small-artery/arteriole range.

Severe narrowing can reduce the lumen to a narrow residual channel.

Slide 39 · Plexiform lesion: Complex endothelial channels

Schematic cross-section (not a clinical specimen)

Affected small artery

Tuft of capillary-like channels

A tuft of capillary-like channels forms within / near a remodeled small artery.

The network may bridge a dilated thin-walled arterial lumen.

This is a schematic of advanced arteriopathy—not a photomicrograph.

Slide 40 · Patterns: Medial, intimal, plexiform

Lesion

Dominant tissue alteration

Practical recognition

Medial hypertrophy

Expanded smooth-muscle layer

Thick arterial media

Intimal fibrosis

Concentric fibrous luminal encroachment

Small residual opening

Plexiform lesion

Disordered capillary-like channels

Tuft / web-like vascular complex

These are associated changes, not three obligatory chronological stages.

Slide 41 · Plexiform lesions: Settings and specificity

Plexiform remodeling is characteristic of severe vascular disease but is not pathognomonic.

It is conspicuous in idiopathic and heritable group 1 PAH.

Robbins also associates it with unrepaired shunt-related disease, HIV, and drugs.

Clinical classification of congenital-heart-associated PH requires modern hemodynamic context.

Interpretation

The source’s group attribution for congenital shunts is not reproduced uncritically.

Slide 42 · Large artery change differs from systemic atherosclerosis

Atheroma-like lesions may occur in the pulmonary artery and major branches.

Large arteries can show wall thickening and plaque-like remodeling.

The source cautions that classic systemic atherosclerosis is not the universal pattern.

Small muscular arterial hypertrophy and intimal fibrosis are more prominent lesions.

Interpretation

Avoid equating pulmonary vascular remodeling with ordinary coronary atherosclerosis.

Slide 43 · Morphology provides clues about cause

Observed accompanying finding

Etiologic inference

Interpretative caution

Recanalized / organized thrombi

Prior recurrent embolic disease

Requires correlation with vascular imaging

Extensive lung fibrosis

Chronic interstitial lung disease

More than one PH mechanism may coexist

Severe emphysema + bronchitis

Chronic hypoxic parenchymal disease

Pressure severity not inferred from image alone

Plexiform arteriopathy

Severe pulmonary arteriopathy

Not etiology-specific by itself

Look beyond the artery: Assess the accompanying lung and heart findings.

Slide 44 · Right ventricular hypertrophy is the cardiac counterpart

The right ventricle adapts to chronically increased afterload.

Increased pulmonary vascular resistance raises right ventricular pressure work.

The right ventricular myocardium hypertrophies during compensation.

Progressive decompensation produces chronic cor pulmonale.

Interpretation

The heart and pulmonary vessels reflect the same sustained hemodynamic load.

Slide 45 · From arteriopathy to cor pulmonale

Mechanistic sequence

Small-vessel luminal narrowing

Elevated pulmonary vascular resistance

Right ventricular hypertrophy

Right ventricular failure

WHY IT MATTERS

Morphology creates hemodynamic afterload; Prolonged afterload ultimately threatens pump function.

Slide 46 · Clinical silence may conceal advanced pathology

Symptoms often appear only after significant vascular and right-heart impairment.

The pulmonary vascular bed can lose functional reserve progressively.

Non-specific exertional symptoms may delay recognition.

Severity cannot be reliably inferred from symptom description alone.

Interpretation

Clinical and hemodynamic evaluations are complementary; Do not diagnose PH from symptoms alone.

Slide 47 · Dyspnea: Impaired cardiopulmonary reserve

Breathlessness is a major presenting symptom in idiopathic PAH.

A high-resistance circuit limits the ability to augment pulmonary blood flow.

Exercise accentuates the mismatch between demand and cardiac output reserve.

Dyspnea is non-specific; Competing pulmonary and cardiac causes remain possible.

Interpretation

Relate the symptom to circulatory reserve rather than assuming a primary airway obstruction.

Slide 48 · Fatigue: Inadequate forward-flow reserve

Reduced functional cardiac output helps explain early exertional fatigue.

The right ventricle may fail to maintain flow at increased exertion.

Patients can report functional limitation before overt resting failure.

