Q-Bank Breakdown: Pulmonary hypertension — Why Every Answer Choice Matters

Pulmonary hypertension (PH) is one of those Step questions where the vignette feels like “dyspnea + loud P2 = pick the pulmonary answer,” but the test writers are really checking whether you can classify PH, predict hemodynamics, and anticipate which therapies help (or hurt). The highest-yield move is to treat every answer choice like it’s a mini-lesson—because on exam day, the distractors are often yesterday’s missed question.

Tag: Pulmonary > Pulmonary Vascular & Critical Care

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The Q-bank vignette (classic setup)

A 34-year-old woman presents with progressive exertional dyspnea and fatigue for 8 months. She has near-syncope when climbing stairs. No history of smoking. Vitals: BP 108/68, HR 96. Exam: loud P2, parasternal heave, JVP elevated, and mild ankle edema. Lungs are clear. ECG shows right axis deviation and RV strain. Echocardiogram suggests elevated pulmonary artery systolic pressure with RV dilation; LV function is normal. Right-heart catheterization:

• Mean pulmonary artery pressure (mPAP): 35 mmHg
• Pulmonary capillary wedge pressure (PCWP): 10 mmHg
• Cardiac output (CO): 3.5 L/min
• Pulmonary vascular resistance (PVR): elevated

Question: Which is the most likely underlying mechanism (and best next step)?

Answer choices

A. Hyperplasia of pulmonary smooth muscle due to idiopathic pulmonary arterial hypertension (PAH)
B. Chronic thromboembolic occlusion of pulmonary arteries
C. LV diastolic dysfunction causing pulmonary venous hypertension
D. Hypoxic vasoconstriction from COPD
E. Alveolar hemorrhage from granulomatosis with polyangiitis

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Step 1/2 anchor: What the cath data is screaming

This is precapillary pulmonary hypertension:

• PH definition (high-yield): mPAP > 20 mmHg at rest (modern definition; many question banks still use ≥25)
• Precapillary PH: PCWP ≤ 15 mmHg with elevated PVR
• Postcapillary PH (left heart disease): PCWP > 15 mmHg

Here:

• mPAP high (35)
• PCWP normal (10) → not left-sided congestion
• PVR elevated → problem is in the pulmonary arterioles/arteries

That combination pushes you toward Group 1 PAH or Group 4 CTEPH, and away from left heart failure (Group 2).

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Correct answer: A. Idiopathic PAH (Group 1) with pulmonary arteriolar remodeling

Why A is correct

Idiopathic PAH is a precapillary PH due to endothelial dysfunction and vascular remodeling of small pulmonary arteries/arterioles:

Pathophysiology you should know cold

• ↑ Endothelin (vasoconstrictor, pro-proliferative)
• ↓ Nitric oxide and ↓ prostacyclin (normally vasodilatory)
• Smooth muscle hypertrophy, intimal fibrosis, and plexiform lesions (buzzword)
• Can be associated with BMPR2 mutation (TGF-β signaling pathway) → increased vascular smooth muscle proliferation

Clinical clues

• Young woman with progressive exertional dyspnea, near-syncope
• Loud P2, parasternal heave, signs of RV failure
• Clear lungs (often in PAH; no primary parenchymal process)

Best next step (commonly tested)

After confirming PAH physiology on right-heart cath, management depends on severity and vasoreactivity testing:

• Vasoreactivity testing during cath (e.g., inhaled NO, IV epoprostenol)
  • If positive: high-dose calcium channel blockers (e.g., amlodipine, nifedipine, diltiazem)
• If not vasoreactive or more advanced disease:
  • Endothelin receptor antagonists: bosentan, ambrisentan, macitentan
  • PDE-5 inhibitors: sildenafil, tadalafil
  • Prostacyclin analogs / agonists: epoprostenol, treprostinil, iloprost; selexipag
• Supportive: diuretics for RV congestion, oxygen if hypoxemic, supervised exercise, pregnancy avoidance counseling

Must-know contraindication: Many PAH drugs (notably endothelin receptor antagonists) are teratogenic.

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Why each distractor is wrong (and what it was trying to teach)

B. Chronic thromboembolic pulmonary hypertension (CTEPH) — tempting, but missing key clues

CTEPH = Group 4 PH from chronic organized thrombi obstructing pulmonary arteries.

