Mean pulmonary artery pressure >20 mmHg at rest; 5 WHO groups by etiology.
Also known as: pulmonary hypertension, PH, PAH, pulmonary arterial hypertension, cor pulmonale
Overview
Resting mean pulmonary artery pressure (mPAP) >20 mmHg measured by right heart catheterization (lowered from the prior >25 mmHg threshold by the 2018 World Symposium). Classified into 5 WHO groups by mechanism.
Epidemiology
PAH (Group 1) is rare: ~15-50 cases per million. Idiopathic PAH is most common in women aged 30-50. Group 2 (left heart disease) and Group 3 (lung disease) account for the vast majority of all pulmonary hypertension cases.
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Question 1PulmonaryMedium
A 45-year-old male has a 3-year history of progressive dyspnea on exertion and lower extremity edema. He has no cardiac history, no anorexigen use, and a negative connective-tissue disease and HIV workup. Echo shows right ventricular enlargement with D-shaped septum, estimated right ventricular systolic pressure (RVSP) 68 mmHg, and normal left-sided pressures. Right heart catheterization: mean pulmonary artery pressure (mPAP) 42 mmHg, pulmonary capillary wedge pressure (PCWP) 9 mmHg, pulmonary vascular resistance (PVR) 8 Wood units, cardiac index (CI) 1.9 L/min/m². Ventilation-perfusion (V/Q) scan is normal. Vasodilator testing shows no response to inhaled nitric oxide. Which of the following is the most likely diagnosis?
ACOPD with cor pulmonale
BChronic thromboembolic pulmonary hypertension
CPulmonary hypertension due to HFpEF
DIdiopathic pulmonary arterial hypertension
EPortopulmonary hypertension
Reveal answer & full explanation
Correct answer: D — Idiopathic pulmonary arterial hypertension
ACOPD with cor pulmonale
BChronic thromboembolic pulmonary hypertension
CPulmonary hypertension due to HFpEF
DIdiopathic pulmonary arterial hypertension✓
EPortopulmonary hypertension
Why Idiopathic pulmonary arterial hypertension is correct
Idiopathic pulmonary arterial hypertension (PAH) (Group 1) is a diagnosis of exclusion, and every secondary cause here has been ruled out
Normal ventilation-perfusion (V/Q) scan excludes chronic thromboembolic disease, and a negative connective-tissue, HIV, and anorexigen history excludes associated (Group 1 secondary) causes
Vasodilator testing with inhaled nitric oxide showed no response, ruling out calcium channel blocker candidacy
Low cardiac index (CI) of 1.9 L/min/m² indicates high-risk PAH
Why the others are wrong
COPD with cor pulmonale — no history of obstructive lung disease; COPD-related PH typically causes only mild-to-moderate mPAP elevation, not 42 mmHg (right-concept-wrong-setting)
Portopulmonary hypertension — this Group 1 subtype requires underlying portal hypertension or chronic liver disease, and no cirrhosis, ascites, or varices are described (right-concept-wrong-etiology)
Chronic thromboembolic pulmonary hypertension — the normal V/Q scan and absent thromboembolic history exclude organized clot, which is the screening test that must be negative before calling PAH idiopathic (anchoring on precapillary PH without excluding CTEPH)
Pulmonary hypertension due to HFpEF — left heart disease (Group 2 PH) is the most common cause of PH and can present with dyspnea, edema, and RV enlargement, but it is postcapillary with PCWP above 15 mmHg; a PCWP of 9 mmHg with PVR 8 Wood units defines precapillary PH (anchoring on the most common cause of PH)
Additional high-yield points
Positive vasodilator response is defined as an mPAP fall of at least 10 mmHg to an absolute value of 40 mmHg or less, with increased or unchanged cardiac output (CO) — those responders may use calcium channel blockers
WHO functional class guides treatment intensity
Initial combination therapy: the AMBITION trial showed ambrisentan plus tadalafil superior to monotherapy in WHO functional class (FC) II–III patients
High-risk PAH: add IV or SC prostacyclin (epoprostenol or treprostinil)
Balloon atrial septostomy is palliative for severe refractory PAH
Lung transplant is reserved for patients failing maximal medical therapy
Question 2PulmonaryMedium
A 41-year-old woman with no prior medical history has exertional dyspnea, a loud P2, and echocardiographic evidence of elevated pulmonary artery pressures with normal left ventricular function and valves. Pulmonary function tests and a ventilation-perfusion scan are normal. Which of the following best explains the vascular change?
AChronic left-sided elevation of filling pressure
BHypoxic vasoconstriction from chronic lung disease
CPulmonary arteriolar remodeling with constriction
DGranulomatous vascular infiltration from sarcoidosis
Why Pulmonary arteriolar remodeling with constriction is correct
Idiopathic pulmonary arterial hypertension in a young woman reflects intrinsic arteriolar vasoconstriction, smooth-muscle proliferation, and remodeling that raise pulmonary vascular resistance.
