Cor Pulmonale

Meet the patient

A 68-year-old man with 50 pack-years of smoking and known GOLD stage 3 COPD lands in clinic with three months of ankle swelling, a shirt-collar tightness, and dyspnoea walking to the bathroom. His JVP sits at 6 cm with a flicking v wave, his apex is undisplaced, and a loud P2 with a parasternal heave greet your palm at the left sternal edge.[1]

The trap he sets for the unwary registrar is the one this whole chapter turns on: is this left-heart failure or cor pulmonale? His lungs are the cause, his left heart is normal — and the next two hours of management fork on that single distinction.[1]

The heart fails because the lung is sick — not the other way round

Cor pulmonale is right-heart failure from lung disease, with a normal left heart — the lung is the cause, the right ventricle is the casualty. The WHO (1963) definition still frames the exam answer: "hypertrophy of the right ventricle resulting from diseases affecting the function and/or structure of the lung, except when these alterations are the result of diseases that primarily affect the left side of the heart."[1]

The mechanism is two-headed — chronic alveolar hypoxia-driven pulmonary vasoconstriction plus loss of the pulmonary vascular bed — and both raise pulmonary vascular resistance (PVR) until the thin-walled RV hypertrophies, then dilates, then fails.[1]

Etymology for viva gold: cor pulmonale is straight Latin — cor, heart, plus pulmo, lung — literally "the lung-heart". The name carries the diagnosis in two syllables: if the lung is not the cause, it is not cor pulmonale.[1]

In the current WHO clinical classification of pulmonary hypertension, cor pulmonale sits in Group 3 — pulmonary hypertension due to lung disease and/or hypoxia.[1]

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Three clinically distinct flavours share the name — separate them at the door:[1]

• Acute cor pulmonale — sudden RV pressure overload, classically a massive pulmonary embolism (or ARDS); the RV acutely dilates and fails. A different entity, managed as acute PE.
• Chronic cor pulmonale — the progressive, exam-favourite form; insidious in advanced COPD, ILD, OSA/OHS, CTEPH, or kyphoscoliosis. The rest of this chapter is about this one.
• Compensated vs decompensated — compensated is RV hypertrophy without systemic congestion; decompensated is overt RV failure with raised JVP, oedema and hepatomegaly.[1]

PH vs cor pulmonale — the haemodynamic anchor

Pulmonary hypertension is a number; cor pulmonale is a structural RV change. They are not the same thing. The 2022 ESC/ERS Guidelines lowered the diagnostic threshold and introduced a PVR cut-off:[1]

• PH is present when mean pulmonary artery pressure (mPAP) is over 20 mmHg at rest (previously over 25 mmHg).
• Pre-capillary PH (the form that causes cor pulmonale) — mPAP over 20 mmHg, pulmonary capillary wedge pressure (PCWP) under 15 mmHg, PVR over 2 Wood units.
• Isolated post-capillary PH (left-heart disease) — mPAP over 20 mmHg, PCWP over 15 mmHg, PVR under 2 WU.[1]

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The five WHO groups — and the curable one hiding in Group 4

Every PH patient must be placed in the correct group, because treatment is group-specific — and one group is surgically curable. Cor pulmonale inherits the five WHO groups of PH; the causes that produce it cluster in Group 3, but a surgically curable cause hides in Group 4 (CTEPH) and must be excluded in every case.[1]

WHO Group 3 (lung disease / hypoxia) — the cor-pulmonale causes

The lung-disease causes group cleanly by mechanism:[1]

[1]

The complete WHO 5-group classification of pulmonary hypertension

The 2022 ESC/ERS Guidelines sort PH into five clinical groups by mechanism. Cor pulmonale is, by definition, the structural RV consequence of any pre-capillary group (1, 3, 4, 5), but the term is used most strictly for Group 3.[1]

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How common, and who lands on the ward with it

COPD is the prototype substrate, and the prevalence of PH climbs with every GOLD stage. A few facts worth carrying into the viva:[1]

• Cor pulmonale complicates a significant proportion of advanced COPD; PH prevalence rises with GOLD stage, reaching a majority of patients with very severe (GOLD 4) disease.
• In interstitial lung disease (especially IPF), PH develops in a large fraction of advanced cases and is a major cause of death.
• Obesity hypoventilation syndrome (OHS) is almost always accompanied by some degree of PH, and rising obesity has made this an increasingly common cause.
• Chronic thromboembolic PH (CTEPH) complicates roughly 0.1–9% of acute PE survivors within 2 years; it is under-diagnosed because it is missed without a V/Q scan.[1]

The principal risk factors are the same list read backwards: heavy smoking (for COPD), longstanding COPD with chronic hypoxaemia, severe ILD (IPF), morbid obesity, uncontrolled OSA, recurrent PE or prior DVT, high-altitude dwelling, kyphoscoliosis, neuromuscular disease, occupational dust/fume exposure.[1]

The examiner's favourite physiology question: why does chronic hypoxia produce cor pulmonale? Because sustained alveolar hypoxia (PaO2 under 55 mmHg) produces diffuse hypoxic pulmonary vasoconstriction, which — combined with loss of the capillary bed — chronically raises PVR, loads the RV, and is partly reversible when the hypoxia is corrected by LTOT.[1][2]

The mechanism — three stages, one vicious cycle

The mechanism runs in three stages — (A) the rise in PVR, (B) the RV response, and (C) the vicious cycle of decompensation — and a final-prof candidate is expected to walk an examiner through all three.[1]

A. Why pulmonary vascular resistance rises

Four parallel mechanisms push PVR up; the first two do most of the work, the last two fix it.[1]

