What is cor pulmonale?

What is Cor Pulmonale

Cor pulmonale is right ventricular enlargement (hypertrophy and/or dilation) secondary to pulmonary hypertension caused by diseases affecting the structure or function of the lungs, which may progress to right heart failure. 1, 2, 3

Definition and Core Pathophysiology

• Cor pulmonale specifically refers to right ventricular structural changes resulting from elevated pulmonary vascular resistance (PVR) due to respiratory system disorders, not left heart disease or congenital heart disease 2, 3, 4
• The condition represents "pre-capillary" pulmonary hypertension, meaning the elevated pressure occurs before the pulmonary capillaries, distinguishing it from left heart disease 2
• The right ventricle is coupled to the normally low-resistance, high-compliance pulmonary circulation and adapts poorly to acute pressure increases compared to volume changes 1

Hemodynamic Characteristics

Typical Severity in Chronic Respiratory Disease

• In chronic obstructive pulmonary disease (COPD), the most common cause, pulmonary artery mean pressure (PAP) typically ranges between 20-35 mmHg at rest in stable disease—representing mild to moderate pulmonary hypertension 2
• A minority (<5%) of COPD patients develop "severe" or "disproportionate" pulmonary hypertension with PAP >40 mmHg, though the mechanism remains poorly understood 2, 5
• The severity of pulmonary hypertension correlates poorly with the severity of underlying lung disease, making clinical suspicion critical 5

Dynamic Worsening

• Pulmonary artery pressure may worsen acutely during exercise, sleep, and disease exacerbations 2
• These acute afterload increases can precipitate right heart failure even when resting pressures are only mildly elevated 2

Primary Etiologies

Most Common Causes

• Chronic obstructive pulmonary disease (COPD) is by far the leading cause, accounting for the majority of cases 2, 4
• Idiopathic pulmonary fibrosis and other interstitial lung diseases 2, 4
• Obesity-hypoventilation syndrome 2
• Sleep-disordered breathing 1

Other Respiratory Causes

• Chronic exposure to high altitude 1
• Alveolar hypoventilation disorders 1
• Neuromuscular diseases affecting ventilation 4
• Thoracic cage disorders 4

Vascular Causes

• Chronic thromboembolic pulmonary disease 3, 6
• Multiple pulmonary emboli 4

Pathophysiologic Mechanisms

Primary Driver: Chronic Alveolar Hypoxia

• Chronic, long-standing alveolar hypoxia is the major determinant of elevated PAP and PVR 2
• Hypoxia induces pulmonary vascular remodeling through hypoxic pulmonary vasoconstriction 2, 4

Contributing Factors

• Arterial hypoxemia and resultant polycythemia increase blood viscosity and afterload 3
• Hypercapnia and respiratory acidosis contribute to increased right ventricular afterload 3
• Mechanical narrowing and obstruction of the pulmonary vascular bed 4

Right Ventricular Adaptation and Failure

Compensated Phase:

• The hypertrophied right ventricle develops isovolumic contraction and relaxation phases with increased systolic pressure and higher end-diastolic volume 1

Decompensated Phase:

• Concomitant rise in PVR and right atrial pressure occurs 1
• Cardiac output subsequently declines, followed by reduction in PAP—declining PAP in the setting of high PVR is an ominous clinical finding 1
• Right ventricular dilation promotes tricuspid regurgitation, which exacerbates dilation 1

Ventricular Interdependence

• Right ventricular dilation causes leftward shift of the interventricular septum, increasing left ventricular end-diastolic pressure while reducing transmural filling pressure 1
• This impedes left ventricular diastolic filling and contributes to systemic hypoperfusion 1
• Within the confined pericardial space, right ventricular dilation compresses the left ventricular cavity, equalizing biventricular diastolic pressures 1

Clinical Indicators of Disproportionate Pulmonary Hypertension

Suspect severe or disproportionate pulmonary hypertension when:

• Disproportionately low diffusion capacity (DLCO) relative to spirometry 5
• Presence of hypocapnia (low PaCO2) 5
• Clinical deterioration exceeds what would be expected from FEV1 alone 5
• Symptoms are more severe than predicted by pulmonary function tests 5

Diagnostic Approach

Physical Examination Findings

• Left parasternal lift (right ventricular heave) 1, 7
• Accentuated pulmonary component of second heart sound 1, 7
• Right ventricular third heart sound 1
• Pansystolic murmur of tricuspid regurgitation 1
• Diastolic murmur of pulmonary regurgitation 1
• Elevated jugular venous pressure, hepatomegaly, ascites, peripheral edema, and cool extremities in advanced disease 1