When you should pick CTEPH

• History of prior PE/DVT, thrombophilia, malignancy, indwelling catheters
• Persistent dyspnea after PE
• Mismatched perfusion defects on V/Q scan (screening test)

Hemodynamics

• Also precapillary: mPAP ↑, PCWP normal, PVR ↑
  So why not B here? The vignette lacks thromboembolic risk factors, and Q-banks often explicitly hint at PE history if they want CTEPH.

High-yield management

• Lifelong anticoagulation (if no contraindication)
• Pulmonary thromboendarterectomy can be curative
• Balloon pulmonary angioplasty in select cases
• Riociguat (sGC stimulator) for inoperable or residual disease (commonly tested)

Exam pearl: If the stem says “PH + prior PE + V/Q mismatch,” think CTEPH before idiopathic PAH.

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C. LV diastolic dysfunction → pulmonary venous HTN (Group 2) — the wedge pressure would be high

This choice is postcapillary PH due to left heart disease (systolic or diastolic failure, valvular disease).

What you’d expect

• PCWP > 15 mmHg (key discriminator)
• Often signs of left-sided congestion: orthopnea, PND, crackles, S3 (not always), LA enlargement
• Echo: LV hypertrophy or dysfunction, valvular disease

Why it’s wrong here

• PCWP is 10 mmHg (normal), LV function is normal, lungs are clear.

High-yield caution: PAH-specific vasodilators can worsen symptoms in Group 2 PH by increasing pulmonary blood flow into an already congested left atrium/ventricle → pulmonary edema.

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D. Hypoxic vasoconstriction from COPD (Group 3) — would usually have lung findings and hypoxemia

Group 3 PH comes from chronic lung disease and/or hypoxemia (COPD, ILD, OSA).

Mechanism

• Alveolar hypoxia triggers hypoxic pulmonary vasoconstriction → vascular remodeling over time

Clues you’d expect

• Smoking history, wheezing, prolonged expiration (COPD) or inspiratory crackles (ILD)
• Chronic hypoxemia, polycythemia
• Abnormal PFTs and imaging

Why it’s wrong here

• Young nonsmoker, clear lungs, no COPD symptoms.
• The vignette is “clean” and centered on pulmonary vascular disease rather than parenchymal lung disease.

High-yield fact: The best treatment in Group 3 is addressing the underlying lung disease and giving supplemental oxygen (oxygen reduces hypoxic vasoconstriction).

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E. Alveolar hemorrhage from GPA — wrong phenotype (this is not a PH presentation)

Granulomatosis with polyangiitis can cause:

• Upper airway disease (sinusitis, otitis)
• Lung nodules/cavitations, hemoptysis
• Rapidly progressive glomerulonephritis

Diffuse alveolar hemorrhage presents with:

• Hemoptysis (sometimes absent), anemia
• Diffuse alveolar infiltrates
• Hypoxemic respiratory failure

Why it’s wrong here

• No hemoptysis, no diffuse infiltrates, no systemic vasculitis clues.
• Also not the typical mechanism for chronic, progressive pulmonary hypertension.

Board-style reminder: Hemoptysis + pulmonary-renal syndrome = think ANCA vasculitis or anti-GBM. Progressive dyspnea + loud P2 + clear lungs = think PH.

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Rapid classification table (high-yield)

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The 3 hemodynamic patterns you must recognize

You’ll often be given mPAP, PCWP, CO; if PVR isn’t given, you should infer it.

• Precapillary PH (Groups 1, 3, 4, some 5):
  • mPAP ↑, PCWP normal, PVR ↑, CO often ↓ later
• Postcapillary PH (Group 2):
  • mPAP ↑, PCWP ↑
  • PVR may be normal early; can increase with chronic remodeling (“combined post- and precapillary PH”)
• High-output states (some Group 5):
  • mPAP ↑, CO ↑, PVR may be normal/low depending on cause

Formula (occasionally tested):
$PVR = \frac{mPAP - PCWP}{CO}$
(Unit conversions vary; Q-banks typically care about directionality.)

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Micro–question bank takeaways (what to memorize)

• Loud P2 + parasternal heave + clear lungs → pulmonary vascular disease until proven otherwise.
• PCWP is the splitter: normal wedge = not left-heart disease.
• Idiopathic PAH: BMPR2, plexiform lesions, ↑ endothelin, ↓ NO/prostacyclin.
• CTEPH clue = V/Q mismatch and history/risk of PE; treat with thromboendarterectomy when possible.
• Group 3 PH: treat hypoxia with oxygen; don’t overthink PAH meds as first-line.
• Group 2 PH: treat the left heart; PAH vasodilators can backfire.