(i) Hypoxic pulmonary vasoconstriction (the Euler-Liljestrand reflex). Locally, when an alveolus is poorly ventilated, low alveolar oxygen tension inhibits voltage-gated potassium (KV) channels on the smooth muscle of the adjacent pulmonary arteriole. The membrane depolarises, voltage-gated calcium channels open, intracellular calcium rises, and the smooth muscle contracts — diverting blood away from poorly ventilated alveoli toward well-ventilated ones (a local V/Q matching mechanism).[1]

When the hypoxia is focal this is adaptive; when it is global and chronic (as in COPD, ILD, sleep apnoea, high altitude) it produces diffuse vasoconstriction, raising PVR throughout the lung.[1]

Etymology nugget: the Euler-Liljestrand reflex is named for Ulf von Euler and Göran Liljestrand, who described in 1946 how alveolar hypoxia constricts the pulmonary arteriole — the one place in the body where hypoxia constricts rather than dilates a vessel.[1]

(ii) Loss of the pulmonary vascular bed. In emphysema the destruction of alveolar septa obliterates the capillaries that ran through them; in ILD, fibrosis obliterates small vessels. Because PVR depends on the total cross-sectional area of the pulmonary circulation, a smaller vascular bed inevitably raises PVR — even at a given blood flow.[1]

The equation governing this:[1]

• PVR = (mPAP − PCWP) / CO (Wood units)
• mPAP = PVR × CO + PCWP[1]

(iii) Secondary vascular remodelling. Chronic hypoxia and shear stress stimulate medial hypertrophy (smooth muscle thickening), intimal fibrosis, in-situ microthrombus and (rarely in Group 3, more in Group 1) plexiform lesions. These changes fix the high PVR even after oxygen is corrected — which is why prevention (early LTOT) is more effective than reversal.[1]

(iv) Secondary polycythaemia. Chronic hypoxaemia stimulates erythropoietin release from the kidney, raising haematocrit. Polycythaemia increases blood viscosity, which raises PVR (and thrombotic risk), further loading the RV.[1]

B. The RV response — hypertrophy, then dilatation, then failure

The RV is a thin-walled, compliant, low-pressure chamber — it was never built for a pressure load, and it shows. It generates forward flow largely by filling (volume change), unlike the LV which does so by contraction (pressure change).[1]

Under a chronic pressure load it passes through three stages:[1]

1. Concentric hypertrophy — increased RV wall thickness, an adaptive response to raised afterload (compensated cor pulmonale).
2. Dilatation — as PVR continues to rise and exceeds the RV's compensatory capacity, the chamber dilates, the tricuspid annulus stretches, and tricuspid regurgitation develops (now a volume as well as a pressure load).
3. Failure — RV stroke output falls; systemic venous pressure rises (raised JVP, hepatomegaly, ascites, peripheral oedema) and cardiac output falls (fatigue, exertional syncope, cool peripheries).[1]

Consultant confession: the RV is uniquely vulnerable to ischaemia. It is perfused during both systole and diastole, but at high PVR the systemic blood pressure may not exceed the rising pulmonary pressure, reducing RV coronary perfusion and producing RV ischaemia that worsens failure — a death spiral the unwary miss.[1]

C. The vicious cycle of decompensation

Once RV output falls, every step reinforces the next — which is why an acute decompensation is a medical emergency, not a ward waiting game.[1]

Tissue hypoxia worsens (driving more pulmonary vasoconstriction), renal perfusion falls (activating RAAS, retaining sodium and water, worsening congestion and oedema), and tachyarrhythmias (especially atrial flutter and fibrillation) — poorly tolerated in a stiff RV — develop.[1]

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The one-line discriminator at the bedside: bilateral crackles and orthopnoea point you to the left heart; raised JVP with clear lung fields and a loud P2 points you to the lung.[1]

What you will see at the bedside

The presentation blends the underlying lung disease with right-heart failure — and the classic patient is a middle-aged or older smoker with known COPD who develops ankle swelling, rising dyspnoea and fatigue over months.[1]

Symptoms

• Progressive exertional dyspnoea — the most common symptom, often the first sign that PH has developed on top of the lung disease.
• Fatigue, low exercise tolerance — from low cardiac output.
• Ankle and lower-limb swelling — from systemic venous congestion; may progress to sacral oedema, ascites.
• Right-upper-quadrant discomfort — from hepatic congestion (capsular stretch).
• Abdominal distension — hepatomegaly ± ascites.
• Syncope on exertion — an important red flag indicating severe PH and an inability to raise cardiac output on exercise.
• Cough, sputum, wheeze — from the underlying lung disease.[1]

Signs of right-heart failure

The right-heart failure cluster is congestion plus a low-output picture — read the JVP first, always.[1]

• Raised JVP — at rest, with prominent a waves (right atrial hypertrophy) and v waves (tricuspid regurgitation). A prominent v wave with a systolic liver pulse indicates significant TR.
• Ankle / sacral oedema.
• Hepatomegaly — smooth, tender, pulsatile if TR; a positive hepatojugular reflux.
• Ascites in advanced disease.
• Cool peripheries, low-volume pulse — from low cardiac output.[1]

Signs of pulmonary hypertension — the auscultatory cluster

Loud P2 plus a parasternal heave plus a TR murmur is the auscultatory fingerprint of pulmonary hypertension. Memorise the cluster:[1]