Important caveat: Physical examination has poor sensitivity for detecting moderate cor pulmonale, particularly in obese patients 7

Echocardiographic Criteria (Gold Standard for Screening)

Right Ventricular Enlargement:

• Right ventricle/left ventricle basal diameter ratio >1.0 7
• Right atrial area (end-systole) >18 cm² 7

Pressure Overload Indicators:

• Flattening of interventricular septum (left ventricular eccentricity index >1.1 in systole and/or diastole) 7
• Tricuspid regurgitation velocity >3.4 m/s (corresponding to PA systolic pressure >50 mmHg) indicates likely pulmonary hypertension 7
• Right ventricular outflow Doppler acceleration time <105 msec and/or midsystolic notching suggests increased PVR 7
• Early diastolic pulmonary regurgitation velocity >2.2 m/sec indicates elevated pulmonary artery pressure 7

Severity Grading:

• No cor pulmonale: Tricuspid regurgitation velocity ≤2.8 m/s, PA systolic pressure ≤36 mmHg 7
• Mild cor pulmonale: Tricuspid regurgitation velocity 2.9–3.4 m/s, PA systolic pressure 37–50 mmHg 7
• Moderate to severe cor pulmonale: Tricuspid regurgitation velocity >3.4 m/s, PA systolic pressure >50 mmHg 7

Additional Findings:

• Inferior vena cava diameter >21 mm with decreased inspiratory collapse (<50% with sniff or <20% with quiet inspiration) suggests elevated right atrial pressure 7
• Pulmonary artery diameter >25 mm suggests pulmonary hypertension 7

Critical limitation: Echocardiographic assessment may be challenging in patients with hyperinflated lungs due to COPD, though subcostal views usually provide adequate visualization 7. Accuracy is low in advanced respiratory disease, and correlation with measured PA systolic pressure is insufficient for precise estimation in individual patients 5

Right Heart Catheterization

• Remains the gold standard for confirming pulmonary hypertension with mean PAP ≥25 mmHg 7, 5
• The only method for accurately measuring pulmonary vascular pressures 5
• Indicated for diagnosis or exclusion of pulmonary hypertension in candidates for surgical treatments (lung transplantation, lung volume reduction surgery) 5
• Not recommended for routine use since similar prognostic information can be obtained from simpler measurements like FEV1 and arterial blood gases 5

Electrocardiographic Findings

• Right axis deviation for age 7
• Right atrial enlargement (P pulmonale) 1
• Right ventricular hypertrophy 1, 7
• Right ventricular strain pattern 1
• Right bundle branch block 1
• QTc prolongation (suggests severe disease) 1

Acute cor pulmonale patterns (e.g., from pulmonary embolism):

• S1Q3T3 pattern 7
• S1S2S3 pattern 7
• Negative T waves in right precordial leads 7
• Transient right bundle branch block 7
• Pseudoinfarction pattern 7

Chest Radiography

• Central pulmonary arterial dilatation with peripheral vascular "pruning" 1, 7
• Right atrial and right ventricular enlargement in advanced cases 1
• Right interlobar artery enlargement 7
• In COPD: lung hyperinflation and hyperlucent areas with peripheral trimming of vascular markings 7

Advanced Imaging

• CT chest: Pulmonary artery/ascending aorta diameter ratio ≥0.93 has high predictive value for severe pulmonary hypertension when combined with echocardiographic PA systolic pressure and plasma NT-proBNP 5
• MRI: Valuable for assessing right ventricular size and function, evaluating septal flattening, and detecting delayed contrast enhancement of septal insertions 7

Common Clinical Pitfalls

• Do not rely solely on physical examination to exclude moderate cor pulmonale, as sensitivity is poor 7
• Do not assume pulmonary hypertension severity correlates with lung disease severity—always investigate when clinical deterioration seems disproportionate 5
• Recognize that declining PAP with persistently elevated PVR indicates decompensation, not improvement 1
• Do not overlook cor pulmonale in obese patients where physical findings may be masked 7
• Awake oxygen saturation does not predict hypoxemia during sleep, which can worsen pulmonary hypertension 7

Modern Context

The term "cor pulmonale" is less frequently used in modern practice as a synonym for right heart failure, since long-term oxygen therapy and aggressive ventilation optimization have reduced the incidence of overt right heart failure 8. The right heart is now recognized not as an "innocent bystander" but as a key component in pulmonary hypertension pathophysiology, with right heart function status being a major determinant of outcome 8.