The symptom has low specificity and requires a hemodynamic differential.

Interpretation

Exertional intolerance is compatible with PH but is not diagnostic.

Slide 49 · Chest discomfort and angina-like pain

Pulmonary hypertension may produce chest pain without coronary plaque rupture.

An anginal character of pain in some idiopathic cases.

Increased ventricular pressure work is a plausible contributor.

Cardiac ischemia and other urgent causes still require evaluation.

Interpretation

Do not label a real chest pain episode as benign on the basis of presumed PH.

Slide 50 · Cyanosis and right-heart failure are late warnings

Severe disease progresses beyond exertional symptoms.

Respiratory distress and cyanosis in advanced disease.

Right ventricular hypertrophy eventually may progress to pump failure.

Clinical decompensation reflects severe integrated cardiopulmonary dysfunction.

Interpretation

Advanced signs should prompt timely specialist assessment.

Slide 51 · Cor pulmonale: Structural and functional endpoint

Chronic lung or pulmonary vascular disease can lead to right-heart remodeling.

Sustained pulmonary afterload produces right ventricular hypertrophy.

Reduced cardiac output and systemic venous congestion may follow decompensation.

Identify whether the driving process is vascular, parenchymal, or thromboembolic.

Interpretation

Cor pulmonale is a consequence, not a separate etiologic PH group.

Slide 52 · Intercurrent disease can precipitate deterioration

Severely compromised right-heart reserve is sensitive to added insults.

Robbins mentions superimposed thromboembolism and pneumonia during deterioration.

Further vascular obstruction can abruptly increase afterload.

Acute infection may impair oxygenation and destabilize hemodynamics.

Interpretation

Historical source descriptions of untreated survival are not treated as present-day prognosis.

Slide 53 · Histologic appearance versus mechanism

Appearance

Mechanistic interpretation

What to verify clinically

Thick media

Chronic arterial muscular response

Right-heart load / PH context

Concentric intimal fibrosis

Reduced vessel lumen

Distribution and background disease

Plexiform complex

Severe endothelial remodeling

PAH-associated conditions

Recanalized thrombus

Chronic organized obstruction

Thromboembolic workup

Histology alone does not classify pulmonary hypertension.

Slide 54 · Case: Systemic sclerosis with dyspnea

A patient with systemic sclerosis develops progressive exertional dyspnea. Pulmonary vascular remodeling is suspected.

Discussion prompts

Could pulmonary vasculopathy be sufficient to explain PH?

What competing structural lung mechanism must be sought?

Which tests would identify the dominant hemodynamic driver?

Facilitator note: Answer and rationale are in PowerPoint speaker notes.

Slide 55 · Case: Recurrent small pulmonary emboli

A patient has repeated pulmonary embolic episodes and progressive exertional limitation. Histology shows organized material with channels.

Discussion prompts

What does recanalization indicate?

How can recurrent small thrombi elevate resistance?

Which clinical group should be investigated?

Facilitator note: Answer and rationale are in PowerPoint speaker notes.

Slide 56 · Case: Asymptomatic BMPR2 variant carrier

A relative of a patient with heritable PAH carries a pathogenic BMPR2 variant but has no symptoms.

Discussion prompts

Does a variant guarantee clinically manifest disease?

Which pathogenetic concept explains discordant relatives?

Why is “idiopathic” not synonymous with “non-genetic”?

Facilitator note: Answer and rationale are in PowerPoint speaker notes.

Slide 57 · Diagnostic pathway: Screen, detect, confirm

Mechanistic sequence

Clinical suspicion

Echocardiography assessment

Referral when appropriate

Right-heart catheterization

WHY IT MATTERS

The 2022 ESC/ERS diagnostic pathway requires invasive hemodynamic confirmation; Echo alone cannot definitively classify PH.

Slide 58 · Right-heart catheterization defines the phenotype

Catheterization integrates pressure measurements and flow.

Mean pulmonary arterial pressure establishes whether hemodynamic PH is present.

Wedge pressure distinguishes elevated left-sided filling pressure from pre-capillary patterns.

Cardiac output is used to calculate pulmonary vascular resistance.

Interpretation

Current 2022 ESC/ERS threshold: MPAP >20 mm Hg; Do not diagnose PAH on mPAP alone.