• Loud, palpable P2 (pulmonary component of the second heart sound) at the upper left sternal edge.
• Pulmonary ejection click and a pulmonary flow murmur (raised PA pressure).
• Graham Steell murmur — a high-pitched early diastolic murmur of pulmonary regurgitation (from dilation of the pulmonary valve ring).
• Right-sided S3 (RV failure) and S4 (RV hypertrophy).
• Tricuspid regurgitation — a pansystolic murmur at the lower left sternal edge, louder on inspiration (Carvallo's sign), with giant v waves.
• Parasternal right-ventricular heave — sustained impulse felt at the left sternal border.
• Palpable pulmonary impulse in the second left intercostal space.[1]

Etymology nugget: the Graham Steell murmur is named for the Manchester physician Graham Steell, who described it in 1888 as "a soft, blowing, well-marked diastolic murmur" in pulmonary hypertension — the high-pitched early diastolic murmur of pulmonary regurgitation from a dilated valve ring.[1]

Signs of the underlying lung disease

Look past the heart — the lungs tell you the cause. In COPD: cyanosis, barrel chest, prolonged expiration, pursed-lip breathing, use of accessory muscles, Hoover's sign (paradoxical inward movement of the lower rib margin on inspiration), biphasic wheeze, coarse basal crackles, asterixis in CO2 retention.[1]

In ILD: finger clubbing, fine Velcro-like basal crackles, reduced lung volumes. In OSA/OHS: obesity, large neck circumference, daytime somnolence.[1]

Atypical presentations — the ones that bite

The atypical presentations are the ones that get missed — and the ones the viva rewards.[1]

• The elderly patient with known COPD presenting with only unexplained ankle oedema — cor pulmonale must be considered.
• OSA / obesity hypoventilation — the patient presents with morning headache, daytime hypersomnolence, snoring, and cor pulmonale rather than the classic COPD picture.
• CTEPH — progressive dyspnoea with disproportionate exertional syncope and a prior PE/DVT; the lung fields may look normal.
• Decompensating cor pulmonale — drowsiness, asterixis, hypoxaemia, rising PaCO2, oliguria, hypotension, cool peripheries.[1]

The mimics — and the curable one you must not miss

Right-heart failure has many causes; cor pulmonale is the diagnosis only when the cause is the lung, not the left heart.[1]

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Everyone forgets: every unexplained PH needs a V/Q scan to exclude curable CTEPH. Echo alone misses organised thrombotic disease — relying on it is the recurring trainee error that costs a patient a curative pulmonary endarterectomy.[1]

The bedside round — history, examination, functional class

Focused history

The history tells you the cause before you lay a hand on the chest.[1]

• Smoking pack-years and current status; biomass-fuel exposure (a major cause in women in developing nations); occupational dusts/fumes.
• Known COPD/ILD/OSA; prior PE/DVT; current inhalers, oxygen or NIV.
• Exacerbation frequency and hospitalisations; morning headache/somnolence (OSA/OHS); syncope on exertion (severe PH).
• Vaccination history (influenza, pneumococcal); comorbidity.[1]

Focused examination

Run cardiovascular, respiratory, abdominal and neurological in that order — and read the JVP first.[1]

• Cardiovascular — JVP (height, waveform, prominent a/v waves), parasternal RV heave, palpable P2, auscultation (loud P2, pulmonary click, Graham Steell, TR murmur, RV S3/S4), hepatojugular reflux, peripheral oedema.
• Respiratory — cyanosis, clubbing (ILD), barrel chest, pursed-lip breathing, Hoover's sign, wheeze, crackles, prolonged expiration.
• Abdominal — hepatomegaly (pulsatile if TR), ascites.
• Neurological — asterixis (CO2 retention), conscious level in decompensation.[1]

Functional class (WHO/NYHA, reproduced verbatim)

The WHO/NYHA functional class is a key prognostic and follow-up marker — patients in class IV have markedly worse survival.[1]

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Investigations — echo first, catheter confirms, V/Q excludes the curable mimic

1. Echocardiography — the key first-line test

Echo is the first test you order and the test that flags PH — but it cannot definitively diagnose it. Look for:[6]

• RV hypertrophy and dilatation, a flattened/bowing interventricular septum (D-shaped LV in parasternal short axis — a sign of RV pressure overload), tricuspid regurgitation.
• Estimated RV systolic pressure (RVSP) from the peak TR jet velocity using the simplified Bernoulli equation (RVSP = 4 × v² + right atrial pressure).
• TAPSE (tricuspid annular plane systolic excursion) — a measure of RV longitudinal systolic function (under 17 mm indicates RV dysfunction).[6]

Echo also excludes left-heart disease (LV systolic/diastolic function, valve disease, raised left atrial pressure), but echocardiographic estimates of mPAP are imprecise — do not commit to a PH-specific drug on echo alone.[1]

2. Right heart catheterisation — the GOLD STANDARD

Right heart catheterisation is the only test that confirms PH, classifies the group, and gates advanced therapy.[1]

It confirms PH (mPAP over 20 mmHg), classifies pre-capillary (PCWP under 15 mmHg, PVR over 2 WU) vs post-capillary, and measures cardiac index, right atrial pressure and mixed venous O2 saturation.[1]

Pulmonary vascular resistance (PVR) = (mPAP − PCWP) / cardiac output, in Wood units (WU); PVR over 2 WU defines a pre-capillary component. The catheter also allows acute vasodilator testing (inhaled nitric oxide or IV epoprostenol) — a positive response (fall in mPAP over 10 mmHg to a normal range) identifies the small subset of Group 1 PAH patients who benefit from calcium-channel blockers. No patient in Group 3 is vasoreactive.[1]