A loud P2 signals high pulmonary artery pressure transmitted to the pulmonic valve.
Progressive resistance imposes right ventricular pressure load and eventual strain.
Why the others are wrong
Chronic left-sided elevation of filling pressure — Group 2 pulmonary hypertension is driven by left heart disease, but nothing here suggests left ventricular failure or valve disease; this is the postcapillary-vs-precapillary trap.
Recurrent chronic thromboembolic vascular obstruction — Chronic thromboembolic disease causes pulmonary hypertension through clot burden, which her normal ventilation-perfusion scan argues against; this is the embolic-cause trap.
Hypoxic vasoconstriction from chronic lung disease — Group 3 disease requires underlying COPD or interstitial lung disease, which this patient lacks; this is the hypoxia-driven trap.
Granulomatous vascular infiltration from sarcoidosis — sarcoidosis often affects women in this age range and can cause group 5 pulmonary hypertension through granulomatous vessel involvement, fibrosis, or nodal compression, but nothing here suggests hilar adenopathy or multisystem disease; this is the demographic-anchoring trap.
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WHO classification of pulmonary hypertension (5 groups) — guides workup and treatment.
Treatment
First-line
Treat the underlying cause first: heart failure (Group 2), chronic lung disease (Group 3), CTEPH (Group 4), connective tissue or other (Group 5)
PAH-specific therapies are reserved for Group 1 and CTEPH inoperable patients — they can WORSEN Groups 2 and 3 (exception: inhaled treprostinil is approved for PH due to ILD)
Group 1 PAH general measures: supplemental O2 if hypoxemic, diuretics for RV volume overload, no routine anticoagulation (not generally recommended in PAH; individualize), avoid pregnancy
Non-vasoreactive (most), by risk (ESC/ERS 2022): low or intermediate risk starts dual oral therapy with an ERA plus a PDE5i (e.g., ambrisentan + tadalafil, AMBITION trial); high risk starts triple therapy that adds IV/SC prostacyclin; patients with cardiopulmonary comorbidities start with monotherapy (PDE5i or ERA). Pathways:
Inadequate response on dual oral therapy at follow-up: intermediate-low risk, add selexipag or switch the PDE5i to riociguat; intermediate-high or high risk, add IV/SC prostacyclin (IV epoprostenol has the strongest evidence, including survival benefit) and refer for lung transplant evaluation
Activin signaling inhibitor sotatercept (STELLAR 2023) — added benefit on top of background therapy
CTEPH (Group 4): lifelong therapeutic anticoagulation for all; pulmonary endarterectomy (potentially curative) for surgical candidates; riociguat for inoperable; balloon pulmonary angioplasty in select centers
Refractory PAH: lung or heart-lung transplantation, atrial septostomy as bridge
Group 3 PH from lung disease: inhaled treprostinil approved (INCREASE trial) for PH-ILD; otherwise treat underlying disease and optimize oxygen
Maternal mortality in PAH remains high (~12-20% in contemporary series; 30-50% historically) — pregnancy contraindicated
PANCE pearls
Treatment of Group 1 PAH with PAH-specific drugs can WORSEN Groups 2 (left heart) and 3 (lung disease) — always classify before treating.
V/Q scan, not CTPA, is the screening test for CTEPH — sensitivity for chronic emboli is higher.
Right heart catheterization is required to confirm PAH and guide therapy; echo estimates can over- or underestimate by 20 mmHg.
Pregnancy in PAH carries high maternal mortality (~12-20% in contemporary series; 30-50% historically) — discuss avoidance/termination and effective contraception (no estrogen).
Bosentan carries a boxed warning for hepatotoxicity (monthly LFTs; restricted REMS program) and, like all ERAs, for embryo-fetal toxicity: contraindicated in pregnancy, so exclude pregnancy before starting and use effective contraception (the ERA embryo-fetal toxicity REMS requirements were removed in 2025).
References
ESC/ERS 2022 — 2022 ESC/ERS Guidelines for the Diagnosis and Treatment of Pulmonary Hypertension (Humbert et al., Eur Heart J 2022)
AMBITION Trial — Initial Use of Ambrisentan plus Tadalafil in Pulmonary Arterial Hypertension (Galiè et al., NEJM 2015)
STELLAR Trial — Phase 3 Trial of Sotatercept for Treatment of Pulmonary Arterial Hypertension (Hoeper et al., NEJM 2023;388:1478-1490)
INCREASE Trial — Inhaled Treprostinil in Pulmonary Hypertension Due to Interstitial Lung Disease (Waxman et al., NEJM 2021)
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