Slide 59 · Pressure phenotype directs the differential

Hemodynamics

Initial etiologic direction

Why

Elevated PAWP

Left-heart disease evaluation

Venous pressure can transmit upstream

High PVR + normal PAWP

PAH, lung disease, CTEPH evaluation

Resistance lies predominantly before capillaries

Combined elevation

Mixed post- and pre-capillary process

Chronic venous pressure may coexist with vascular remodeling

These are organizing heuristics; The complete diagnosis requires clinical context.

Slide 60 · Management is cause-directed

A pathology diagnosis is useful when it identifies the driving pathway.

Secondary PH requires treatment of the precipitating disorder where possible.

Hypoxemia and chronic thromboembolic disease require different assessments.

PAH-directed vasodilator therapy is selected within the appropriate clinical group.

Interpretation

Treating the underlying trigger and specialized care for group 1.

Slide 61 · Why PAH drugs do not fit every PH group

An elevated pressure is not, by itself, a mechanism-specific treatment indication.

Group 2 is dominated by elevated left-sided filling pressure.

Group 3 is often dominated by chronic lung injury and hypoxic physiology.

Group 4 includes potentially addressable organized arterial obstruction.

Interpretation

Avoid indiscriminate treatment transfer between PH groups; Therapeutic details require specialist guideline review.

Slide 62 · Lung transplantation in selected advanced disease

Robbins recognizes transplantation as definitive treatment for selected patients.

Advanced progressive pulmonary vascular injury may be difficult to reverse.

Clinical candidacy depends on disease phenotype, comorbidities, and severity.

Transplantation is a highly selected option rather than routine management.

Interpretation

The textbook gives no universal eligibility criteria; None are invented here.

Slide 63 · High-yield differential: Vessel versus parenchyma

Primary clue

Prefer this mechanism

Do not overlook

Small arteries remodeled; Background lung relatively preserved

Pulmonary arteriopathy

Cardiac, thromboembolic, or inherited causes

Severe emphysema or fibrosis

Capillary bed loss / hypoxia

Coexisting pulmonary arteriopathy

Organized recanalized thrombi

Chronic thromboembolic obstruction

Secondary adaptive hypertrophy

Raised left atrial pressure

Post-capillary PH

Combined pre-capillary component

The final classification is etiologic and hemodynamic, not microscopic alone.

Slide 64 · Diagnostic pitfalls that change classification

Four errors can produce a convincing but wrong pulmonary hypertension diagnosis.

Equating elevated pulmonary artery pressure with group 1 PAH.

Using ≥25 mm Hg as though it remains the current guideline threshold.

Treating plexiform remodeling as pathognomonic for idiopathic disease.

Ignoring left-heart disease, chronic lung disease, or thromboemboli.

Interpretation

Correct classification integrates pressures, structural disease, clinical risk factors, and pathology.

Slide 65 · Synthesis: Five causal anchors

Anchor

Core mechanism

Signature correlation

Pressure

Resistance, flow, or venous back pressure

Measure and phenotype hemodynamics

Etiology

Five broad clinical groups

Identify the predominant driver

Molecular

BMPR2 pathway / modifiers

Variable inherited susceptibility

Morphology

Medial + intimal + plexiform changes

Reduced small-vessel caliber

Clinical

Chronic right ventricular afterload

Cor pulmonale / right-heart failure

Use these anchors to explain why the findings occur—not only to memorize them.

Slide 66 · Application question: Interpret a narrowed arteriole

A small pulmonary artery has severe medial hypertrophy and intimal fibrosis. The patient also has extensive pulmonary fibrosis.

Discussion prompts

Does the artery alone establish idiopathic PAH?

Which group becomes plausible from the lung background?

What confirms hemodynamic pulmonary hypertension?

Facilitator note: Answer and rationale are in PowerPoint speaker notes.

Slide 67 · Selected references

Core textbook and separately verified guideline

Robbins, Cotran & Kumar. Pathologic Basis of Disease. 11th ed. Elsevier; 2026. Chapter 15, “The Lung,” pp. 640–642.

Humbert M, et al. 2022 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension. Eur Heart J. 2022;43:3618–3731. doi:10.1093/eurheartj/ehac237.