Indications for RHC: (a) confirm PH and define the group when echo is suggestive; (b) exclude post-capillary (left-heart) PH before starting any PH-specific drug; (c) baseline before advanced therapy; (d) CTEPH workup and transplant assessment.[1]

The haemodynamic profiles that separate the groups at the catheter — the PCWP value is the single most important number, because it tells you whether the left heart is the problem:[1]

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2b. Cardiac magnetic resonance (CMR)

CMR is the reference standard for RV mass, volume and ejection fraction — more accurate than echo for the thin-walled, crescentic RV.[1]

It demonstrates RV hypertrophy, dilatation, late gadolinium enhancement of the RV insertion points (a marker of chronic pressure overload), and interventricular septal flattening, and is used for baseline and serial follow-up in specialist PH centres and to assess right-to-left shunts (phase-contrast flow).[1]

2c. Cardiopulmonary exercise testing (CPET)

CPET pins down the limiting organ system when both lung and heart disease are present. A maximal, incremental cycle test measures peak VO2, anaerobic threshold and the ventilatory equivalent for CO2 — in PH the peak VO2 is reduced and the VE/VCO2 slope is steepened (inefficient ventilation).[1]

3. ECG

The ECG cluster of cor pulmonale is high-yield exam material — right-axis deviation, P-pulmonale, RBBB, dominant R in V1.[1]

• Right-axis deviation (QRS axis over +90°).
• P-pulmonale — tall peaked P waves (over 2.5 mm) in inferior leads II, III, aVF (right atrial enlargement).
• Right bundle branch block (complete or incomplete).
• Dominant R wave in V1 (R/S ratio over 1) — RV hypertrophy criterion.
• Poor R-wave progression in anterior precordial leads.
• Right ventricular strain — T-wave inversion in V1–V3.
• S1Q3T3 pattern (in acute PE; insensitive in chronic).
• Atrial arrhythmia — atrial flutter/fibrillation, which is poorly tolerated.[1]

4. Chest X-ray

Look for enlarged central pulmonary arteries with peripheral pruning — the vascular signature of PH.[1]

• Enlarged central pulmonary arteries with peripheral pruning (loss of the normal tapering).
• Right-ventricular prominence (cardiomegaly with a lifted apex).
• Features of the underlying lung disease (hyperinflation, flat hemidiaphragms, bullae in COPD; reticulonodular changes, reduced volumes in ILD).[1]

5. Arterial blood gases

The ABG in cor pulmonale is type 2 respiratory failure with a compensated respiratory acidosis — and it tells you the LTOT need.[1]

• Type 2 respiratory failure — low PaO2 (under 60 mmHg), raised PaCO2 (over 45 mmHg).
• Compensated respiratory acidosis — pH low-normal (7.35–7.40), raised bicarbonate (over 28 mmol/L) from renal compensation.
• The degree of hypoxaemia and hypercapnia correlates with prognosis and LTOT need.[1]

6. V/Q scan — the test that finds the curable mimic

V/Q scintigraphy is the most sensitive test for CTEPH, and it is mandatory in any unexplained PH. Segmental perfusion defects with preserved ventilation (mismatch) are the signature of chronic thromboembolic disease — the surgically curable cause echo misses.[1]

7. CT pulmonary angiogram and high-resolution CT

CTPA excludes acute PE and maps central vascular anatomy; HRCT characterises the underlying lung disease.[1]

• CTPA — excludes acute PE; defines central vascular anatomy for surgical planning; less sensitive than V/Q for chronic thromboembolic disease.
• HRCT — characterises the underlying lung disease (emphysema distribution, fibrosis, bronchiectasis), assesses for vascular pruning in PH, excludes lung cancer.[1]

8. Pulmonary function tests

PFTs confirm and grade the underlying lung disease — and a reduced TLCO is a sensitive marker of PH complicating lung disease.[1]

• COPD: post-bronchodilator FEV1/FVC under 0.70; ILD: reduced FVC and TLCO.
• Reduced diffusing capacity (TLCO) is a sensitive marker of PH complicating lung disease.[1]

9. 6-minute walk test (6MWT)

Distance walked and SpO2 desaturation on the 6MWT are functional and prognostic markers. A drop in SpO2 under 88% or a walk distance under 332 m suggests significant PH.[1]

10. Blood tests

NT-proBNP screens for PH non-invasively in chronic lung disease; the rest exclude secondary causes and assess congestion.[1]

• NT-proBNP — a useful non-invasive screening marker for PH in chronic lung disease (raised in RV stretch).
• Full blood count — secondary polycythaemia (raised haematocrit) from chronic hypoxia; anaemia of chronic disease.
• U&E, LFTs — renal/hepatic congestion, hyponatraemia of advanced heart failure.
• Thyroid function, HIV, connective-tissue screen — exclude secondary causes of PH.[1]

11. Polysomnography

Polysomnography is mandatory when OSA/OHS is suspected — it confirms sleep-disordered breathing and guides CPAP/BiPAP.[1]

Acute decompensation — the ABCDE that saves the RV

Humour is off here. The acutely decompensating cor pulmonale patient — worsening hypoxaemia, rising PaCO2, drowsiness, oliguria, hypotension — is a medical emergency. Run the ABCDE approach without deviation:[1]

1. Airway / Breathing — assess and secure.
2. Controlled oxygen — target SpO2 88–92% in chronic CO2 retainers (see Pitfalls below). Use a Venturi mask (24% or 28%) for a predictable inspired oxygen concentration.
3. Repeat ABG at 30–60 minutes after any change in oxygen or ventilation.
4. Non-invasive ventilation (BiPAP) — start for acute hypercapnic respiratory failure (pH under 7.35 with PaCO2 over 45 mmHg despite controlled oxygen). Settings: IPAP 10–15 cmH2O, EPAP 4–5 cmH2O, titrate upwards.
5. Intravenous diuretics — furosemide 20–40 mg IV for volume overload; cautious (see Pitfalls).
6. Treat reversible triggers — pneumonia, exacerbation, arrhythmia, PE.
7. Treat poorly-tolerated atrial flutter/fibrillation — rate-control (digoxin, cautious calcium-channel blocker), anticoagulation, consideration of cardioversion.
8. Invasive mechanical ventilation — last resort; the raised intrathoracic pressure worsens RV afterload and may precipitate cardiovascular collapse. Use lung-protective ventilation, avoid hyperinflation, ensure adequate preload.[1]

The classic iatrogenic pitfall — CO2 narcosis from excessive oxygen

The classic trap in this disease is the CO2 retainer who is given high-flow oxygen to target normoxia. In chronic CO2 retainers, excessive oxygen risks CO2 narcosis via two mechanisms:[1]

• V/Q mismatch — oxygen taken up by previously hypoxic-vessels-constricted alveoli increases perfusion of low-V/Q units.
• The Haldane effect — oxygen binding to haemoglobin displaces CO2 from carbamino groups and reduces CO2 carriage as bicarbonate, releasing CO2 into venous blood.[1]

Always use controlled oxygen (target SpO2 88–92%) in suspected CO2 retainers.[1]

Definitive management — treat the lung, give the oxygen, fix the ventilation

Pillar 1 — Treat the underlying lung disease

The single most important pillar: treat the lung, because the lung is the cause.[1]

• COPD — dual bronchodilation (LAMA + LABA; e.g. tiotropium 18 microgram once daily + a LABA such as formoterol); add ICS only if blood eosinophils over 300 or frequent exacerbations; pulmonary rehabilitation; influenza and pneumococcal vaccination; smoking cessation (the only disease-modifying intervention — nicotine replacement, varenicline 0.5 mg daily titrated to 1 mg twice daily, bupropion 150 mg daily).
• ILD — disease-specific therapy (e.g. antifibrotics pirfenidone and nintedanib for IPF), immunosuppression for inflammatory ILD; refer for transplant in advanced disease.
• OSA / obesity hypoventilation — CPAP (or BiPAP for daytime hypercapnia) and weight reduction (bariatric surgery in selected OHS).[1]

Pillar 2 — Long-term oxygen therapy (LTOT)

LTOT is the one intervention in cor pulmonale with a proven survival benefit — and it works by turning off the hypoxic vasoconstriction.[1]

• Criteria (per the MRC and NOTT trials): PaO2 under 55 mmHg (under 7.3 kPa) on room air on two stable occasions, OR PaO2 under 59 mmHg (under 7.8 kPa) with evidence of cor pulmonale or secondary polycythaemia.
• Prescription — oxygen for at least 15 hours/day (ideally approaching 24 h), via concentrator, at a flow that raises PaO2 to at least 60 mmHg (over 8 kPa) without worsening CO2.[1][2]

Survival benefit — the two trials every candidate must name: the MRC trial (1981, PMID 6110912) showed domiciliary oxygen for about 15 h/day reduced mortality versus no oxygen in chronic hypoxic cor pulmonale; the NOTT trial (1980, PMID 6776858) showed continuous oxygen (about 24 h/day) halved mortality versus nocturnal-only (12 h).[2][3]

The mechanism of benefit: corrects the hypoxic pulmonary vasoconstriction driving the RV overload; partially reverses PH and polycythaemia; reduces the afterload on the RV.[1]

Pillar 3 — Optimise ventilation

NIV and CPAP turn off nocturnal hypoxia and hypercapnia — and in OSA the PH is often reversible if treated early.[1]

• NIV (BiPAP) — for chronic hypercapnia (PaCO2 over 50 mmHg, especially with nocturnal hypoventilation), OHS, neuromuscular disease, kyphoscoliosis. Reduces PVR, lowers RV load, improves sleep quality and survival.
• CPAP — for obstructive sleep apnoea. Abolishes nocturnal hypoxia, often reversing the PH if treated early.
• Both are part of the treat-the-lungs philosophy that distinguishes cor pulmonale management from left-heart failure.[1]

Pillar 4 — Right-heart failure, oedema, arrhythmia

Diurese cautiously, never reach for an ACE inhibitor or beta-blocker, and never reach for a routine pulmonary vasodilator in Group 3.[1]

• Cautious diuretics — furosemide 20–40 mg orally once daily, titrated to clinical euvolaemia. Monitor renal function and blood pressure; the RV is preload-dependent — over-diuresis lowers cardiac output.
• No role for ACE inhibitors / beta-blockers as routine therapy in cor pulmonale (unlike LV failure); they may worsen hypotension and have no proven survival benefit.
• Atrial fibrillation/flutter — rate-control (digoxin, cautious beta-blocker/calcium-channel blocker), rhythm-control, anticoagulation with CHA2DS2-VASc.
• Secondary polycythaemia — venesection only if symptomatic hyperviscosity (haematocrit over 56%) — not routinely.
• Pulmonary vasodilators in Group 3 PH — generally NOT recommended in COPD/ILD (e.g. bosentan, sildenafil, riociguat) — they worsen V/Q mismatch and hypoxaemia without proven benefit; considered only in selected, severe cases under a specialist PH centre.
• Calcium-channel blockers — NOT useful in Group 3 PH (no acute vasodilator response, unlike idiopathic PAH).[1]

The classic trap: routine pulmonary vasodilators do NOT help in Group 3 — treat the lung and the hypoxia. Diffuse pulmonary vasodilation opens up poorly ventilated units (worsened low-V/Q shunt), lowers PaO2, while the fixed vascular loss is unaffected — so symptoms and prognosis do not improve.[1]

Pillar 4b — Pulmonary vasodilator / PH-specific therapy: the full drug ladder

An examiner will ask you to name the classes of pulmonary hypertension drug — but the answer is always the same caveat: these are built for Group 1 PAH, NOT routine for Group 3.[1]

The 2022 ESC/ERS Guidelines define a tiered pharmacology built almost entirely for Group 1 PAH; these agents are the standard of care in PAH but are generally NOT used in Group 3 (lung disease) PH, because non-selective pulmonary vasodilation worsens intrapulmonary V/Q matching and systemic hypoxaemia without proven benefit.[1]

[1]

Why these are NOT routine in cor pulmonale (Group 3): in COPD and ILD the hypoxia is the driver and the vascular bed is structurally damaged. Diffuse vasodilation opens up poorly ventilated units (worsened low-V/Q shunt), lowers PaO2, while the fixed vascular loss is unaffected — so symptoms and prognosis do not improve. The RISE-IIP (riociguat in ILD-PH) and earlier sildenafil trials gave mixed or negative results; current evidence supports their use in Group 3 only in highly selected, severe, progressive cases under a specialist PH centre.[4]

The single exception that an examiner rewards: riociguat is licensed for inoperable or persistent CTEPH (Group 4), and pulmonary endarterectomy can cure it. Inhaled treprostinil has shown benefit in PH due to ILD but remains a specialist-centre decision.[5][4]

Pillar 5 — Lung transplantation

Transplant is offered before the RV fails irreversibly — because the RV reverse-remodels dramatically once the hypoxic lung is gone.[1]

Considered in end-stage cor pulmonale from ILD (IPF), COPD, or cystic fibrosis when medical therapy fails and the RV failure is still potentially reversible — the transplanted lung(s) remove the hypoxic/vascular load and the RV recovers. A pre-transplant RHC is mandatory; severely fixed RV failure with multi-organ dysfunction may need heart-lung transplantation rather than bilateral lung alone.[1]

Specific treatment of CTEPH — the surgically curable cause

CTEPH is the only surgically curable cause of PH — pulmonary endarterectomy can restore near-normal pulmonary pressures in survivors.[1]

• Lifelong anticoagulation (warfarin or DOAC).
• Pulmonary endarterectomy (PEA) — the potentially curative operation for operable, accessible organised thrombus in the main/lobar/segmental pulmonary arteries; performed at a specialist centre.
• Riociguat (soluble guanylate cyclase stimulator) — for non-operable or persistent CTEPH; 1 mg three times daily, titrated.
• Balloon pulmonary angioplasty (BPA) — for inoperable distal disease.
• Operability is decided at a specialist CTEPH multidisciplinary team — depends on thrombus accessibility (proximal main/lobar is operable; distal segmental/subsegmental is not), the haemodynamic burden, and surgical fitness. A pre-operative pulmonary angiogram (not CTPA) maps the organised thrombus. PEA mortality in expert centres is under 5 per cent.
• Residual/persistent PH after PEA or inoperable disease is treated with riociguat and staged BPA. Anticoagulation continues lifelong; the optimal agent in CTEPH remains debated (warfarin historically preferred; DOACs increasingly used).[1][5]

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The subtypes you will meet on the wards

Each subtype has one teaching point — and one examiner-favourite twist.[1]

• COPD with cor pulmonale — the prototype. LTOT, NIV if hypercapnic, optimise inhalers, treat exacerbations aggressively, smoking cessation.
• Cor pulmonale in ILD (IPF) — restrictive, hypoxic; often severe PH in advanced disease. Vasodilators generally avoided (worsen hypoxaemia); refer early for lung transplantation.
• Cor pulmonale in OSA / obesity hypoventilation syndrome — CPAP/BiPAP plus weight loss; PH is often reversible if treated early.
• Cor pulmonale in CTEPH — the only surgically curable cause; V/Q mandatory in every unexplained PH; PEA, riociguat or BPA.
• Cor pulmonale in kyphoscoliosis / neuromuscular disease — restrictive chest-wall disease; long-term NIV.
• Acute cor pulmonale from massive PE — a different entity (sudden RV overload); anticoagulation, thrombolysis, embolectomy.
• High-altitude cor pulmonale (chronic mountain sickness / Monge's disease) — chronic hypoxia at altitude; descent or supplemental oxygen; venesection for polycythaemia.[1]

Complications and the pitfalls that hurt patients

Complications

Once severe RV failure is established, the downstream damage is multisystem — and the prognosis is poor without intervention.[1]

• Worsening right-heart failure — refractory oedema, ascites, anasarca.
• Atrial arrhythmia — atrial flutter/fibrillation, poorly tolerated.
• Secondary polycythaemia — from chronic hypoxia; raises viscosity and thrombotic risk.
• Venous thromboembolism and pulmonary embolism — increased risk from immobility and polycythaemia.
• Cardiorenal syndrome — type 2 (chronic), rising creatinine from renal congestion and low cardiac output.
• Hepatorenal dysfunction — congestive hepatopathy ("nutmeg liver"), fibrosis, coagulopathy.
• Death — once severe RV failure is established, prognosis is poor without intervention.[1]

The classic iatrogenic pitfalls (high-yield)

These are the six errors that hurt cor pulmonale patients — every candidate must name all six.[1]

1. CO2 narcosis from high-flow oxygen in a chronic CO2 retainer — always target SpO2 88–92%.
2. Over-diuresis — lowers preload, reduces RV stroke output (RV is preload-dependent), worsens renal function.
3. Indiscriminate pulmonary vasodilators in COPD/ILD — worsen V/Q mismatch and hypoxaemia.
4. Missing CTEPH — a surgically curable cause overlooked if only an echo is done without a V/Q scan.
5. Calcium-channel blockers without an acute vasodilator study — useless in Group 3 PH and may cause hypotension.
6. Diagnosing cor pulmonale without excluding left-heart disease — post-capillary PH (Group 2) is treated very differently.[1]

Ward-round test — three stems, thirty seconds each

Stem 1 — the COPD smoker with ankle swelling (answer)

A 68-year-old man with 50 pack-years of smoking and GOLD 3 COPD presents with three months of ankle swelling, exertional dyspnoea, and a JVP at 6 cm with a loud P2 and a parasternal heave. Echo shows RV dilatation with a D-shaped septum and raised estimated RVSP; the LV is normal. What is the diagnosis, the key investigation, and the first disease-modifying treatment? Model: This is chronic cor pulmonale (WHO Group 3 PH) — right-heart failure from lung disease with a normal left heart. Confirm with right heart catheterisation (mPAP over 20 mmHg, PCWP under 15 mmHg, PVR over 2 WU) and check ABGs. The first disease-modifying step is long-term oxygen therapy for at least 15 hours/day if PaO2 is under 55 mmHg — the MRC and NOTT trials showed a survival benefit by reversing hypoxic pulmonary vasoconstriction. Treat the COPD, optimise ventilation with NIV if hypercapnic, diurese cautiously, and do not reach for a routine pulmonary vasodilator — it worsens V/Q mismatch in Group 3.[1][2]

Stem 2 — unexplained PH with exertional syncope and a prior PE (answer)

A 55-year-old woman presents with six months of progressive dyspnoea and two episodes of exertional syncope. She had a pulmonary embolism 18 months ago. Echo shows raised RVSP with RV dilatation; the lung fields are clear and PFTs are near-normal. What is the diagnosis you must exclude, and what is the single most sensitive test? Model: This is chronic thromboembolic pulmonary hypertension (CTEPH, WHO Group 4) until proven otherwise — exertional syncope with a prior PE is the classic presentation, and it is the only surgically curable cause of PH. Everyone forgets: every unexplained PH needs a V/Q scan to exclude curable CTEPH — echo alone misses organised thrombotic disease, and CTPA is less sensitive than V/Q for chronic thromboembolic disease. Confirm segmental perfusion defects with mismatch, then refer to a specialist CTEPH team for pulmonary angiography and consideration of pulmonary endarterectomy (potentially curative; mortality under 5 per cent in expert centres). Lifelong anticoagulation; riociguat or BPA if inoperable.[1][5]

Stem 3 — the OHS patient with morning headache and oedema (answer)

A 50-year-old woman with a BMI of 42 presents with morning headache, daytime hypersomnolence, loud snoring, and ankle swelling. ABGs show PaO2 of 58 mmHg, PaCO2 of 52 mmHg, and a raised bicarbonate. What is the diagnosis, and why is oxygen alone not the answer? Model: This is obesity hypoventilation syndrome (OHS) with cor pulmonale — chronic hypercapnia and hypoxaemia from sleep-disordered breathing driving PH and right-heart failure. Oxygen alone does not fix the problem because the driver is nocturnal hypoventilation, not just low inspired oxygen; giving oxygen without ventilation risks worsening CO2 retention. The disease-modifying treatment is CPAP (or BiPAP if daytime hypercapnia) plus weight reduction — and the PH is often reversible if treated early. Confirm with polysomnography, optimise ventilation, and reassess.[1]

Prognosis, disposition, and the markers that set both

Prognostic markers

These are the markers that tell you the RV is failing — and the ones an examiner expects you to list.[1]

• WHO/NYHA functional class — class IV markedly worse.
• 6-minute-walk distance — under 332 m suggests significant disease.
• Right-ventricular function — TAPSE under 17 mm, RV dilatation, pericardial effusion (poor prognostic markers).
• NT-proBNP — higher is worse.
• Haemodynamics (RHC) — right atrial pressure over 8 mmHg, cardiac index under 2.5 L/min/m², mixed venous O2 saturation under 60%.
• Underlying disease — COPD with chronic hypoxaemia, severe IPF, CTEPH.[1]

Survival and what improves it

5-year survival in PH complicating COPD/ILD is poor once RV failure is established — but four interventions change the trajectory.[1]

• LTOT (MRC, NOTT) and optimised ventilation (NIV/CPAP) improve survival.
• Pulmonary endarterectomy can cure CTEPH.
• Smoking cessation slows the underlying COPD.[1]

Follow-up

Multidisciplinary respiratory / PH clinic; serial echocardiography and NT-proBNP; repeat 6MWT; optimise underlying disease; vaccination; written action plan for decompensation.[1]

Special populations — where the rules bend

Examiners use these scenarios heavily — pregnancy in particular carries a mortality worth quoting.[1]

• Elderly — multimorbidity, polypharmacy; may present with only ankle oedema; beware over-diuresis and drug interactions.
• Pregnancy — pulmonary hypertension carries a high maternal mortality (30–56% historically); counsel against pregnancy; manage in a specialist PH-obstetric clinic if pregnancy occurs.
• Obesity hypoventilation syndrome / OSA — BMI over 30, daytime hypercapnia, sleep-disordered breathing; CPAP/BiPAP and weight loss; PH is often reversible.
• Children — bronchopulmonary dysplasia, cystic fibrosis-related PH, congenital lung disease.
• Patients already on anticoagulants — balance bleeding vs thrombosis in CTEPH; lifelong anticoagulation is needed regardless.
• Perioperative — patients with cor pulmonale carry high perioperative risk; optimise oxygenation and ventilation, avoid hypoxia/hypercapnia and over-sedation; consider invasive monitoring.[1]

Evidence, guidelines and regional differences

The 2022 ESC/ERS Guidelines are the current global reference — and the two oxygen trials from 1980–81 are the bedrock evidence every candidate must name.[1]

• 2022 ESC/ERS PH Guidelines (Humbert et al., PMID 36017548) — current global reference. Revised the diagnostic threshold (mPAP over 20 mmHg, down from over 25 mmHg) and introduced PVR over 2 WU for pre-capillary PH. Stratifies PH into the five WHO groups.[1]
• MRC trial (1981, PMID 6110912) — established that domiciliary oxygen for about 15 h/day improved survival in chronic hypoxic cor pulmonale complicating chronic bronchitis/emphysema.[2]
• NOTT (1980, PMID 6776858) — showed continuous oxygen (about 24 h/day) halved mortality compared with nocturnal-only (12 h/day) in hypoxaemic COPD.[3]
• NICE NG115 (COPD) and GOLD 2024 — recommend LTOT, NIV, and the treat-the-lung approach; reaffirm the controlled-oxygen target SpO2 88–92%.
• BTS home oxygen guidance — practical delivery of LTOT in the community.
• Regional deltas — drug availability and naming differ (e.g. riociguat widely available; roflumilast for COPD exacerbators; access to pulmonary endarterectomy is centralised).[1]

Controversy — pulmonary vasodilators in Group 3 PH. Current evidence does NOT support routine use in COPD/ILD; trials (e.g. RISE-IIP in ILD-PH, INCREASE in ILD-PH) are mixed. Specialist PH centres may use them in selected, severe, progressive cases.[4]

Controversy — the 2022 mPAP threshold change. Lowering the threshold from over 25 to over 20 mmHg and adding the PVR cut-off reclassified many patients; some clinicians worry about over-diagnosis, but the 2022 guidance is now the global standard.[1]

Exam pearls

• Cor pulmonale = RV hypertrophy then failure from lung disease via pulmonary hypertension (WHO Group 3 PH).
• Commonest cause is COPD; other big causes — ILD, OSA/OHS, CTEPH, restrictive chest-wall disease.
• Mechanism: hypoxic pulmonary vasoconstriction (Euler-Liljestrand reflex — KV channel inhibition, Ca²⁺ influx) plus loss of the vascular bed → raised PVR.
• Bedside cluster: loud P2, RV heave, raised JVP, TR murmur (Carvallo's sign), hepatomegaly, ankle oedema.
• ECG cluster: right-axis deviation, P-pulmonale, RBBB, dominant R in V1, poor R-wave progression.
• Echo: RV hypertrophy/dilatation, D-shaped septum, TR, raised RVSP; right heart catheterisation is the gold standard.
• Haemodynamics (2022 ESC/ERS): PH = mPAP over 20 mmHg; pre-capillary = PCWP under 15 mmHg + PVR over 2 WU.
• LTOT for at least 15 h/day improves survival when PaO2 under 55 mmHg — MRC and NOTT trials.
• Controlled oxygen target SpO2 88–92% in CO2 retainers (avoid CO2 narcosis — Haldane effect, V/Q mismatch).
• Every unexplained PH needs a V/Q scan to find surgically curable CTEPH — pulmonary endarterectomy.
• Avoid over-diuresis (RV is preload-dependent); avoid routine vasodilators/CCBs in COPD/ILD Group 3 PH (worsen V/Q mismatch).
• NT-proBNP is a useful non-invasive screening marker for PH in chronic lung disease.
• Pregnancy in PH carries high maternal mortality — counsel against.[1]

[1]

The mantra

The mantra: Treat the lung, give the oxygen, fix the ventilation — and scan for CTEPH in every unexplained case.[1]

[1]

References

1. [1]Humbert M, Kovacs G, Hoeper MM, et al. 2022 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension Eur Heart J, 2022.PMID 36017548
2. [2]Medical Research Council Working Party. Long term domiciliary oxygen therapy in chronic hypoxic cor pulmonale complicating chronic bronchitis and emphysema. Report of the Medical Research Council Working Party Lancet, 1981.PMID 6110912
3. [3]Nocturnal Oxygen Therapy Trial Group. Continuous or nocturnal oxygen therapy in hypoxemic chronic obstructive lung disease: a clinical trial. Nocturnal Oxygen Therapy Trial Group Ann Intern Med, 1980.PMID 6776858
4. [4]Waxman A, Restrepo-Jaramillo R, Thenappan T, et al. Inhaled Treprostinil in Pulmonary Hypertension Due to Interstitial Lung Disease. N Engl J Med, 2021.PMID 33440084
5. [5]Ghofrani HA, D'Armini AM, Grimminger F, et al. Riociguat for the treatment of chronic thromboembolic pulmonary hypertension. N Engl J Med, 2013.PMID 23883377
6. [6]Mukherjee M, Rudski LG, Addetia K, et al. Guidelines for the Echocardiographic Assessment of the Right Heart in Adults and Special Considerations in Pulmonary Hypertension: Recommendations from the American Society of Echocardiography. J Am Soc Echocardiogr, 2025.PMID 40044341